Prescription Drugs

CLINICAL PHARMACOLOGY Thyroid hormone synthesis and secretion is regulated by the hypothalamic-pituitarythyroid axis. Thyrotropin-releasing hormone (TRH) released from the hypothalamus stimulates secretion of thyrotropin-stimulating hormone, TSH, from the anterior pituitary. TSH, in turn, is the physiologic stimulus for the synthesis and secretion of thyroid hormones, L-thyroxine (T4) and L-triiodothyronine (T3), by the thyroid gland. Circulating serum T3 and T4 levels exert a feedback effect on both TRH and TSH secretion. When serum T3 and T4 levels increase, TRH and TSH secretion decrease. When thyroid hormone levels decrease, TRH and TSH secretion increase. The mechanisms by which thyroid hormones exert their physiologic actions are not completely understood, but it is thought that their principal effects are exerted through control of DNA transcription and protein synthesis. T3 and T4 diffuse into the cell nucleus and bind to thyroid receptor proteins attached to DNA. This hormone nuclear receptor complex activates gene transcription and synthesis of messenger RNA and cytoplasmic proteins. Thyroid hormones regulate multiple metabolic processes and play an essential role in normal growth and development, and normal maturation of the central nervous system and bone. The metabolic actions of thyroid hormones include augmentation of cellular respiration and thermogenesis, as well as metabolism of proteins, carbohydrates and lipids. The protein anabolic effects of thyroid hormones are essential to normal growth and development. The physiologic actions of thyroid hormones are produced predominately by T3, the majority of which (approximately 80%) is derived from T4 by deiodination in peripheral tissues. Levothyroxine, at doses individualized according to patient response, is effective as replacement or supplemental therapy in hypothyroidism of any etiology, except transient hypothyroidism during the recovery phase of subacute thyroiditis. Levothyroxine is also effective in the suppression of pituitary TSH secretion in the treatment or prevention of various types of euthyroid goiters, including thyroid nodules, Hashimoto's thyroiditis, multinodular goiter and, as adjunctive therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer (see INDICATIONS AND USAGE, PRECAUTIONS, DOSAGE AND ADMINISTRATION). Pharmacokinetics Absorption Absorption of orally administered T4 from the gastrointestinal (GI) tract ranges from 40% to 80%. The majority of the levothyroxine dose is absorbed from the jejunum and upper ileum. The relative bioavailability of UNITHROID tablets, compared to an equal nominal dose of oral levothyroxine sodium solution, is approximately 99%. T4 absorption is increased by fasting, and decreased in malabsorption syndromes and by certain foods such as soybean infant formula. Dietary fiber decreases bioavailability of T4. Absorption may also decrease with age. In addition, many drugs and foods affect T4 absorption (see PRECAUTIONS: DRUG INTERACTIONS and Drug-Food Interactions). Distribution Circulating thyroid hormones are greater than 99% bound to plasma proteins, including thyroxine-binding globulin (TBG), thyroxine-binding prealbumin (TBPA), and albumin (TBA), whose capacities and affinities vary for each hormone. The higher affinity of both TBG and TBPA for T4 partially explains the higher serum levels, slower metabolic clearance, and longer half-life of T4 compared to T3. Protein-bound thyroid hormones exist in reverse equilibrium with small amounts of free hormone. Only unbound hormone is metabolically active. Many drugs and physiologic conditions affect the binding of thyroid hormones to serum proteins (seePRECAUTIONS: DRUG INTERACTIONSand Drug-Laboratory Test Interactions). Thyroid hormones do not readily cross the placental barrier (see PRECAUTIONS, Pregnancy). Metabolism T4 is slowly eliminated (see TABLE 1). The major pathway of thyroid hormone metabolism is through sequential deiodination. Approximately eighty-percent of circulating T3 is derived from peripheral T4 by monodeiodination. The liver is the major site of degradation for both T4 and T3; with T4 deiodination also occurring at a number of additional sites, including the kidney and other tissues. Approximately 80% of the daily dose of T4 is deiodinated to yield equal amounts of T3 and reverse T3 (rT3). T3 and rT3 are further deiodinated to diiodothyronine. Thyroid hormones are also metabolized via conjugation with glucuronides and sulfates and excreted directly into the bile and gut where they undergo enterohepatic recirculation. Elimination Thyroid hormones are primarily eliminated by the kidneys. A portion of the conjugated hormone reaches the colon unchanged and is eliminated in the feces. Approximately 20% of T4 is eliminated in the stool. Urinary excretion of T4 decreases with age. Table 1: Pharmacokinetic Parameters of Thyroid Hormones in Euthyroid Patients Hormone Ratio in Thyroglobulin Biologic Potency t½ (days) Protein Binding (%)2 Levothyroxine (T4) 10 - 20 1 6-71 99.96 Liothyronine (T3) 1 4 < 2 99.5 1 3 to 4 days in hyperthyroidism, 9 to 10 days in hypothyroidism; 2 Includes TBG, TBPA, and TBA

CLINICAL PHARMACOLOGY Thyroid hormone synthesis and secretion is regulated by the hypothalamic-pituitary-thyroid axis. Thyrotropin-releasing hormone (TRH) released from the hypothalamus stimulates secretion of thyrotropin-stimulating hormone, TSH, from the anterior pituitary. TSH, in turn, is the physiologic stimulus for the synthesis and secretion of thyroid hormones, L-thyroxine (T4 ) and L-triiodothyronine (T3 ), by the thyroid gland. Circulating serum T3 and T4 levels exert a feedback effect on both TRH and TSH secretion. When serum T3 and T4 levels increase, TRH and TSH secretion decrease. When thyroid hormone levels decrease, TRH and TSH secretion increase. The mechanisms by which thyroid hormones exert their physiologic actions are not completely understood, but it is thought that their principal effects are exerted through control of DNA transcription and protein synthesis. T3 and T4 diffuse into the cell nucleus and bind to thyroid receptor proteins attached to DNA. This hormone nuclear receptor complex activates gene transcription and synthesis of messenger RNA and cytoplasmic proteins. Thyroid hormones regulate multiple metabolic processes and play an essential role in normal growth and development, and normal maturation of the central nervous system and bone. The metabolic actions of thyroid hormones include augmentation of cellular respiration and thermogenesis, as well as metabolism of proteins, carbohydrates and lipids. The protein anabolic effects of thyroid hormones are essential to normal growth and development. The physiological actions of thyroid hormones are produced predominantly by T3, the majority of which (approximately 80%) is derived from T4 by deiodination in peripheral tissues. Levothyroxine, at doses individualized according to patient response, is effective as replacement or supplemental therapy in hypothyroidism of any etiology, except transient hypothyroidism during the recovery phase of subacute thyroiditis. Levothyroxine is also effective in the suppression of pituitary TSH secretion in the treatment or prevention of various types of euthyroid goiters, including thyroid nodules, Hashimoto's thyroiditis, multinodular goiter and, as adjunctive therapy in the management of thyrotropin-dependent welldifferentiated thyroid cancer (see INDICATIONS AND USAGE, PRECAUTIONS, and DOSAGE AND ADMINISTRATION). Pharmacokinetics Absorption Absorption of orally administered T4 from the gastrointestinal (GI) tract ranges from 40% to 80%. The majority of the levothyroxine dose is absorbed from the jejunum and upper ileum. The relative bioavailability of SYNTHROID tablets, compared to an equal nominal dose of oral levothyroxine sodium solution, is approximately 93%. T4 absorption is increased by fasting, and decreased in malabsorption syndromes and by certain foods such as soybean infant formula. Dietary fiber decreases bioavailability of T4. Absorption may also decrease with age. In addition, many drugs and foods affect T4 absorption (see DRUG INTERACTIONS and Drug-Food Interactions). Distribution Circulating thyroid hormones are greater than 99% bound to plasma proteins, including thyroxinebinding globulin (TBG), thyroxine-binding prealbumin (TBPA), and albumin (TBA), whose capacities and affinities vary for each hormone. The higher affinity of both TBG and TBPA for T4 partially explains the higher serum levels, slower metabolic clearance, and longer half-life of T4 compared to T3. Protein-bound thyroid hormones exist in reverse equilibrium with small amounts of free hormone. Only unbound hormone is metabolically active. Many drugs and physiologic conditions affect the binding of thyroid hormones to serum proteins (see DRUG INTERACTIONS and Drug-Laboratory Test Interactions). Thyroid hormones do not readily cross the placental barrier (see PRECAUTIONS - Pregnancy). Metabolism T4 is slowly eliminated (see Table 1). The major pathway of thyroid hormone metabolism is through sequential deiodination. Approximately eighty-percent of circulating T3 is derived from peripheral T4 by monodeiodination. The liver is the major site of degradation for both T4 and T3 , with T4 deiodination also occurring at a number of additional sites, including the kidney and other tissues. Approximately 80% of the daily dose of T4 is deiodinated to yield equal amounts of T3 and reverse T3 (rT3). T3 and rT3 are further deiodinated to diiodothyronine. Thyroid hormones are also metabolized via conjugation with glucuronides and sulfates and excreted directly into the bile and gut where they undergo enterohepatic recirculation. Elimination Thyroid hormones are primarily eliminated by the kidneys. A portion of the conjugated hormone reaches the colon unchanged and is eliminated in the feces. Approximately 20% of T4 is eliminated in the stool. Urinary excretion of T4 decreases with age. Table 1. Pharmacokinetic Parameters of Thyroid Hormones in Euthyroid Patients Hormone Ratio in Thyroglobulin Biologic Potency t1/2(days) Protein Binding (%)2 Levothyroxine (T4) 10 - 20 1 6-7 99.96 Liothyronine (T3) 1 4 ≤ 2 99.5 1 3 to 4 days in hyperthyroidism, 9 to 10 days in hypothyroidism 2 Includes TBG, TBPA, and TBA

CLINICAL PHARMACOLOGY Thyroid hormone synthesis and secretion is regulated by the hypothalamic-pituitary-thyroid axis. Thyrotropin-releasing hormone (TRH) released from the hypothalamus stimulates secretion of thyroidstimulating hormone, TSH, from the anterior pituitary. TSH, in turn, is the physiologic stimulus for the synthesis and secretion of thyroid hormones, L-thyroxine (T4) and L-triiodothyronine (T3), by the thyroid gland. Circulating serum T3 and T4 levels exert a feedback effect on both TRH and TSH secretion. When serum T3 and T4 levels increase, TRH and TSH secretion decrease. When thyroid hormone levels decrease, TRH and TSH secretion increase. The mechanisms by which thyroid hormones exert their physiologic actions are not completely understood, but it is thought that their principal effects are exerted through control of DNA transcription and protein synthesis. T3 and T4 diffuse into the cell nucleus and bind to thyroid receptor proteins attached to DNA. This hormone nuclear receptor complex activates gene transcription and synthesis of messenger RNA and cytoplasmic proteins. Thyroid hormones regulate multiple metabolic processes and play an essential role in normal growth and development, and normal maturation of the central nervous system and bone. The metabolic actions of thyroid hormones include augmentation of cellular respiration and thermogenesis, as well as metabolism of proteins, carbohydrates and lipids. The protein anabolic effects of thyroid hormones are essential to normal growth and development. The physiologic actions of thyroid hormones are produced predominately by T3, the majority of which (approximately 80%) is derived from T4 by deiodination in peripheral tissues. Levothyroxine, at doses individualized according to patient response, is effective as replacement or supplemental therapy in hypothyroidism of any etiology, except transient hypothyroidism during the recovery phase of subacute thyroiditis. Levothyroxine is also effective in the suppression of pituitary TSH secretion in the treatment or prevention of various types of euthyroid goiters, including thyroid nodules, Hashimoto's thyroiditis, multinodular goiter and, as adjunctive therapy in the management of thyrotropin-dependent welldifferentiated thyroid cancer (see INDICATIONS AND USAGE, PRECAUTIONS, DOSAGE AND ADMINISTRATION). Pharmacokinetics Absorption Absorption of orally administered T4 from the gastrointestinal (GI) tract ranges from 40% to 80%. The majority of the levothyroxine dose is absorbed from the jejunum and upper ileum. The relative bioavailability of LEVOXYL tablets, compared to an equal nominal dose of oral levothyroxine sodium solution, is approximately 98%. T4 absorption is increased by fasting, and decreased in malabsorption syndromes and by certain foods such as soybean infant formula. Dietary fiber decreases bioavailability of T4. Absorption may also decrease with age. In addition, many drugs and foods affect T4 absorption (see PRECAUTIONS, DRUG INTERACTIONS and Drug-Food Interactions). Distribution Circulating thyroid hormones are greater than 99% bound to plasma proteins, including thyroxinebinding globulin (TBG), thyroxine-binding prealbumin (TBPA), and albumin (TBA), whose capacities and affinities vary for each hormone. The higher affinity of both TBG and TBPA for T4 partially explains the higher serum levels, slower metabolic clearance, and longer half-life of T4 compared to T3. Protein-bound thyroid hormones exist in reverse equilibrium with small amounts of free hormone. Only unbound hormone is metabolically active. Many drugs and physiologic conditions affect the binding of thyroid hormones to serum proteins (see PRECAUTIONS, DRUG INTERACTIONS and Drug- Laboratory Test Interactions). Thyroid hormones do not readily cross the placental barrier (see PRECAUTIONS, Pregnancy). Metabolism T4 is slowly eliminated (see TABLE 1). The major pathway of thyroid hormone metabolism is through sequential deiodination. Approximately eighty-percent of circulating T3 is derived from peripheral T4 by monodeiodination. The liver is the major site of degradation for both T4 and T3, with T4 deiodination also occurring at a number of additional sites, including the kidney and other tissues. Approximately 80% of the daily dose of T is deiodinated to yield equal amounts of T and reverse T (rT3). T3 and rT3 are further deiodinated to diiodothyronine. Thyroid hormones are also metabolized via conjugation with glucuronides and sulfates and excreted directly into the bile and gut where they undergo enterohepatic recirculation. Elimination Thyroid hormones are primarily eliminated by the kidneys. A portion of the conjugated hormone reaches the colon unchanged and is eliminated in the feces. Approximately 20% of T4 is eliminated in the stool. Urinary excretion of T4 decreases with age. Table 1: Pharmacokinetic Parameters of Thyroid Hormones in Euthyroid Patients Hormone Ratio in Thyroglobulin Biologic Potency t1/2(days) Protein Binding (%)* Levothyroxine (T4) 10 - 20 1 6 - 7† 99.96 Liothyronine (T3) 1 4 ≤ 2 99.5 *Includes TBG, TBPA, and TBA †3 to 4 days in hyperthyroidism, 9 to 10 days in hypothyroidism;

CLINICAL PHARMACOLOGY Mechanism Of Action Thyroid hormones exert their physiologic actions through control of DNA transcription and protein synthesis. Triiodothyronine (T3) and levothyroxine (T4) diffuse into the cell nucleus and bind to thyroid receptor proteins attached to DNA. This hormone nuclear receptor complex activates gene transcription and synthesis of messenger RNA and cytoplasmic proteins. The physiological actions of thyroid hormones are produced predominantly by T , the majority of which (approximately 80%) is derived from T by deiodination in peripheral tissues. Pharmacodynamics Thyroid hormone synthesis and secretion is regulated by the hypothalamic pituitary-thyroid axis. Thyrotropin releasing hormone (TRH) released from the hypothalamus stimulates secretion of thyrotropin stimulating hormone (TSH) from the anterior pituitary. TSH, in turn, is the physiologic stimulus for the synthesis and secretion of thyroid hormones, T4 and T3, by the thyroid gland. Circulating serum T3 and T4 levels exert a feedback effect on both TRH and TSH secretion. When serum T3 and T4 levels increase, TRH and TSH secretion decrease. When thyroid hormone levels decrease, TRH and TSH secretion increases. TSH is used for the diagnosis of hypothyroidism and evaluation of levothyroxine therapy adequacy with other laboratory and clinical data [see Dosage]. There are drugs known to affect thyroid hormones and TSH by various mechanisms and those examples are diazepam, ethioamide, lovastatin, metoclopramide, 6-mercaptopurine, nitroprusside, perphenazine, and thiazide diuretics. Some drugs may cause a transient decrease in TSH secretion without hypothyroidism and those drugs (dose) are dopamine (greater than 1 mcg per kg per min), glucocorticoids (hydrocortisone greater than 100 mg per day or equivalent) and octreotide (greater than 100 mcg per day). Thyroid hormones regulate multiple metabolic processes and play an essential role in normal growth and development, and normal maturation of the central nervous system and bone. The metabolic actions of thyroid hormones include augmentation of cellular respiration and thermogenesis, as well as metabolism of proteins, carbohydrates and lipids. The protein anabolic effects of thyroid hormones are essential to normal growth and development. Pharmacokinetics Absorption Levothyroxine Sodium for Injection is administered via the intravenous route. Following administration, the synthetic levothyroxine cannot be distinguished from the natural hormone that is secreted endogenously. Distribution Circulating thyroid hormones are greater than 99% bound to plasma proteins, including thyroxine binding globulin (TBG), thyroxine binding prealbumin (TBPA), and albumin (TBA), whose capacities and affinities vary for each hormone. The higher affinity of both TBG and TBPA for T4 partially explains the higher serum levels, slower metabolic clearance, and longer half life of T4 compared to T3. Protein bound thyroid hormones exist in reverse equilibrium with small amounts of free hormone. Only unbound hormone is metabolically active. Many drugs and physiologic conditions affect the binding of thyroid hormones to serum proteins [see WARNINGS AND PRECAUTIONS and DRUG INTERACTIONS]. Thyroid hormones do not readily cross the placental barrier [see WARNINGS AND PRECAUTIONS and Use in Specific Populations]. Metabolism T4 is slowly eliminated. The major pathway of thyroid hormone metabolism is through sequential deiodination. Approximately eighty percent of circulating T3 is derived from peripheral T4 by monodeiodination. The liver is the major site of degradation for both T4 and T3, with T4 deiodination also occurring at a number of additional sites, including the kidney and other tissues. Approximately 80% of the daily dose of T4 is deiodinated to yield equal amounts of T3 and reverse T4 (r T3). T3 and r T3 are further deiodinated to diiodothyronine. Thyroid hormones are also metabolized via conjugation with glucuronides and sulfates and excreted directly into the bile and gut where they undergo enterohepatic recirculation. Elimination Thyroid hormones are primarily eliminated by the kidneys. A portion of the conjugated hormone reaches the colon unchanged, where it is hydrolyzed and eliminated in feces as the free hormones. Urinary excretion of T4 decreases with age. Table 1: Pharmacokinetic Parameters of Thyroid Hormones in Euthyroid Patients Hormone Ratio in Thyroglobulin Biologic Potency Half-Life (Days) Protein Binding (%)2 T4 10 to 20 1 6 to 81 99.96 T3 1 4 < 2 99.5 T4 : Levothyroxine T3: Liothyronine 13 to 4 days in hyperthyroidism, 9 to 10 days in hypothyroidism. 2Includes TBG, TBPA, and TBA. Drug Interactions A listing of drug interaction with T4 is provided in the following tables, although it may not be comprehensive due to the introduction of new drugs that interact with the thyroidal axis or the discovery of previously unknown interactions. The prescriber should be aware of this fact and should consult appropriate reference sources (e.g., package inserts of newly approved drugs, medical literature) for additional information if a drug-drug interaction with levothyroxine is suspected. Table 2: Drugs That May Alter T4 and T3 Serum Transport Without Affecting free T4 Concentration (Euthyroidism) Drugs That May Increase Serum TBG Concentration Drugs That May Decrease Serum TBG Concentration Clofibrate Estrogen-containing oral contraceptives Estrogens (oral) Heroin/Methadone 5-Fluorouracil Mitotane Tamoxifen Androgens/Anabolic Steroids Asparaginase Glucocorticoids Slow-Release Nicotinic Acid Drugs That May Cause Protein-Binding Site Displacement Potential impact: Administration of these agents with levothyroxine results in an initial transient increase in FT4. Continued administration results in a decrease in serum T4 and normal FT4 and TSH concentrations and, therefore, patients are clinically euthyroid. Salicylates ( > 2 g/day) Salicylates inhibit binding of T4 and T3 to TBG and transthyretin. An initial increase in serum FT4 is followed by return of FT4 to normal levels with sustained therapeutic serum salicylate concentrations, although total-T4 levels may decrease by as much as 30%. Other drugs: Furosemide ( > 80 mg IV) Heparin Hydantoins Non-Steroidal Anti-inflammatory Drugs Fenamates Phenylbutazone Table 3: Drugs That May Alter Hepatic Metabolism of T4 (Hypothyroidism) Potential impact: Stimulation of hepatic microsomal drug-metabolizing enzyme activity may cause increased hepatic degradation of levothyroxine, resulting in increased levothyroxine requirements. Drug or Drug Class Carbamazepine Hydantoins Phenytoin and carbamazepine reduce serum protein binding of levothyroxine, and total- and free- T4 may be reduced by 20% to 40%, but most patients have normal serum TSH levels and are clinically euthyroid. Other drugs: Phenobarbital Rifampin Table 4: Drugs That May Decrease Conversion of T4 to T3 Potential impact: Administration of these enzyme inhibitors decreases the peripheral conversion of T4 to T3, leading to decreased T3 levels. However, serum T4 levels are usually normal but may occasionally be slightly increased. Drug or Drug Class Effect Beta-adrenergic antagonists (e.g.Propranolol > 160 mg/day) In patients treated with large doses of propranolol ( > 160 mg/day), T3 and T4 levels change slightly, TSH levels remain normal, and patients are clinically euthyroid. It should be noted that actions of particular beta-adrenergic antagonists may be impaired when the hypothyroid patient is converted to the euthyroid state. Glucocorticoids (e.g. Dexamethasone ≥ 4 mg/day) Short-term administration of large doses of glucocorticoids may decrease serum T3 concentrations by 30% with minimal change in serum T4 levels. However, long-term glucocorticoid therapy may result in slightly decreased T3 and T4 levels due to decreased TBG production (see above). Other drug: Amiodarone Animal Toxicology And Pharmacology No animal toxicology studies have been conducted with Levothyroxine Sodium for Injection. Clinical Studies No clinical studies have been conducted with Levothyroxine Sodium for Injection in patients with myxedema coma. However, data from published literature support the intravenous use of levothyroxine sodium for the treatment of myxedema coma.

CLINICAL PHARMACOLOGY Thyroid hormone synthesis and secretion is regulated by the hypothalamic-pituitary-thyroid axis. Thyrotropin-releasing hormone (TRH) released from the hypothalamus stimulates secretion of thyrotropin-stimulating hormone, TSH, from the anterior pituitary. TSH, in turn, is the physiologic stimulus for the synthesis and secretion of thyroid hormones, L-thyroxine (T4) and L-triiodothyronine (T3), by the thyroid gland. Circulating serum T3 and T4 levels exert a feedback effect on both TRH and TSH secretion. When serum T3 and T4 levels increase, TRH and TSH secretion decrease. When thyroid hormone levels decrease, TRH and TSH secretion increase. The mechanisms by which thyroid hormones exert their physiologic actions are not completely understood, but it is thought that their principal effects are exerted through control of DNA transcription and protein synthesis. T3 and T4 diffuse into the cell nucleus and bind to thyroid receptor proteins attached to DNA. This hormone nuclear receptor complex activates gene transcription and synthesis of messenger RNA and cytoplasmic proteins. Thyroid hormones regulate multiple metabolic processes and play an essential role in normal growth and development, and normal maturation of the central nervous system and bone. The metabolic actions of thyroid hormones include augmentation of cellular respiration and thermogenesis, as well as metabolism of proteins, carbohydrates and lipids. The protein anabolic effects of thyroid hormones are essential to normal growth and development. The physiological actions of thyroid hormones are produced predominantly by T3, the majority of which (approximately 80%) is derived from T4 by deio-dination in peripheral tissues. Levothyroxine, at doses individualized according to patient response, is effective as replacement or supplemental therapy in hypothyroidism of any etiology, except transient hypothyroidism during the recovery phase of subacute thyroiditis. Levothyroxine is also effective in the suppression of pituitary TSH secretion in the treatment or prevention of various types of euthyroid goiters, including thyroid nodules, Hashimoto's thyroiditis, multinodular goiter and, as adjunctive therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer (see INDICATIONS AND USAGE, PRECAUTIONS, DOSAGE AND ADMINISTRATION). Pharmacokinetics Absorption Absorption of orally administered T4 from the gastrointestinal (GI) tract ranges from 40% to 80%. The majority of the levothyroxine dose is absorbed from the jejunum and upper ileum. The relative bioavailability of LEVOTHROID® (levothyroxine sodium) tablets, compared to an equal nominal dose of oral levothy-roxine sodium solution, is approximately 94%. T4 absorption is increased by fasting, and decreased in malabsorption syndromes and by certain foods such as soybean infant formula. Dietary fiber decreases bioavailability of T4. Absorption may also decrease with age. In addition, many drugs and foods affect T4 absorption (see PRECAUTIONS, DRUG INTERACTIONS and Drug-Food Interactions). Distribution Circulating thyroid hormones are greater than 99% bound to plasma proteins, including thyroxine-binding globulin (TBG), thyroxine-binding prealbumin (TBPA), and albumin (TBA), whose capacities and affinities vary for each hormone. The higher affinity of both TBG and TBPA for T4 partially explains the higher serum levels, slower metabolic clearance, and longer half-life of T4 compared to T3. Protein-bound thyroid hormones exist in reverse equilibrium with small amounts of free hormone. Only unbound hormone is metabolically active. Many drugs and physiologic conditions affect the binding of thyroid hormones to serum proteins (see PRECAUTIONS, DRUG INTERACTIONS and Drug-Laboratory Test Interactions). Thyroid hormones do not readily cross the placental barrier (see PRECAUTIONS, Pregnancy). Metabolism T4 is slowly eliminated (see Table 1). The major pathway of thyroid hormone metabolism is through sequential deiodination. Approximately eighty-percent of circulating T3 is derived from peripheral T4 by monodeiodination. The liver is the major site of degradation for both T4 and T3, with T4 deiodination also occurring at a number of additional sites, including the kidney and other tissues. Approximately 80% of the daily dose of T4 is deiodi-nated to yield equal amounts of T3 and reverse T3 (rT3). T3 and rT3 are further deiodinated to diiodothyronine. Thyroid hormones are also metabolized via conjugation with glucuronides and sulfates and excreted directly into the bile and gut where they undergo enterohepatic recirculation. Elimination Thyroid hormones are primarily eliminated by the kidneys. A portion of the conjugated hormone reaches the colon unchanged and is eliminated in the feces. Approximately 20% of T4 is eliminated in the stool. Urinary excretion of T4 decreases with age. Table 1:Pharmacokinetic Parameters of Thyroid Hormones in Euthyroid Patients Hormone Ratio in Thyroglobulin Biologic Potency t½ (days) Protein Binding (%)2 Levothyroxine (T4) 10 - 20 1 6-71 99.96 Liothyronine (T3) 1 4 ≤ 2 99.5 13 to 4 days in hyperthyroidism, 9 to 10 days in hypothyroidism; 2 Includes TBG, TBPA, and TBA

Find Lowest Prices on Unithroid® (levothyroxine sodium) tablets, USP DESCRIPTION UNITHROID® (levothyroxine sodium tablets, USP) contain synthetic crystalline L-3,3',5,5'-tetraiodothyronine sodium salt [levothyroxine (T4) sodium]. Synthetic T4 is identical to that produced in the human thyroid gland. Levothyroxine (T4) sodium has an empirical formula of C15H10I4N NaO4 • H2O, molecular weight of 798.86 g/mol (anhydrous), and structural formula as shown: Inactive Ingredients Colloidal silicon dioxide, lactose, magnesium stearate, microcrystalline cellulose, corn starch, acacia and sodium starch glycolate. The following are the coloring additives per tablet strength: Strength (mcg) Color Additive(s) 25 FD&C Yellow No. 6 Aluminum Lake 50 None 75 FD&C Red No. 40 Aluminum Lake, FD&C Blue No. 2 Aluminum Lake 88 D&C Yellow No. 10 Aluminum Lake, FD&C Yellow No. 6 Aluminum Lake, FD&C Blue No. 1 Aluminum Lake 100 D&C Yellow No. 10 Aluminum Lake, FD&C Yellow No. 6 Aluminum Lake 112 D&C Red No. 27 Aluminum Lake 125 FD&C Yellow No. 6 Aluminum Lake, FD&C Red No. 40 Aluminum Lake, FD&C Blue No. 1 Aluminum Lake 137 FD&C Blue No. 1 Aluminum Lake 150 FD&C Blue No. 2 Aluminum Lake 175 FD&C Blue No. 1 Aluminum Lake, D&C Red No. 27 Aluminum Lake 200 FD&C Red No. 40 Aluminum Lake 300 D&C Yellow No. 10 Aluminum Lake, FD&C Yellow No. 6 Aluminum Lake, FD&C Blue No. 1 Aluminum Lake

Find Lowest Prices on SYNTHROID® (levothyroxine sodium) tablets, USP WARNING Thyroid hormones, including SYNTHROID, either alone or with other therapeutic agents, should not be used for the treatment of obesity or for weight loss. In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life threatening manifes tations of toxicity, particularly when given in association with sympathomimetic amines such as those used for their anorectic effects. DESCRIPTION SYNTHROID (levothyroxine sodium tablets, USP) contain synthetic crystalline L-3,3',5,5'- tetraiodothyronine sodium salt [levothyroxine (T4 ) sodium]. Synthetic T4 is identical to that produced in the human thyroid gland. Levothyroxine (T4 ) sodium has an empirical formula of C15H10I4N NaO4 • H2O, molecular weight of 798.86 g/mol (anhydrous), and structural formula as shown: Inactive Ingredients Acacia, confectioner's sugar (contains corn starch), lactose monohydrate, magnesium stearate, povidone, and talc. The following are the color additives by tablet strength: Strength (mcg) Color additive(s ) 25 FD&C Yellow No. 6 Aluminum Lake* 50 None 75 FD&C Red No. 40 Aluminum Lake, FD&C Blue No. 2 Aluminum Lake 88 FD&C Blue No. 1 Aluminum Lake, FD&C Yellow No. 6 Aluminum Lake*, D&C Yellow No. 10 Aluminum Lake 100 D&C Yellow No. 10 Aluminum Lake, FD&C Yellow No. 6 Aluminum Lake* 112 D&C Red No. 27 & 30 Aluminum Lake 125 FD&C Yellow No. 6 Aluminum Lake*, FD&C Red No. 40 Aluminum Lake, FD&C Blue No. 1 Aluminum Lake 137 FD&C Blue No. 1 Aluminum Lake 150 FD&C Blue No. 2 Aluminum Lake 175 FD&C Blue No. 1 Aluminum Lake, D&C Red No. 27 & 30 Aluminum Lake 200 FD&C Red No. 40 Aluminum Lake 300 D&C Yellow No. 10 Aluminum Lake, FD&C Yellow No. 6 Aluminum Lake*, FD&C Blue No. 1 Aluminum Lake *Note – FD&C Yellow No. 6 is orange in color. Meets USP Dissolution Test 3

Find Lowest Prices on Levoxyl® (levothyroxine sodium) tablets, USP DESCRIPTION –LEVOXYL® (levothyroxine sodium tablets, USP) contain synthetic crystalline L-3,3',5,5'- tetraiodothyronine sodium salt [levothyroxine (T4) sodium]. Synthetic T4 is identical to that produced in the human thyroid gland. Levothyroxine (T4) sodium has an empirical formula of C15H10I4N NaO4• H2O, molecular weight of 798.86 g/mol (anhydrous), and structural formula as shown: Inactive Ingredients Microcrystalline cellulose, croscarmellose sodium, magnesium stearate, calcium sulfate dihydrate and sodium bicarbonate. The following are the coloring additives per tablet strength: Strength (mcg) Color additive(s) 25 FD&C Yellow No. 6 Aluminum Lake 50 None 75 FD&C Blue No. 1 Aluminum Lake, D&C Red No. 30 Aluminum Lake 88 FD&C Yellow No. 6 Aluminum Lake, FD&C Blue No. 1 Aluminum Lake, D&C Yellow No. 10 Aluminum Lake 100 FD&C Yellow No. 6 Aluminum Lake, D&C Yellow No. 10 Aluminum Lake 112 FD&C Yellow No. 6 Aluminum Lake, FD&C Red No. 40 Aluminum Lake, D&C Red No. 30 Aluminum Lake 125 FD&C Red No. 40 Aluminum Lake, D&C Yellow No. 10 Aluminum Lake 137 FD&C Blue No. 1 Aluminum Lake 150 FD&C Blue No. 1 Aluminum Lake, D&C Red No. 30 Aluminum Lake 175 FD&C Blue No. 1 Aluminum Lake, D&C Yellow No. 10 Aluminum Lake 200 D&C Red No. 30 Aluminum Lake, D&C Yellow No. 10 Aluminum Lake

Levothyroxine Sodium (levothyroxine sodium) Anhydrous Injection WARNING NOT FOR TREATMENT OF OBESITY OR FOR WEIGHT LOSS Thyroid hormones, including Levothyroxine Sodium for Injection, should not be used for the treatment of obesity or for weight loss. Larger doses may produce serious or even life threatening manifestations of toxicity. DESCRIPTION Levothyroxine Sodium for Injection contains synthetic crystalline levothyroxine (L-thyroxine) sodium salt. Levothyroxine sodium has an empirical formula of C15H10I4NNaO4, a molecular weight of 798.85 g/mol (anhydrous), and the following structural formula: Levothyroxine Sodium for Injection is a sterile, preservative-free lyophilized powder consisting of the active ingredient, levothyroxine sodium, and the excipients dibasic sodium phosphate heptahydrate, USP; mannitol, USP; and sodium hydroxide, NF in single-use amber glass vials. Levothyroxine Sodium for Injection is available at two dosage strengths: 100 mcg per vial and 200 mcg per vial.

LEVOTHROID® (levothyroxine sodium) Tablets, USP DESCRIPTION LEVOTHROID® (levothyroxine sodium) Tablets, USP contains synthetic crystalline L-3, 3', 5, 5'-tetraiodothyronine sodium salt [levothyroxine (T4) sodium]. Synthetic T4 is identical to that produced in the human thyroid gland. Levothyroxine (T4) sodium has an empirical formula of C15H10I4N NaO4 x H2O, molecular weight of 798. 86 g/mol (anhydrous), and structural formula as shown: Inactive Ingredients: Microcrystalline cellulose, calcium phosphate dibasic, povidone and magnesium stearate. The following are the coloring additives per tablet strength. Strength (mcg) Color additive(s) 25 FD&C Yellow No.6 Aluminum Lake 50 None 75 FD&C Blue No.2 Aluminum Lake, FD&C Red No.40 Aluminum Lake 88 FD&C Yellow No.6 Aluminum Lake, FD&C Blue No.1 Aluminum Lake, D&C Yellow No.10 Aluminum Lake 100 FD&C Yellow No.6 Aluminum Lake, D&C Yellow No.10 Aluminum Lake 112 D&C Red No.27 Aluminum Lake, D&C Red No.30 Aluminum Lake 125 FD&C Blue No.1 Aluminum Lake, FD&C Red No.40 Aluminum Lake, FD&C Yellow No.6 Aluminum Lake 137 FD&C Blue No.1 Aluminum Lake 150 FD&C Blue No.2 Aluminum Lake 175 FD&C Blue No.1 Aluminum Lake, D&C Red No.30 Aluminum Lake, D&C Red No.27 Aluminum Lake 200 FD&C Red No.40 Aluminum Lake 300 FD&C Yellow No.6 Aluminum Lake, FD&C Blue No.1 Aluminum Lake, D&C Yellow No.10 Aluminum Lake

INDICATIONS Levothyroxine sodium is used for the following indications: Hypothyroidism As replacement or supplemental therapy in congenital or acquired hypothyroidism of any etiology, except transient hypothyroidism during the recovery phase of subacute thyroiditis. Specific indications include: primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) hypothyroidism and subclinical hypothyroidism. Primary hypothyroidism may result from functional deficiency, primary atrophy, partial or total congenital absence of the thyroid gland, or from the effects of surgery, radiation, or drugs, with or without the presence of goiter. Pituitary TSH Suppression In the treatment or prevention of various types of euthyroid goiters (see WARNINGS and PRECAUTIONS), including thyroid nodules (see WARNINGS and PRECAUTIONS), subacute or chronic Iymphocytic thyroiditis (Hashimoto's thyroiditis), multinodular goiter (see WARNINGS and PRECAUTIONS), and, as an adjunct to surgery and radioiodine therapy in the management of thyrotropindependent well-differentiated thyroid cancer. DOSAGE AND ADMINISTRATION General Principles The goal of replacement therapy is to achieve and maintain a clinical and biochemical euthyroid state. The goal of suppressive therapy is to inhibit growth and/or function of abnormal thyroid tissue. The dose of UNITHROID that is adequate to achieve these goals depends on a variety of factors including the patient's age, body weight, cardiovascular status, concomitant medical conditions, including pregnancy, concomitant medications, and the specific nature of the condition being treated (see WARNINGS and PRECAUTIONS). Hence, the following recommendations serve only as dosing guidelines. Dosing must be individualized and adjustments made based on periodic assessment of the patient's clinical response and laboratory parameters (see PRECAUTIONS, Laboratory Tests). UNITHROID should be taken in the morning on an empty stomach, at least one-half hour to one hour before any food is eaten. UNITHROID should be taken at least 4 hours apart from drugs that are known to interfere with its absorption (see PRECAUTIONS: DRUG INTERACTIONS). Due to the long half-life of levothyroxine, the peak therapeutic effect at a given dose of levothyroxine sodium may not be attained for 4-6 weeks. Caution should be exercised when administering UNITHROID to patients with underlying cardiovascular disease, to the elderly, and to those with concomitant adrenal insufficiency (see PRECAUTIONS). Specific Patient Populations Hypothyroidism in Adults and in Children in Whom Growth and Puberty are Complete (see WARNINGS and PRECAUTIONS, Laboratory Tests). Therapy may begin at full replacement doses in otherwise healthy individuals less than 50 years old and in those older than 50 years who have been recently treated for hyperthyroidism or who have been hypothyroid for only a short time (such as a few months). The average full replacement dose of levothyroxine sodium is approximately 1.7 mcg/kg/day (e.g., 100-125 mcg/day for a 70 kg adult). Older patients may require less than 1 mcg/kg/day. Levothyroxine sodium doses greater than 200 mcg/day are seldom required. An inadequate response to daily doses ≥ 300 mcg/day is rare and may indicate poor compliance, malabsorption, and/or drug interactions. For most patients older than 50 years or for patients under 50 years of age with underlying cardiac disease, an initial starting dose of 25-50 mcg/day of levothyroxine sodium is recommended, with gradual increments in dose at 6-8 week intervals, as needed. The recommended starting dose of levothyroxine sodium in elderly patients with cardiac disease is 12.5-25 mcg/day, with gradual dose increments at 4-6 week intervals. The levothyroxine sodium dose is generally adjusted in 12.5-25 mcg increments until the patient with primary hypothyroidism is clinically euthyroid and the serum TSH has normalized. In patients with severe hypothyroidism, the recommended initial levothyroxine sodium dose is 12.5-25 mcg/day with increases of 25 mcg/day every 2-4 weeks, accompanied by clinical and laboratory assessment, until the TSH level is normalized. In patients with secondary (pituitary) or tertiary (hypothalamic) hypothyroidism, the levothyroxine sodium dose should be titrated until the patient is clinically euthyroid and the serum free-T4 level is restored to the upper half of the normal range. Pediatric Dosage - Congenital or Acquired Hypothyroidism (see PRECAUTIONS, Laboratory Tests) General Principles In general, levothyroxine therapy should be instituted at full replacement doses as soon as possible. Delays in diagnosis and institution of therapy may have deleterious effects on the child's intellectual and physical growth and development. Undertreatment and overtreatment should be avoided (see PRECAUTIONS, Pediatric Use). UNITHROID may be administered to infants and children who cannot swallow intact tablets by crushing the tablet and suspending the freshly crushed tablet in a small amount (5-10 mL or 1-2 teaspoons) of water. This suspension can be administered by spoon or dropper. DO NOT STORE THE SUSPENSION. Foods that decrease absorption of levothyroxine, such as soybean infant formula, should not be used for administering levothyroxine sodium tablets. (see Drug-Food Interactions). Newborns The recommended starting dose of levothyroxine sodium in newborn infants is 10-15 mcg/kg/day. A lower starting dose (e.g., 25 mcg/day) should be considered in infants at risk for cardiac failure, and the dose should be increased in 4-6 weeks as needed based on clinical and laboratory response to treatment. In infants with very low ( < 5 mcg/dL) or undetectable serum T4 concentrations, the recommended initial starting dose is 50 mcg/day of levothyroxine sodium. Infants And Children Levothyroxine therapy is usually initiated at full replacement doses, with the recommended dose per body weight decreasing with age (see TABLE 3). However, in children with chronic or severe hypothyroidism, an initial dose of 25 mcg/day of levothyroxine sodium is recommended with increments of 25 mcg every 2-4 weeks until the desired effect is achieved. Hyperactivity in an older child can be minimized if the starting dose is one-fourth of the recommended full replacement dose, and the dose is then increased on a weekly basis by an amount equal to one-fourth the full-recommended replacement dose until the full recommended replacement dose is reached. Table 3: Levothyroxine Sodium Dosing Guidelines for Pediatric Hypothyroidism AGE Daily Dose Per Kg Body Weighta 0-3 months 10-15 mcg/kg/day 3-6 months 8-10 mcg/kg/day 6-12 months 6-8 mcg/kg/day 1-5 years 5-6 mcg/kg/day 6-12 years 4-5 mcg/kg/day > 12 years but growth and puberty incomplete 2-3 mcg/kg/day Growth and puberty complete 1.7 mcg/kg/day aThe dose should be adjusted based on clinical response and laboratory parameters (see PRECAUTlONS, Laboratory Tests and Pediatric Use). Pregnancy Pregnancy may increase levothyroxine requirements (see Pregnancy). Subclinical Hypothyroidism If this condition is treated, a lower levothyroxine sodium dose (e.g., 1 mcg/kg/day) than that used for full replacement may be adequate to normalize the serum TSH level. Patients who are not treated should be monitored yearly for changes in clinical status and thyroid laboratory parameters. TSH Suppression In Well-differentiated Thyroid Cancer And Thyroid Nodules The target level for TSH suppression in these conditions has not been established with controlled studies. In addition, the efficacy of TSH suppression for benign nodular disease is controversial. Therefore, the dose of UNITHROID used for TSH suppression should be individualized based on the specific disease and the patient being treated. In the treatment of well differentiated (papillary and follicular) thyroid cancer, levothyroxine is used as an adjunct to surgery and radioiodine therapy. Generally, TSH is suppressed to < 0.1 mU/L, and this usually requires a levothyroxine sodium dose of greater than 2 mcg/kg/day. However, in patients with high-risk tumors, the target level for TSH suppression may be < 0.01 mU/L. In the treatment of benign nodules and nontoxic multinodular goiter, TSH is generally suppressed to a higher target (e.g., 0.1-0.5 mU/L for nodules and 0.5-1.0 mU/L for multinodular goiter) than that used for the treatment of thyroid cancer. Levothyroxine sodium is contraindicated if the serum TSH is already suppressed due to the risk of precipitating overt thyrotoxicosis (see CONTRAINDICATIONS, WARNINGS and PRECAUTIONS). Myxedema Coma Myxedema coma is a life-threatening emergency characterized by poor circulation and hypometabolism, and may result in unpredictable absorption of levothyroxine sodium from the gastrointestinal tract. Therefore, oral thyroid hormone drug products are not recommended to treat this condition. Thyroid hormone products formulated for intravenous administration should be administered. HOW SUPPLIED UNITHROID® (levothyroxine sodium tablets, USP) are round, color coded, partial bisected tablets debossed with JSP and ID Number: Strength (mcg) Color NDC# for bottles of 100 25 Peach NDC 60846-801-01 50 White NDC 60846-802-01 75 Purple NDC 60846-803-01 88 Olive NDC 60846-804-01 100 Yellow NDC 60846-805-01 112 Rose NDC 60846-806-01 125 Tan NDC 60846-807-01 137 Blue NDC 60846-808-01 150 Lt. Blue NDC 60846-809-01 175 Lilac NDC 60846-810-01 200 Pink NDC 60846-811-01 300 Green NDC 60846-812-01 Storage Conditions 20°C to 25°C (68°F to 77°F) with excursions between 15°C to 30°C (59°F to 86° F) Manufactured by: Jerome Stevens Pharmaceuticals, Inc., Bohemia, NY 11716. Distributed by: Gemini Laboratories, Bridgewater, NJ 08807. Revised: Apr 2014

INDICATIONS Levothyroxine sodium is used for the following indications: Hypothyroidism As replacement or supplemental therapy in congenital or acquired hypothyroidism of any etiology, except transient hypothyroidism during the recovery phase of subacute thyroiditis. Specific indications include: primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) hypothyroidism and subclinical hypothyroidism. Primary hypothyroidism may result from functional deficiency, primary atrophy, partial or total congenital absence of the thyroid gland, or from the effects of surgery, radiation, or drugs, with or without the presence of goiter. Pituitary TSH Suppression In the treatment or prevention of various types of euthyroid goiters (see WARNINGS and PRECAUTIONS), including thyroid nodules (see WARNINGS and PRECAUTIONS), subacute or chronic lymphocytic thyroiditis (Hashimoto's thyroiditis), multinodular goiter (see WARNINGS and PRECAUTIONS) and, as an adjunct to surgery and radioiodine therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer. DOSAGE AND ADMINISTRATION General Principles The goal of replacement therapy is to achieve and maintain a clinical and biochemical euthyroid state. The goal of suppressive therapy is to inhibit growth and/or function of abnormal thyroid tissue. The dose of SYNTHROID that is adequate to achieve these goals depends on a variety of factors including the patient's age, body weight, cardiovascular status, concomitant medical conditions, including pregnancy, concomitant medications, and the specific nature of the condition being treated (see WARNINGS and PRECAUTIONS). Hence, the following recommendations serve only as dosing guidelines. Dosing must be individualized and adjustments made based on periodic assessment of the patient's clinical response and laboratory parameters (see PRECAUTIONS - Laboratory Tests). SYNTHROID is administered as a single daily dose, preferably one-half to one-hour before breakfast. SYNTHROID should be taken at least 4 hours apart from drugs that are known to interfere with its absorption (see DRUG INTERACTIONS). Due to the long half-life of levothyroxine, the peak therapeutic effect at a given dose of levothyroxine sodium may not be attained for 4-6 weeks. Caution should be exercised when administering SYNTHROID to patients with underlying cardiovascular disease, to the elderly, and to those with concomitant adrenal insufficiency (see PRECAUTIONS). Specific Patient Populations Hypothyroidism in Adults and in Children in Whom Growth and Puberty are Complete (see WARNINGS and PRECAUTIONS - Laboratory Tests) Therapy may begin at full replacement doses in otherwise healthy individuals less than 50 years old and in those older than 50 years who have been recently treated for hyperthyroidism or who have been hypothyroid for only a short time (such as a few months). The average full replacement dose of levothyroxine sodium is approximately 1.7 mcg/kg/day (e.g., 100-125 mcg/day for a 70 kg adult). Older patients may require less than 1 mcg/kg/day. Levothyroxine sodium doses greater than 200 mcg/day are seldom required. An inadequate response to daily doses ≥ 300 mcg/day is rare and may indicate poor compliance, malabsorption, and/or drug interactions. For most patients older than 50 years or for patients under 50 years of age with underlying cardiac disease, an initial starting dose of 25-50 mcg/day of levothyroxine sodium is recommended, with gradual increments in dose at 6-8 week intervals, as needed. The recommended starting dose of levothyroxine sodium in elderly patients with cardiac disease is 12.5-25 mcg/day , with gradual dose increments at 4-6 week intervals. The levothyroxine sodium dose is generally adjusted in 12.5-25 mcg increments until the patient with primary hypothyroidism is clinically euthyroid and the serum TSH has normalized. In patients with severe hypothyroidism, the recommended initial levothyroxine sodium dose is 12.5-25 mcg/day with increases of 25 mcg/day every 2-4 weeks, accompanied by clinical and laboratory assessment, until the TSH level is normalized. In patients with secondary (pituitary) or tertiary (hypothalamic) hypothyroidism, the levothyroxine sodium dose should be titrated until the patient is clinically euthyroid and the serum free- T4 level is restored to the upper half of the normal range. Pediatric Dosage - Congenital Or Acquired Hypothyroidism (see PRECAUTIONS - Laboratory Tests) General Principles In general, levothyroxine therapy should be instituted at full replacement doses as soon as possible. Delays in diagnosis and institution of therapy may have deleterious effects on the child's intellectual and physical growth and development. Undertreatment and overtreatment should be avoided (see PRECAUTIONS - Pediatric Use). SYNTHROID may be administered to infants and children who cannot swallow intact tablets by crushing the tablet and suspending the freshly crushed tablet in a small amount (5-10 mL or 1-2 teaspoons) of water. This suspension can be administered by spoon or by dropper. DO NOT STORE THE SUSPENSION. Foods that decrease absorption of levothyroxine, such as soybean infant formula, should not be used for administering levothyroxine sodium tablets (see PRECAUTIONS - Drug-Food Interactions). Newborns The recommended starting dose of levothyroxine sodium in newborn infants is 10-15 mcg/kg/day . A lower starting dose (e.g., 25 mcg/day) should be considered in infants at risk for cardiac failure, and the dose should be increased in 4-6 weeks as needed based on clinical and laboratory response to treatment. In infants with very low (< 5 mcg/dL) or undetectable serum T4 concentrations, the recommended initial starting dose is 50 mcg/day of levothyroxine sodium. Infants and Children Levothyroxine therapy is usually initiated at full replacement doses, with the recommended dose per body weight decreasing with age (see Table 3). However, in children with chronic or severe hypothyroidism, an initial dose of 25 mcg/day of levothyroxine sodium is recommended with increments of 25 mcg every 2-4 weeks until the desired effect is achieved. Hyperactivity in an older child can be minimized if the starting dose is one-fourth of the recommended full replacement dose, and the dose is then increased on a weekly basis by an amount equal to one-fourth the full-recommended replacement dose until the full recommended replacement dose is reached. Table 3. Levothyroxine Sodium Dosing Guidelines for Pediatric Hypothyroidism AGE Daily Dose Per Kg Body Weighta 0-3 months 10-15 mcg/kg/day 3-6 months 8-10 mcg/kg/day 6-12 months 6-8 mcg/kg/day 1-5 years 5-6 mcg/kg/day 6-12 years 4-5 mcg/kg/day > 12 years but growth and puberty incomplete 2-3 mcg/kg/day Growth and puberty complete 1.7 mcg/kg/day a The dose should be adjusted based on clinical response and laboratory parameters (see PRECAUTIONS - Laboratory Tests and Pediatric Use). Pregnancy Pregnancy may increase levothyroxine requirements (see PREGNANCY). Subclinical Hypothyroidism If this condition is treated, a lower levothyroxine sodium dose (e.g., 1 mcg/kg/day) than that used for full replacement may be adequate to normalize the serum TSH level. Patients who are not treated should be monitored yearly for changes in clinical status and thyroid laboratory parameters. TSH Suppression In Well-Differentiated Thyroid Cancer And Thyroid Nodules The target level for TSH suppression in these conditions has not been established with controlled studies. In addition, the efficacy of TSH suppression for benign nodular disease is controversial. Therefore, the dose of SYNTHROID used for TSH suppression should be individualized based on the specific disease and the patient being treated. In the treatment of well-differentiated (papillary and follicular) thyroid cancer, levothyroxine is used as an adjunct to surgery and radioiodine therapy. Generally, TSH is suppressed to < 0.1 mU/L, and this usually requires a levothyroxine sodium dose of greater than 2 mcg/kg/day. However, in patients with high-risk tumors, the target level for TSH suppression may be < 0.01 mU/L. In the treatment of benign nodules and nontoxic multinodular goiter, TSH is generally suppressed to a higher target (e.g., 0.1 to either 0.5 or 1.0 mU/L) than that used for the treatment of thyroid cancer. Levothyroxine sodium is contraindicated if the serum TSH is already suppressed due to the risk of precipitating overt thyrotoxicosis (see CONTRAINDICATIONS, WARNINGS and PRECAUTIONS). Myxedema Coma Myxedema coma is a life-threatening emergency characterized by poor circulation and hypometabolism, and may result in unpredictable absorption of levothyroxine sodium from the gastrointestinal tract. Therefore, oral thyroid hormone drug products are not recommended to treat this condition. Thyroid hormone products formulated for intravenous administration should be administered. HOW SUPPLIED SYNTHROID (levothyroxine s odium tablets , USP) are round, color coded, scored and debossed with "SYNTHROID" on one side and potency on the other side. They are supplied as follows: Strength (mcg) Color NDC# for bottles of 90 NDC # for bottles of 100 NDC # for bottles of 1000 NDC # for unit dose cartons of 100 25 orange 0074-4341- 90 0074-4341-13 0074-4341-19 - 50 white 0074-4552- 90 0074-4552-13 0074-4552-19 0074-4552- 11 75 violet 0074-5182- 90 0074-5182-13 0074-5182-19 0074-5182- 11 88 olive 0074- 6594-90 0074-6594-13 0074-6594-19 - 100 yellow 0074- 6624-90 0074-6624-13 0074-6624-19 0074-6624- 11 112 rose 0074- 9296-90 0074-9296-13 0074-9296-19 - 125 brown 0074- 7068-90 0074-7068-13 0074-7068-19 0074-7068- 11 137 turquoise 0074-3727- 90 0074-3727-13 0074-3727-19 - 150 blue 0074- 7069-90 0074-7069-13 0074-7069-19 0074-7069- 11 175 lilac 0074-7070- 90 0074-7070-13 0074-7070-19 - 200 pink 0074-7148- 90 0074-7148-13 0074-7148-19 0074-7148- 11 300 green green 0074-7149- 90 0074-7149-13 0074-7149-19 - Storage Conditions Store at 25°C (77°F); excursions permitted to 15°-30°C (59°-86°F) [see USP Controlled Room Temperature]. SYNTHROID tablets should be protected from light and moisture. Manufactured by: AbbVie Inc. North Chicago, IL 60064, U.S.A. 03-A663. Revised: June 2016

INDICATIONS Levothyroxine sodium is used for the following indications: Hypothyroidism As replacement or supplemental therapy in congenital or acquired hypothyroidism of any etiology, except transient hypothyroidism during the recovery phase of subacute thyroiditis. Specific indications include: primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) hypothyroidism and subclinical hypothyroidism. Primary hypothyroidism may result from functional deficiency, primary atrophy, partial or total congenital absence of the thyroid gland, or from the effects of surgery, radiation, or drugs, with or without the presence of goiter. Pituitary TSH Suppression In the treatment or prevention of various types of euthyroid goiters (see WARNINGS and PRECAUTIONS), including thyroid nodules (see WARNINGS and PRECAUTIONS), subacute or chronic lymphocytic thyroiditis (Hashimoto's thyroiditis), multinodular goiter (see WARNINGS and PRECAUTIONS) and, as an adjunct to surgery and radioiodine therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer. DOSAGE AND ADMINISTRATION General Principles The goal of replacement therapy is to achieve and maintain a clinical and biochemical euthyroid state. The goal of suppressive therapy is to inhibit growth and/or function of abnormal thyroid tissue. The dose of LEVOXYL that is adequate to achieve these goals depends on a variety of factors including the patient's age, body weight, cardiovascular status, concomitant medical conditions, including pregnancy, concomitant medications, and the specific nature of the condition being treated (see WARNINGS and PRECAUTIONS). Hence, the following recommendations serve only as dosing guidelines. Dosing must be individualized and adjustments made based on periodic assessment of the patient's clinical response and laboratory parameters (see PRECAUTIONS, Laboratory Tests). The LEVOXYL should be taken in the morning on an empty stomach, at least one-half hour before any food is eaten. LEVOXYL should be taken at least 4 hours apart from drugs that are known to interfere with its absorption (see PRECAUTIONS , DRUG INTERACTIONS ). LEVOXYL should be taken with water (see PATIENT INFORMATION and ADVERSE REACTIONS). Due to the long half-life of levothyroxine, the peak therapeutic effect at a given dose of levothyroxine sodium may not be attained for 4 - 6 weeks. Caution should be exercised when administering LEVOXYL to patients with underlying cardiovascular disease, to the elderly, and to those with concomitant adrenal insufficiency (see PRECAUTIONS). Specific Patient Populations Hypothyroidism in Adults and in Children in Whom Growth and Puberty are Complete (see WARNINGS and PRECAUTIONS, Laboratory Tests) Therapy may begin at full replacement doses in otherwise healthy individuals less than 50 years old and in those older than 50 years who have been recently treated for hyperthyroidism or who have been hypothyroid for only a short time (such as a few months). The average full replacement dose of levothyroxine sodium is approximately 1.7 mcg/kg/day (e.g., 100 - 125 mcg/day for a 70 kg adult). Older patients may require less than 1 mcg/kg/day. Levothyroxine sodium doses greater than 200 mcg/day are seldom required. An inadequate response to daily doses ≥300 mcg/day is rare and may indicate poor compliance, malabsorption, and/or drug interactions. For most patients older than 50 years or for patients under 50 years of age with underlying cardiac disease, an initial starting dose of 25 - 50 mcg/day of levothyroxine sodium is recommended, with gradual increments in dose at 6 - 8 week intervals, as needed. The recommended starting dose of levothyroxine sodium in elderly patients with cardiac disease is 12.5 - 25 mcg/day, with gradual dose increments at 4 - 6 week intervals. The levothyroxine sodium dose is generally adjusted in 12.5 - 25 mcg increments until the patient with primary hypothyroidism is clinically euthyroid and the serum TSH has normalized. In patients with severe hypothyroidism, the recommended initial levothyroxine sodium dose is 12.5 - 25 mcg/day with increases of 25 mcg/day every 2 - 4 weeks, accompanied by clinical and laboratory assessment, until the TSH level is normalized. In patients with secondary (pituitary) or tertiary (hypothalamic) hypothyroidism, the levothyroxine sodium dose should be titrated until the patient is clinically euthyroid and the serum free-T level is restored to the upper half of the normal range. Pediatric Dosage - Congenital Or Acquired Hypothyroidism (see PRECAUTIONS, Laboratory Tests) General Principles In general, levothyroxine therapy should be instituted at full replacement doses as soon as possible. Delays in diagnosis and institution of therapy may have deleterious effects on the child's intellectual and physical growth and development. Undertreatment and overtreatment should be avoided (see PRECAUTIONS, Pediatric Use). LEVOXYL may be administered to infants and children who cannot swallow intact tablets by crushing the tablet and suspending the freshly crushed tablet in a small amount (5 - 10 mL or 1 - 2 teaspoons) of water. This suspension can be administered by spoon or dropper. DO NOT STORE THE SUSPENSION. Foods that decrease absorption of levothyroxine, such as soybean infant formula, should not be used for administering levothyroxine sodium tablets. (see PRECAUTIONS, Drug- Food Interactions). Newborns The recommended starting dose of levothyroxine sodium in newborn infants is 10 - 15 mcg/kg/day. A lower starting dose (e.g., 25 mcg/day) should be considered in infants at risk for cardiac failure, and the dose should be increased in 4 - 6 weeks as needed based on clinical and laboratory response to treatment. In infants with very low (< 5 mcg/dL) or undetectable serum T concentrations, the recommended initial starting dose is 50 mcg/day of levothyroxine sodium. Infants and Children Levothyroxine therapy is usually initiated at full replacement doses, with the recommended dose per body weight decreasing with age (see TABLE 3). However, in children with chronic or severe hypothyroidism, an initial dose of 25 mcg/day of levothyroxine sodium is recommended with increments of 25 mcg every 2 - 4 weeks until the desired effect is achieved. Hyperactivity in an older child can be minimized if the starting dose is one-fourth of the recommended full replacement dose, and the dose is then increased on a weekly basis by an amount equal to one-fourth the full recommended replacement dose until the full recommended replacement dose is reached. Table 3: Levothyroxine Sodium Dosing Guidelines for Pediatric Hypothyroidism AGE Daily Dose Per Kg Body Weight* 0 - 3 months 10 - 15 mcg/kg/day 3 - 6 months 8 - 10 mcg/kg/day 6 - 12 months 6 - 8 mcg/kg/day 1 - 5 years 5 - 6 mcg/kg/day 6 - 12 years 4 - 5 mcg/kg/day >12 years 2 - 3 mcg/kg/day Growth and puberty complete 1.7 mcg/kg/day *The dose should be adjusted based on clinical response and laboratory parameters (see PRECAUTIONS, Laboratory Tests and Pediatric Use). Pregnancy Pregnancy may increase levothyroxine requirements (see Pregnancy). Subclinical Hypothyroidism If this condition is treated, a lower levothyroxine sodium dose (e.g., 1 mcg/kg/day) than that used for full replacement may be adequate to normalize the serum TSH level. Patients who are not treated should be monitored yearly for changes in clinical status and thyroid laboratory parameters. TSH Suppression In Well-Differentiated Thyroid Cancer And Thyroid Nodules The target level for TSH suppression in these conditions has not been established with controlled studies. In addition, the efficacy of TSH suppression for benign nodular disease is controversial. Therefore, the dose of LEVOXYL used for TSH suppression should be individualized based on the specific disease and the patient being treated. In the treatment of well differentiated (papillary and follicular) thyroid cancer, levothyroxine is used as an adjunct to surgery and radioiodine therapy. Generally, TSH is suppressed to <0.1 mU/L, and this usually requires a levothyroxine sodium dose of greater than 2 mcg/kg/day. However, in patients with high-risk tumors, the target level for TSH suppression may be <0.01 mU/L. In the treatment of benign nodules and nontoxic multinodular goiter, TSH is generally suppressed to a higher target (e.g., 0.1 - 0.5 mU/L for nodules and 0.5 - 1.0 mU/L for multinodular goiter) than that used for the treatment of thyroid cancer. Levothyroxine sodium is contraindicated if the serum TSH is already suppressed due to the risk of precipitating overt thyrotoxicosis (see CONTRAINDICATIONS, WARNINGS and PRECAUTIONS). Myxedema Coma Myxedema coma is a life-threatening emergency characterized by poor circulation and hypometabolism, and may result in unpredictable absorption of levothyroxine sodium from the gastrointestinal tract. Therefore, oral thyroid hormone drug products are not recommended to treat this condition. Thyroid hormone products formulated for intravenous administration should be administered. HOW SUPPLIED LEVOXYL (levothyroxine sodium tablets, USP) are supplied as oval, color-coded, potency marked tablets in 11 strengths: Strength (mcg) Color NDC # for bottles of 100 NDC # for bottles of 1000 25 Orange NDC 60793-850-01 NDC 60793-850-10 50 White NDC 60793-851-01 NDC 60793-851-10 75 Purple NDC 60793-852-01 NDC 60793-852-10 88 Olive NDC 60793-853-01 NDC 60793-853-10 100 Yellow NDC 60793-854-01 NDC 60793-854-10 112 Rose NDC 60793-855-01 NDC 60793-855-10 125 Light Brown NDC 60793-856-01 NDC 60793-856-10 137 Dark Blue NDC 60793-857-01 NDC 60793-857-10 150 Blue NDC 60793-858-01 NDC 60793-858-10 175 Turquoise NDC 60793-859-01 NDC 60793-859-10 200 Pink NDC 60793-860-01 NDC 60793-860-10 Storage Conditions 20° - 25°C (68° - 77°F) with excursions permitted between 15° - 30°C (59° - 86°F). Meets USP Dissolution Tests 1 and 2. Distributed by: Pfizer Inc, New York, NY 10017. Revised: Sep 2014

INDICATIONS Levothyroxine Sodium for Injection is indicated for the treatment of myxedema coma. Important Limitations Of Use The relative bioavailability between Levothyroxine Sodium for Injection and oral levothyroxine products has not been established. Caution should be used when switching patients from oral levothyroxine products to Levothyroxine Sodium for Injection as accurate dosing conversion has not been studied. DOSAGE AND ADMINISTRATION Dosage An initial intravenous loading dose of Levothyroxine Sodium for Injection between 300 to 500 mcg, followed by once daily intravenous maintenance doses between 50 and 100 mcg, should be administered, as clinically indicated, until the patient can tolerate oral therapy. The age, general physical condition, cardiac risk factors, and clinical severity of myxedema and duration of myxedema symptoms should be considered when determining the starting and maintenance dosages of Levothyroxine Sodium for Injection. Levothyroxine Sodium for Injection produces a gradual increase in the circulating concentrations of the hormone with an approximate half-life of 9 to 10 days in hypothyroid patients. Daily administration of Levothyroxine Sodium for Injection should be maintained until the patient is capable of tolerating an oral dose and is clinically stable. For chronic treatment of hypothyroidism, an oral dosage form of levothyroxine should be used to maintain a euthyroid state. Relative bioavailability between Levothyroxine Sodium for Injection and oral levothyroxine products has not been established. Based on medical practice, the relative bioavailability between oral and intravenous administration of Levothyroxine Sodium for Injection is estimated to be from 48 to 74%. Due to differences in absorption characteristics of patients and the oral levothyroxine product formulations, TSH and thyroid hormone levels should be measured a few weeks after initiating oral levothyroxine and dose adjusted accordingly. Dosing In The Elderly And In Patients With Cardiovascular Disease Intravenous levothyroxine may be associated with cardiac toxicity–including arrhythmias, tachycardia, myocardial ischemia and infarction, or worsening of congestive heart failure and death–in the elderly and in those with underlying cardiovascular disease. Therefore, cautious use, including doses in the lower end of the recommended range, may be warranted in these populations. Reconstitution Directions Reconstitute the lyophilized Levothyroxine Sodium for Injection by aseptically adding 5 mL of 0.9% Sodium Chloride Injection, USP only. Shake vial to ensure complete mixing. The resultant solution will have a final concentration of approximately 20 mcg per mL and 40 mcg per mL for the 100 mcg and 200 mcg vials, respectively. Reconstituted drug product is preservative free and is stable for 4 hours. Discard any unused portion. DO NOT ADD LEVOTHYROXINE SODIUM FOR INJECTION TO OTHER IV FLUIDS. Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit. HOW SUPPLIED Dosage Forms And Strengths Levothyroxine Sodium for Injection is supplied as a lyophilized powder at two strengths in single use amber-colored vials: 100 mcg and 200 mcg. Levothyroxine Sodium for Injection is available in two dosage strengths. Product No. NDC No. Strength Reconstituted Concentration NP506107 63323-649-16 100 mcg/vial 20 mcg/mL NP506247 63323-647-11 200 mcg/vial 40 mcg/mL Storage And Handling Protect from light and store dry product at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature]. Reconstituted drug product is preservative free. Discard any unused portion. This container closure is not made with natural rubber latex. Manufactured by: FreseniusKabi USA, LLC, Lake Zurich, IL 60047. Revised: Aug 2014

INDICATIONS Levothyroxine sodium is used for the following indications Hypothyroidism As replacement or supplemental therapy in congenital or acquired hypothyroidism of any etiology, except transient hypothyroidism during the recovery phase of subacute thyroiditis. Specific indications include: primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) hypothyroidism and subclinical hypothyroidism. Primary hypothyroidism may result from functional deficiency, primary atrophy, partial or total congenital absence of the thyroid gland, or from the effects of surgery, radiation, or drugs, with or without the presence of goiter. Pituitary TSH Suppression In the treatment or prevention of various types of euthyroid goiters (see WARNINGS and PRECAUTIONS), including thyroid nodules (see WARNINGS and PRECAUTIONS), subacute or chronic lymphocytic thyroiditis (Hashimoto's thyroiditis), multinodular goiter (see WARNINGS and PRECAUTIONS) and, as an adjunct to surgery and radioiodine therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer. DOSAGE AND ADMINISTRATION General Principles The goal of replacement therapy is to achieve and maintain a clinical and biochemical euthyroid state. The goal of suppressive therapy is to inhibit growth and/or function of abnormal thyroid tissue. The dose of LEVOTHROID® (levothyroxine sodium) that is adequate to achieve these goals depends on a variety of factors including the patient's age, body weight, cardiovascular status, concomitant medical conditions, including pregnancy, concomitant medications, and the specific nature of the condition being treated (see WARNINGS and PRECAUTIONS). Hence, the following recommendations serve only as dosing guide-lines. Dosing must be individualized and adjustments made based on periodic assessment of the patient's clinical response and laboratory parameters (see PRECAUTIONS, Laboratory Tests). LEVOTHROID® (levothyroxine sodium) is administered as a single daily dose, preferably one-half to one hour before breakfast. LEVOTHROID® (levothyroxine sodium) should be taken at least 4 hours apart from drugs that are known to interfere with its absorption (see PRECAUTIONS, DRUG INTERACTIONS). Due to the long half-life of levothyroxine, the peak therapeutic effect at a given dose of levothyroxine sodium may not be attained for 4-6 weeks. Caution should be exercised when administering LEVOTHROID® (levothyroxine sodium) to patients with underlying cardiovascular disease, to the elderly, and to those with concomitant adrenal insufficiency (see PRECAUTIONS). Specific Patient Populations Hypothyroidism in Adults and in Children in Whom Growth and Puberty are Complete (see WARNINGS and PRECAUTIONS, Laboratory Tests ) Therapy may begin at full replacement doses in otherwise healthy individuals less than 50 years old and in those older than 50 years who have been recently treated for hyperthyroidism or who have been hypothyroid for only a short time (such as a few months). The average full replacement dose of levothyroxine sodium is approximately 1. 7 mcg/kg/day (e. g. , 100-125 mcg/day for a 70 kg adult). Older patients may require less than 1 mcg/kg/day. Levothyroxine sodium doses greater than 200 mcg/day are seldom required. An inadequate response to daily doses ≥ 300 mcg/day is rare and may indicate poor compliance, malabsorption, and/or drug interactions. For most patients older than 50 years or for patients under 50 years of age with underlying cardiac disease, an initial starting dose of 25-50 mcg/day of levothyroxine sodium is recommended, with gradual increments in dose at 6-8 week intervals, as needed. The recommended starting dose of levothyrox-ine sodium in elderly patients with cardiac disease is 12. 5-25 mcg/day, with gradual dose increments at 4-6 week intervals. The levothyroxine sodium dose is generally adjusted in 12. 5-25 mcg increments until the patient with primary hypothyroidism is clinically euthyroid and the serum TSH has normalized. In patients with severe hypothyroidism, the recommended initial levothyroxine sodium dose is 12. 5-25 mcg/day with increases of 25 mcg/day every 2-4 weeks, accompanied by clinical and laboratory assessment, until the TSH level is normalized. In patients with secondary (pituitary) or tertiary (hypothalamic) hypothyroidism, the levothyroxine sodium dose should be titrated until the patient is clinically euthyroid and the serum free-T4 level is restored to the upper half of the normal range. Pediatric Dosage Congenital or Acquired Hypothyroidism (see PRECAUTIONS, Laboratory Tests) General Principles In general, levothyroxine therapy should be instituted at full replacement doses as soon as possible. Delays in diagnosis and institution of therapy may have deleterious effects on the child's intellectual and physical growth and development. Undertreatment and overtreatment should be avoided (see PRECAUTIONS, Pediatric Use). LEVOTHROID® (levothyroxine sodium) may be administered to infants and children who cannot swallow intact tablets by crushing the tablet and suspending the freshly crushed tablet in a small amount (5-10 mL or 1-2 teaspoons) of water. This suspension can be administered by spoon or dropper. DO NOT STORE THE SUSPENSION. Foods that decrease absorption of levothyroxine, such as soybean infant formula, should not be used for administering levothyroxine sodium tablets (see PRECAUTIONS, Drug-Food Interactions). Newborns The recommended starting dose of levothyroxine sodium in newborn infants is 10-15 mcg/kg/day. A lower starting dose (e. g. , 25 mcg/day) should be considered in infants at risk for cardiac failure, and the dose should be increased in 4-6 weeks as needed based on clinical and laboratory response to treatment. In infants with very low (< 5 mcg/dL) or undetectable serum T4 concentrations, the recommended initial starting dose is 50 mcg/day of levothy-roxine sodium. Infants and Children Levothyroxine therapy is usually initiated at full replacement doses, with the recommended dose per body weight decreasing with age (see Table 3). However, in children with chronic or severe hypothyroidism, an initial dose of 25 mcg/day of levothyroxine sodium is recommended with increments of 25 mcg every 2-4 weeks until the desired effect is achieved. Hyperactivity in an older child can be minimized if the starting dose is one-fourth of the recommended full replacement dose, and the dose is then increased on a weekly basis by an amount equal to one-fourth the full-recommended replacement dose until the full recommended replacement dose is reached. Table 3: Levothyroxine Sodium Dosing Guidelines for Pediatric Hypothyroidism AGE Daily Dose Per Kg Body Weighta 0-3 months 10-15 mcg/kg/day 3-6 months 8-10 mcg/kg/day 6-12 months 6-8 mcg/kg/day 1-5 years 5-6 mcg/kg/day 6-12 years 4-5 mcg/kg/day > 12 years but growth and puberty incomplete 2-3 mcg/kg/day Growth and puberty complete 1.7 mcg/kg/day aThe dose should be adjusted based on clinical response and laboratory parameters (see PRECAUTIONS, Laboratory Tests and Pediatric Use). Pregnancy Pregnancy may increase levothyroxine requirements (see Pregnancy). Subclinical Hypothyroidism If this condition is treated, a lower levothyroxine sodium dose (e. g. , 1 mcg/kg/day) than that used for full replacement may be adequate to normalize the serum TSH level. Patients who are not treated should be monitored yearly for changes in clinical status and thyroid laboratory parameters. TSH Suppression in Well-differentiated Thyroid Cancer and Thyroid Nodules The target level for TSH suppression in these conditions has not been established with controlled studies. In addition, the efficacy of TSH suppression for benign nodular disease is controversial. Therefore, the dose of LEVOTHROID® (levothyroxine sodium) used for TSH suppression should be individualized based on the specific disease and the patient being treated. In the treatment of well-differentiated (papillary and follicular) thyroid cancer, levothyroxine is used as an adjunct to surgery and radioiodine therapy. Generally, TSH is suppressed to < 0.1 mU/L, and this usually requires a levothyroxine sodium dose of greater than 2 mcg/kg/day. However, in patients with high-risk tumors, the target level for TSH suppression may be < 0.01 mU/L. In the treatment of benign nodules and nontoxic multinodular goiter, TSH is generally suppressed to a higher target (e. g. , 0.1 to either 0.5 or 1.0 mU/L) than that used for the treatment of thyroid cancer. Levothyroxine sodium is contraindicated if the serum TSH is already suppressed due to the risk of precipitating overt thyrotoxicosis (see CONTRAINDICATIONS, WARNINGS and PRECAUTIONS). Myxedema Coma Myxedema coma is a life-threatening emergency characterized by poor circulation and hypometabolism, and may result in unpredictable absorption of levothyroxine sodium from the gastrointestinal tract. Therefore, oral thyroid hormone drug products are not recommended to treat this condition. Thyroid hormone drug products formulated for intravenous administration should be administered. HOW SUPPLIED LEVOTHROID® (levothyroxine sodium tablets, USP) are caplet-shaped, color-coded, potency marked tablets and are supplied as follows: Strength (mcg) Color NDC # for bottles of 100 NDC # for bottles of 1000 25 Orange NDC 0456-1320-01 NDC 0456-1320-00 50 White NDC 0456-1321-01 NDC 0456-1321-00 75 Violet NDC 0456-1322-01 NDC 0456-1322-00 88 Mint Green NDC 0456-1329-01 NDC 0456-1329-00 100 Yellow NDC 0456-1323-01 NDC 0456-1323-00 112 Rose NDC 0456-1330-01 NDC 0456-1330-00 125 Brown NDC 0456-1324-01 NDC 0456-1324-00 137 Deep Blue NDC 0456-1331-01 NDC 0456-1331-00 150 Blue NDC 0456-1325-01 NDC 0456-1325-00 175 Lilac NDC 0456-1326-01 NDC 0456-1326-00 200 Pink NDC 0456-1327-01 NDC 0456-1327-00 300 Green NDC 0456-1328-01 NDC 0456-1328-00 Storage Conditions Store at 25°C (77°F) with excursions permitted to 15-30°C (59-86°F). Protect from moisture and light. Manufactured for: Forest Pharmaceuticals, Inc., Subsidiary of Forest Laboratories, Inc.,St. Louis, Missouri, 63045 by: Lloyd Pharmaceutical Division of Lloyd, Inc., Shenandoah, IA 51601 Rev. 09/05 FDA rev date: 03/10/2006

PATIENT INFORMATION No information provided. Please refer to the WARNINGS AND PRECAUTIONS sections.

OVERDOSE The signs and symptoms of overdosage are those of hyperthyroidism (see PRECAUTIONS and ADVERSE REACTIONS). In addition, confusion and disorientation may occur. Cerebral embolism, shock, coma, and death have been reported. Seizures have occurred in a child ingesting 18 mg of levothyroxine. Symptoms may not necessarily be evident or may not appear until several days after ingestion of levothyroxine sodium. Treatment Of Overdosage Levothyroxine sodium should be reduced in dose or temporarily discontinued if signs or symptoms of overdosage occur. Acute Massive Overdosage This may be a life-threatening emergency, therefore, symptomatic and supportive therapy should be instituted immediately. If not contraindicated (e.g., by seizures, coma, or loss of the gag reflex), the stomach should be emptied by emesis or gastric lavage to decrease gastrointestinal absorption. Activated charcoal or cholestyramine may also be used to decrease absorption. Central and peripheral increased sympathetic activity may be treated by administering β-receptor antagonists, e.g., propranolol, provided there are no medical contraindications to their use. Provide respiratory support as needed; control congestive heart failure and arrhythmia; control fever, hypoglycemia, and fluid loss as necessary. Large doses of antithyroid drugs (e.g., methimazole or propylthiouracil) followed in one to two hours by large doses of iodine may be given to inhibit synthesis and release of thyroid hormones. Glucocorticoids may be given to inhibit the conversion of T4 to T3. Plasmapheresis, charcoal hemoperfusion and exchange transfusion have been reserved for cases in which continued clinical deterioration occurs despite conventional therapy. Because T4 is highly protein bound, very little drug will be removed by dialysis. CONTRAINDICATIONS Levothyroxine is contraindicated in patients with untreated subclinical (suppressed serum TSH level with normal T3 and T4 levels) or overt thyrotoxicosis of any etiology and in patients with acute myocardial infarction. Levothyroxine is contraindicated in patients with uncorrected adrenal insufficiency since thyroid hormones may precipitate an acute adrenal crisis by increasing the metabolic clearance of glucocorticoids (see PRECAUTIONS). UNITHROID is contraindicated in patients with hypersensitivity to any of the inactive ingredients in UNITHROID tablets. (See DESCRIPTION, Inactive Ingredients).

OVERDOSE The signs and symptoms of overdosage are those of hyperthyroidism (see PRECAUTIONS and ADVERSE REACTIONS). In addition, confusion and disorientation may occur. Cerebral embolism, shock, coma, and death have been reported. Seizures have occurred in a child ingesting 18 mg of levothyroxine. Symptoms may not necessarily be evident or may not appear until several days after ingestion of levothyroxine sodium. Treatment Of Overdosage Levothyroxine sodium should be reduced in dose or temporarily discontinued if signs or symptoms of overdosage occur. Acute Massive Overdosage This may be a life-threatening emergency, therefore, symptomatic and supportive therapy should be instituted immediately. If not contraindicated (e.g., by seizures, coma, or loss of the gag reflex), the stomach should be emptied by emesis or gastric lavage to decrease gastrointestinal absorption. Activated charcoal or cholestyramine may also be used to decrease absorption. Central and peripheral increased sympathetic activity may be treated by administering β-receptor antagonists, e.g., propranolol, provided there are no medical contraindications to their use. Provide respiratory support as needed; control congestive heart failure and arrhythmia; control fever, hypoglycemia, and fluid loss as necessary. Large doses of antithyroid drugs (e.g., methimazole or propylthiouracil) followed in one to two hours by large doses of iodine may be given to inhibit synthesis and release of thyroid hormones. Glucocorticoids may be given to inhibit the conversion of T4 to T3. Plasmapheresis, charcoal hemoperfusion and exchange transfusion have been reserved for cases in which continued clinical deterioration occurs despite conventional therapy. Because T4 is highly protein bound, very little drug will be removed by dialysis. CONTRAINDICATIONS Levothyroxine is contraindicated in patients with untreated subclinical (suppressed serum TSH level with normal T3 and T4 levels) or overt thyrotoxicosis of any etiology and in patients with acute myocardial infarction. Levothyroxine is contraindicated in patients with uncorrected adrenal insufficiency since thyroid hormones may precipitate an acute adrenal crisis by increasing the metabolic clearance of glucocorticoids (see PRECAUTIONS). SYNTHROID is contraindicated in patients with hypersensitivity to any of the inactive ingredients in SYNTHROID tablets (See DESCRIPTION - Inactive Ingredients).

OVERDOSE The signs and symptoms of overdosage are those of hyperthyroidism (see PRECAUTIONS and ADVERSE REACTIONS). In addition, confusion and disorientation may occur. Cerebral embolism, shock, coma, and death have been reported. Seizures have occurred in a child ingesting approximately 20 mg of levothyroxine. Symptoms may not necessarily be evident or may not appear until several days after ingestion of levothyroxine sodium. Treatment Of Overdosage Levothyroxine sodium should be reduced in dose or temporarily discontinued if signs or symptoms of overdosage occur. Acute Massive Overdosage This may be a life-threatening emergency, therefore, symptomatic and supportive therapy should be instituted immediately. If not contraindicated (e.g., by seizures, coma, or loss of the gag reflex), the stomach should be emptied by emesis or gastric lavage to decrease gastrointestinal absorption. Activated charcoal or cholestyramine may also be used to decrease absorption. Central and peripheral increased sympathetic activity may be treated by administering B-receptor antagonists, e.g., propranolol (1 to 3 mg intravenously over a 10- minute period, or orally, 80 to 160 mg/day). Provide respiratory support as needed; control congestive heart failure; control fever, hypoglycemia, and fluid loss as necessary. Glucocorticoids may be given to inhibit the conversion of T4 to T3. Because T4 is highly protein bound, very little drug will be removed by dialysis. CONTRAINDICATIONS Levothyroxine is contraindicated in patients with untreated subclinical (suppressed serum TSH level with normal T3 and T4 levels) or overt thyrotoxicosis of any etiology and in patients with acute myocardial infarction. Levothyroxine is contraindicated in patients with uncorrected adrenal insufficiency since thyroid hormones may precipitate an acute adrenal crisis by increasing the metabolic clearance of glucocorticoids (see PRECAUTIONS ). LEVOXYL is contraindicated in patients with hypersensitivity to any of the inactive ingredients in LEVOXYL tablets (see DESCRIPTION, Inactive Ingredients).

OVERDOSE In general, the signs and symptoms of overdosage with levothyroxine are those of hyperthyroidism [see WARNINGS AND PRECAUTIONS and ADVERSE REACTIONS]. In addition, confusion and disorientation may occur. Cerebral embolism, shock, coma, and death have been reported. Excessive doses of Levothyroxine Sodium for Injection (greater than 500 mcg) are associated with cardiac complications in patients with underlying cardiac disease. Treatment Of Overdosage Levothyroxine Sodium for Injection should be reduced in dose or temporarily discontinued if signs or symptoms of overdosage occur. To obtain up-to-date information about the treatment of overdose, a good resource is the certified Regional Poison Control Center. In managing overdosage, consider the possibility of multiple drug overdoses, interaction among drugs, and unusual drug kinetics in the patient. In the event of an overdose, appropriate supportive treatment should be initiated as dictated by the patient's medical status. CONTRAINDICATIONS None.

OVERDOSE The signs and symptoms of overdosage are those of hyperthyroidism (see PRECAUTIONS and ADVERSE REACTIONS). In addition, confusion and disorientation may occur. Cerebral embolism, shock, coma, and death have been reported. Seizures have occurred in a child ingesting 18 mg of levothy-roxine. Symptoms may not necessarily be evident or may not appear until several days after ingestion of levothyroxine sodium. Treatment of Overdosage Levothyroxine sodium should be reduced in dose or temporarily discontinued if signs or symptoms of overdosage occur. Acute Massive Overdosage This may be a life-threatening emergency, therefore, symptomatic and supportive therapy should be instituted immediately. If not contraindicated (e. g. , by seizures, coma, or loss of the gag reflex), the stomach should be emptied by emesis or gastric lavage to decrease gastrointestinal absorption. Activated charcoal or cholestyramine may also be used to decrease absorption. Central and peripheral increased sympathetic activity may be treated by administering β-receptor antagonists, e. g. , propranolol, provided there are no medical contraindications to their use. Provide respiratory support as needed;control congestive heart failure and arrhythmia;control fever, hypoglycemia, and fluid loss as necessary. Large doses of antithyroid drugs (e. g. , methimazole or propylthiouracil) followed in one to two hours by large doses of iodine may be given to inhibit synthesis and release of thyroid hormones. Glucocorticoids may be given to inhibit the conversion of T4 to T3. Plasmapheresis, charcoal hemoperfusion and exchange transfusion have been reserved for cases in which continued clinical deterioration occurs despite conventional therapy. Because T4 is highly protein bound, very little drug will be removed by dialysis. CONTRAINDICATIONS Levothyroxine is contraindicated in patients with untreated subclinical (suppressed serum TSH level with normal T3 and T4 levels) or overt thyrotoxico-sis of any etiology and in patients with acute myocardial infarction. Levothyroxine is contraindicated in patients with uncorrected adrenal insufficiency since thyroid hormones may precipitate an acute adrenal crisis by increasing the metabolic clearance of glucocorticoids (see PRECAUTIONS). LEVOTHROID® (levothyroxine sodium) is contraindicated in patients with hypersensitivity to any of the inactive ingredients in LEVOTHROID® tablets (see DESCRIPTION, Inactive Ingredients).

SIDE EFFECTS Adverse reactions associated with levothyroxine therapy are primarily those of hyperthyroidism due to therapeutic overdosage (see PRECAUTIONS and OVERDOSAGE). They include the following: General: fatigue, increased appetite, weight loss, heat intolerance, fever, excessive sweating; Central nervous system: headache, hyperactivity, nervousness, anxiety, irritability, emotional lability, insomnia; Musculoskeletal: tremors, muscle weakness; Cardiovascular: palpitations, tachycardia, arrhythmias, increased pulse and blood pressure, heart failure, angina, myocardial infarction, cardiac arrest; Respiratory: dyspnea; Gastrointestinal: diarrhea, vomiting, abdominal cramps and elevation in liver function tests; Dermatologic: hair loss; flushing; Endocrine: decreased bone mineral density; Reproductive: menstrual irregularities, impaired fertility. Pseudotumor cerebri and slipped capital femoral epiphysis have been reported in children receiving levothyroxine therapy. Overtreatment may result in craniosynostosis in infants and premature closure of the epiphyses in children with resultant compromised height. Seizures have been reported rarely with the institution of levothyroxine therapy. Inadequate levothyroxine dosage will produce or fail to ameliorate the signs and symptoms of hypothyroidism. Hypersensitivity reactions to inactive ingredients have occurred in patients treated with thyroid hormone products. These include urticaria, pruritus, skin rash, flushing, angioedema, various Gl symptoms (abdominal pain, nausea, vomiting and diarrhea), fever, arthralgia, serum sickness and wheezing. Hypersensitivity to levothyroxine itself is not known to occur. DRUG INTERACTIONS Many drugs affect thyroid hormone pharmacokinetics and metabolism (e.g., absorption, synthesis, secretion, catabolism, protein binding, and target tissue response) and may alter the therapeutic response to UNITHROID. In addition, thyroid hormones and thyroid status have varied effects on the pharmacokinetics and action of other drugs. A listing of drug-thyroidal axis interactions is contained in Table 2. The list of drug-thyroidal axis interactions in Table 2 may not be comprehensive due to the introduction of new drugs that interact with the thyroidal axis or the discovery of previously unknown interactions. The prescriber should be aware of this fact and should consult appropriate reference credits (e.g., package inserts of newly approved drugs, medical literature) for additional information if a drug-drug interaction with levothyroxine is suspected. Table 2: Drug-Thyroidal Axis Interactions Drug or Drug Class Effect Drugs that may reduce TSH secretion - the reduction is not sustained; therefore, hypothyroidism does not occur Dopamine/Dopamine Agonists Glucocorticoids Octreotide Use of these agents may result in a transient reduction in TSH secretion when administered at the following doses: dopamine ( ≥ 1 mcg/kg/min ); Glucocorticoids (hydrocortisone ≥ 100 mg/day or equivalent); Octreotide ( > 100 mcg/day). Drugs that alter thyroid hormone secretion Drugs that may decrease thyroid hormone secretion, which may result in hypothyroidism Aminoglutethimide Amiodarone Iodide (including iodine-containing Radiographic contrast agents) Lithium Methimazole Propylthioracil (PTU) Sulfonamides Tolbutamide Long-term lithium therapy can result in goiter in up to 50% of patients, and either subclinical or overt hypothyroidism, each in up to 20% of patients. The fetus, neonate, elderly and euthyroid patients with underlying thyroid disease (e.g., Hashimoto's thyroiditis or with Grave's disease previously treated with radioiodine or surgery) are among those individuals who are particularly susceptible to iodine-induced hypothyroidism. Oral cholecystographic agents and amiodarone are slowly excreted, producing more prolonged hypothyroidism than parenterally administered iodinated contrast agents. Long-term amino-glutethimide therapy may minimally decrease T4 and T3 levels and increase TSH, although all values remain within normal limits in most patients. Drugs that may increase thyroid hormone secretion, which may result in hyperthyroidism Amiodarone Iodide (including iodine-containing Radiographic contrast agents) Iodide and drugs that contain pharmacologic amounts of iodide may cause hyperthyroidism in euthyroid patients with Grave's disease previously treated with antithyroid drugs or in euthyroid patients with thyroid autonomy (e.g., multinodular goiter or hyper functioning thyroid adenoma). Hyperthyroidism may develop over several weeks and may persist for several months after therapy discontinuation. Amiodarone may induce hyperthyroidism by causing thyroiditis. Drugs that may decrease T4 absorption, which may result in hypothyroidism Antacids - Aluminum & Magnesium Hydroxides - Simethicone Bile Acid Sequestrants - Cholestyramine - Colestipol Calcium Carbonate Cation Exchange Resins - Kayexalate Ferrous Sulfate Orlistat Sucralfate Concurrent use may reduce the efficacy of levothyroxine by binding and delaying or preventing absolution, potentially resulting in hypothyroidism. Calcium carbonate may form an insoluble chelate with levothyroxine, and ferrous sulfate likely forms a ferric-thyroxine complex. Administer levothyroxine at least 4 hours apart from these agents. Patients treated concomitantly with orlistat and levothyroxine should be monitored for changes in thyroid function. Drugs that may alter T4 and T3 serum transport - but FT4 concentration remains normal; and, therefore, the patient remains euthyroid Drugs that may increase serum TBG concentration Drugs that may decrease serum TBG concentration Clofibrate Estrogen-containing oral contraceptives Estrogens (oral) Heroin / Methadone 5-Fluorouracil Mitotane Tamoxifen Androgens / Anabolic Steroids Asparaginase Glucocorticoids Slow-Release Nicotinic Acid Drugs that may cause protein-binding site displacement Furosemide ( > 80 mg IV) Heparin Hydantoins Non Steroidal Anti-lnflammatory Drugs - Fenamates - Phenylbutazone Salicylates ( > 2 g/day) Administration of these agents with levothyroxine results in an initial transient increase in FT4. Continued administration results in a decrease in serum T4 and normal FT4 and TSH concentrations and, therefore, patients are clinically euthyroid. Salicylates inhibit binding of T4 and T3 to TBG and transthyretin. An initial increase in serum FT4, is followed by return of FT4 to normal levels with sustained therapeutic serum salicylate concentrations, although total-T4 levels may decrease by as much as 30%. Drugs that may alter T4 and T3 metabolism Drugs that may increase hepatic metabolism, which may result in hypothyroidism Carbamazepine Hydantoins Phenobarbital Rifampin Stimulation of hepatic microsomal drug-metabolizing enzyme activity may cause increased hepatic degradation of levo-thyroxine, resulting in increased Ievothyroxine requirements. Phenytoin and carbamazepine reduce serum protein binding of levothyroxine, and total - and free-T4 may be reduced by 20% to 40%, but most patients have normal senjm TSH levels and are clinically euthyroid. Drugs that may decrease T4 5' - deiodinase activity Amiodarone Beta-adrenergic antagonists - (e.g., Propranolol > 160 mg/day) Glucocorticoids -(e.g., Dexamethasone ≥ 4 mg/day) Propylthiouracil (PTU) Administration of these enzyme inhibitors decrease the peripheral conversion of T4 to T3, Ieading to decreased T3 levels. However, serum T4 levels are usually normal but may occasionally be slightly increased. In patients treated with large doses of propranolol ( > 160 m g/day), T3 and T4 levels change slightly, TSH levels remain normal, and patients are clinically euthyroid. It should be noted that actions of particular beta-adrenergic antagonists may be impaired when the hypothyroid patient is converted to the euthyroid state. Short-term administration of large doses of glucocorticoids may decrease serum T3 concentrations by 30% with minimal change in serum T4levels. However, long-term glucocorticoid therapy may result in slightly decreased T3 and T4 levels due to decreased TBG production (see above). Miscellaneous Anticoagulants (oral) - Coumarin Derivatives - Indandione Derivatives Thyroid hormones appear to increase the catabolism of vitamin K-dependent clotting factors, thereby increasing the anticoagulant activity of oral anticoagulants. Concomitant use of these agents impairs the compensatory increases in clotting factor synthesis. Prothrombin time should be carefully monitored in patients taking levothyroxine and oral anticoagulants and the dose of anticoagulant therapy adjusted accordingly. Antidepressants - Tricyclics (e.g., Amitriptyline) - Tetracyclics (e.g., Maprotiline) - Selective Serotonin Reuptake Inhibitors (SSRls, e.g., Sertraline) Concurrent use of tri/tetracyclic antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines.Toxic effects may include increased risk of cardiac arrhythmias and CNS stimulation, onset of action of tricyclics may be accelerated. Administration of sertraline in patients stabilized on levothyroxine may result in increased levothyroxine requirements. Antidiabetic Agents - Biguanides - Meglitinides - Sulfonylureas - Thiazolidediones - Insulin Addition of levothyroxine to antidiabetic or insulin therapy may result in increased antidiabetic agent or insulin requirements. Careful monitoring of diabetic control is recommended, especially when thyroid therapy is started, changed, or discontinued. Cardiac Glycosides Serum digitalis glycoside levels may be reduced in hyperthyroidism or when the hypothyroid patient is converted to the euthyroid state. Therapeutic effect of digitalis glycosides may be reduced. Cytokines - Interferon-α- Interleukin-2 Therapy with interferon-a has been associated with the development of antithyroid microsomal antibodies in 20% of patients and some have transient hypothyroidism, hyperthyroidism, or both. Patients who have antithyroid antibodies before treatment are at higher risk for thyroid dysfunction during treatment. Interleukin-2 has been associated with transient painless thyroiditis in 20% of patients. Interferon-p and -y have not been reported to cause thyroid dysfunction. Growth Hormones - Somatrem - Somatropin Excessive use of thyroid hormones with growth hormones may accelerate epiphyseal closure. However, untreated hypothyroidism may interfere with growth response to growth hormone. Ketamine Concurrent use may produce marked hypertension and tachycardia, cautious administration to patients receiving thyroid hormone therapy is recommended. Methylxanthine Bronchodilators - (e.g., Theophylline) Decreased theophylline clearance may occur in hypothyroid patients, clearance returns to normal when the euthyroid state is achieved. Radiographic Agents Thyroid hormones may reduce the uptake of 123I, 1311, and 99mTc. Sympathomimetics Concurrent use may increase the effects of sympathomimetics or thyroid hormone. Thyroid hormones may increase the risk of coronary insufficiency when sympathomimetic agents are administered to patients with coronary artery disease. Chloral Hydrate Diazepam Ethionamide Lovastatin Metoclopramide 6-Mercaptopurine Nitroprusside Para-aminosalicylate sodium Perphenazine Resorcinol (excessive topical use) Thiazide Diuretics These agents have been associated with thyroid hormone and/or TSH level alterations by various mechanisms. Oral Anticoagulants Levothyroxine increases the response to oral anticoagulant therapy. Therefore, a decrease in the dose of anticoagulant may be warranted with correction of the hypothyroid state or when the UNITHROID dose is increased. Prothrombin time should be closely monitored to permit appropriate and timely dosage adjustments (see Table 2). Digitalis Glycosides The therapeutic effects of digitalis glycosides may be reduced by levothyroxine. Serum digitalis glycoside levels may be decreased when a hypothyroid patient becomes euthyroid, necessitating an increase in the dose of digitalis glycosides (see Table 2). Drug-Food Interactions Consumption of certain foods may affect levothyroxine absorption thereby necessitating adjustments in dosing. Soybean flour (infant formula), cotton seed meal, walnuts, and dietary fiber may bind and decrease the absorption of levothyroxine sodium from the Gl tract. Drug-Laboratory Test Interactions Changes in TBG concentration must be considered when interpreting T4 and T3 values, which necessitates measurement and evaluation of unbound (free) hormone and/or determination of the free T4 index (FT4I). Pregnancy, infectious hepatitis, estrogens, estrogen-containing oral contraceptives, and acute intermittent porphyria increase TBG concentrations. Decreases in TBG concentrations are observed in nephrosis, severe hypoproteinemia, severe liver disease, acromegaly, and after androgen or corticosteroid therapy (see also Table 2). Familial hyper- or hypothyroxine binding globulinemias have been described, with the incidence of TBG deficiency approximating 1 in 9000.

SIDE EFFECTS Adverse reactions associated with levothyroxine therapy are primarily those of hyperthyroidism due to therapeutic overdosage (see PRECAUTIONS and OVERDOSE). They include the following: General fatigue, increased appetite, weight loss, heat intolerance, fever, excessive sweating; Central Nervous System headache, hyperactivity, nervousness, anxiety, irritability, emotional lability, insomnia; Musculoskeletal tremors, muscle weakness; Cardiovascular palpitations, tachycardia, arrhythmias, increased pulse and blood pressure, heart failure, angina, myocardial infarction, cardiac arrest; Respiratory dyspnea; Gastrointestinal diarrhea, vomiting, abdominal cramps and elevations in liver function tests; Dermatologic hair loss, flushing; Endocrine decreased bone mineral density; Reproductive menstrual irregularities, impaired fertility. Pseudotumor cerebri and slipped capital femoral epiphysis have been reported in children receiving levothyroxine therapy. Overtreatment may result in craniosynostosis in infants and premature closure of the epiphyses in children with resultant compromised adult height. Seizures have been reported rarely with the institution of levothyroxine therapy. Inadequate levothyroxine dosage will produce or fail to ameliorate the signs and symptoms of hypothyroidism. Hypersensitivity reactions to inactive ingredients have occurred in patients treated with thyroid hormone products. These include urticaria, pruritus, skin rash, flushing, angioedema, various GI symptoms (abdominal pain, nausea, vomiting and diarrhea), fever, arthralgia, serum sickness and wheezing. Hypersensitivity to levothyroxine itself is not known to occur. DRUG INTERACTIONS Many drugs affect thyroid hormone pharmacokinetics and metabolism (e.g., absorption, synthesis, secretion, catabolism, protein binding, and target tissue response) and may alter the therapeutic response to SYNTHROID. In addition, thyroid hormones and thyroid status have varied effects on the pharmacokinetics and actions of other drugs. A listing of drug-thyroidal axis interactions is contained in Table 2. The list of drug-thyroidal axis interactions in Table 2 may not be comprehensive due to the introduction of new drugs that interact with the thyroidal axis or the discovery of previously unknown interactions. The prescriber should be aware of this fact and should consult appropriate reference sources (e.g., package inserts of newly approved drugs, medical literature) for additional information if a drug-drug interaction with levothyroxine is suspected. Table 2. Drug-Thyroidal Axis Interactions Drug or Drug Class Effect Drugs that may reduce TSH secretion – the reduction is not sustained; therefore, hypothyroidism does not occur Dopamine/Dopamine Agonists Glucocorticoids Octreotide Use of these agents may result in a transient reduction in TSH secretion when administered at the following doses: Dopamine (≥ 1 mcg/kg/min); Glucocorticoids (hydrocortisone ≥ 100 mg/day or equivalent); Octreotide (> 100 mcg/day). Drugs that alter thyroid hormone secretion Drugs that may decrease thyroid hormone secretion, which may result in hypothyroidism Aminoglutethimide Amiodarone Iodide (including iodine-containing radiographic contrast agents) LithiumMethimazole Propylthiouracil (PTU) Sulfonamides Tolbutamide Long-term lithium therapy can result in goiter in up to 50% of patienradioiodine or surgery) are among those individuals who are particularly susceptible to iodine-induced hypothyroidism. Oral cholecystographic agents and amiodarone are slowly excreted, producing more prolonged hypothyroidism than parenterally administered iodinated contrast agents. Long-term aminoglutethimide therapy may minimally decrease T and T levels and increase TSH, although all values remain within normal limits in most patients.ts, and either subclinical or overt hypothyroidism, each in up to 20% of patients. The fetus, neonate, elderly and euthyroid patients with underlying thyroid disease (e.g., ashimoto's thyroiditis or with Grave's disease previously treated with radioiodine or surgery) are among those individuals who are particularly susceptible to iodine-induced hypothyroidism. Oral cholecystographic agents and amiodarone are slowly excreted, producing more prolonged hypothyroidism than parenterally administered iodinated contrast agents. Long-term aminoglutethimide therapy may minimally decrease T and T levels and increase TSH, although all values remain within normal limits in most patients. Drugs that may increase thyroid hormone secretion, which may result in hyperthyroidism Amiodarone Iodide (including iodine-containing radiographic contrast agents) Iodide and drugs that contain pharmacologic amounts of iodide may cause hyperthyroidism in euthyroid patients with Grave's disease previously treated with antithyroid drugs or in euthyroid patients with thyroid autonomy (e.g., multinodular goiter or hyperfunctioning thyroid adenoma). Hyperthyroidism may develop over several weeks and may persist for several months after therapy discontinuation. Amiodarone may induce hyperthyroidism by causing thyroiditis. Drugs that may decrease T4 absorption, which may result in hypothyroidism Antacids - Aluminum & Magnesium Hydroxides - Simethicone Bile Acid Sequestrants - Cholestyramine - Colestipol Calcium Carbonate Cation Exchange Resins - Kayexalate Ferrous Sulfate Orlistat Sucralfate Concurrent use may reduce the efficacy of levothyroxine by binding and delaying or preventing absorption, potentially resulting in hypothyroidism. Calcium carbonate may form an insoluble chelate with levothyroxine, and ferrous sulfate likely forms a ferric-thyroxine complex. Administer levothyroxine at least 4 hours apart from these agents. Patients treated concomitantly with orlistat and levothyroxine should be monitored for changes in thyroid function. Drugs that may alter T4 and T3 serum transport - but FT4 concentration remains normal; and therefore, the patient remains euthyroid Drugs that may increase serum TBG concentration Drugs that may decrease serum TBG concentration Clofibrate Estrogen-containing oral contraceptives Estrogens (oral) Heroin / Methadone 5-Fluorouracil Mitotane Tamoxifen Androgens / Anabolic Steroids Asparaginase Glucocorticoids Slow-Release Nicotinic Acid Drugs that may cause protein-binding site displacement Furosemide (> 80 mg IV) Heparin Hydantoins Non Steroidal Anti-Inflammatory Drugs - Fenamates - Phenylbutazone Salicylates (> 2 g/day) Administration of these agents with levothyroxine results in an initial transient increase in FT4. Continued administration results in a decrease in serum T4 and normal FT4 and TSH concentrations and, therefore, patients are clinically euthyroid. Salicylates inhibit binding of T4 and T3 to TBG and transthyretin. An initial increase in serum FT4 is followed by return of FT4 to normal levels with sustained therapeutic serum salicylate concentrations, although total-T4 levels may decrease by a much as 30%. Drugs that may alter T4 and T3 metabolism Drugs that may increase hepatic metabolism, which may result in hypothyroidism Carbamazepine Hydantoins Phenobarbital Rifampin Stimulation of hepatic microsomal drug-metabolizing enzyme activity may cause increased hepatic degradation of levothyroxine, resulting in increased levothyroxine requirements. Phenytoin and carbamazepine reduce serum protein binding of levothyroxine, and total- and free- T4 may be reduced by 20% to 40%, but most patients have normal serum TSH levels and are clinically euthyroid. Drugs that may decrease T4 5'-deiodinase activity Amiodarone Beta-adrenergic antagonists - (e.g., Propranolol > 160 mg/day) Glucocorticoids - (e.g., Dexamethasone ≥ 4 mg/day) Propylthiouracil (PTU) Administration of these enzyme inhibitors decreases the peripheral conversion of T4 to T3, leading to decreased T3 levels. However, serum T levels are usually normal but may occasionally be slightly increased. In patients treated with large doses of propranolol (> 160 mg/day), T3 and T4 levels change slightly, TSH levels remain normal, and patients are clinically euthyroid. It should be noted that actions of particular betaadrenergic antagonists may be impaired when the hypothyroid patient is converted to the euthyroid state. Short-term dministration of large doses of glucocorticoids may decrease serum T3 concentrations by 30% with minimal change in serum T4 levels. However, long-term glucocorticoid therapy may result in slightly decreased T3 and T4 levels due to decreased TBG production (see above). Miscellaneous Anticoagulants (oral) - Coumarin Derivatives - Indandione Derivatives Thyroid hormones appear to increase the catabolism of vitamin K-dependent clotting factors, thereby increasing the anticoagulant activity of oral anticoagulants. Concomitant use of these agents impairs the compensatory increases in clotting factor synthesis. Prothrombin time should be carefully monitored in patients taking levothyroxine and oral anticoagulants and the dose of anticoagulant therapy adjusted accordingly. Antidepressants - Tricyclics (e.g., Amitriptyline) - Tetracyclics (e.g., Maprotiline) - Selective Serotonin Reuptake Inhibitors (SSRIs; e.g., Sertraline) Concurrent use of tri/tetracyclic antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. Toxic effects may include increased risk of cardiac arrhythmias and CNS stimulation; onset of action of tricyclics may be accelerated. Administration of sertraline in patients stabilized on levothyroxine may result in increased levothyroxine requirements. Antidiabetic Agents - Biguanides - Meglitinides - Sulfonylureas - Thiazolidinediones - Insulin Addition of levothyroxine to antidiabetic or insulin therapy may result in increased antidiabetic agent or insulin requirements. Careful monitoring of diabetic control is recommended, especially when thyroid therapy is started, changed, or discontinued. Cardiac Glycosides Serum digitalis glycoside levels may be reduced in hyperthyroidism or when the hypothyroid patient is converted to the euthyroid state. Therapeutic effect of digitalis glycosides may be reduced. Cytokines - Interferon-α - Interleukin-2 Therapy with interferon-α has been associated with the development of antithyroid microsomal antibodies in 20% of patients and some have transient hypothyroidism, hyperthyroidism, or both. Patients who have antithyroid antibodies before treatment are at higher risk for thyroid dysfunction during treatment. Interleukin-2 has been associated with transient painless thyroiditis in 20% of patients. Interferon-β and -γ have not been reported to cause thyroid dysfunction. Growth Hormones - Somatrem - Somatropin Excessive use of thyroid hormones with growth hormones may accelerate epiphyseal closure. However, untreated hypothyroidism may interfere with growth response to growth hormone. Ketamine Concurrent use may produce marked hypertension and tachycardia; cautious administration to patients receiving thyroid hormone therapy is recommended. Methylxanthine Bronchodilators - (e.g., Theophylline) Decreased theophylline clearance may occur in hypothyroid patients; clearance returns to normal when the euthyroid state is achieved. Radiographic Agents Thyroid hormones may reduce the uptake of 123I, 131I, and 99mTc. Sympathomimetics Concurrent use may increase the effects of sympathomimetics or thyroid hormone. Thyroid hormones may increase the risk of coronary insufficiency when sympathomimetic agents are administered to patients with coronary artery disease. Chloral Hydrate Diazepam Ethionamide Lovastatin Metoclopramide 6-Mercaptopurine Nitroprusside Para-aminosalicylate sodium Perphenazine Resorcinol (excessive topical use) Thiazide Diuretics These agents have been associated with thyroid hormone and/or TSH level alterations by various mechanisms. Oral Anticoagulants Levothyroxine increases the response to oral anticoagulant therapy. Therefore, a decrease in the dose of anticoagulant may be warranted with correction of the hypothyroid state or when the SYNTHROID dose is increased. Prothrombin time should be closely monitored to permit appropriate and timely dosage adjustments (see Table 2). Digitalis Glycosides The therapeutic effects of digitalis glycosides may be reduced by levothyroxine. Serum digitalis glycoside levels may be decreased when a hypothyroid patient becomes euthyroid, necessitating an increase in the dose of digitalis glycosides (see Table 2).

SIDE EFFECTS Adverse reactions associated with levothyroxine therapy are primarily those of hyperthyroidism due to therapeutic overdosage. They include the following: General: fatigue, increased appetite, weight loss, heat intolerance, fever, excessive sweating; Central nervous system: headache, hyperactivity, nervousness, anxiety, irritability, emotional lability, insomnia; Musculoskeletal: tremors, muscle weakness; Cardiac: palpitations, tachycardia, arrhythmias, increased pulse and blood pressure, heart failure, angina, myocardial infarction, cardiac arrest; Pulmonary: dyspnea; GI: diarrhea, vomiting, abdominal cramps; Dermatologic: hair loss, flushing; Reproductive: menstrual irregularities, impaired fertility. Pseudotumor cerebri and slipped capital femoral epiphysis have been reported in children receiving levothyroxine therapy. Overtreatment may result in craniosynostosis in infants and premature closure of the epiphyses in children with resultant compromised adult height. Seizures have been reported rarely with the institution of levothyroxine therapy. Inadequate levothyroxine dosage will produce or fail to ameliorate the signs and symptoms of hypothyroidism. Hypersensitivity reactions to inactive ingredients have occurred in patients treated with thyroid hormone products. These include urticaria, pruritus, skin rash, flushing, angioedema, various GI symptoms (abdominal pain, nausea, vomiting and diarrhea), fever, arthralgia, serum sickness and wheezing. Hypersensitivity to levothyroxine itself is not known to occur. In addition to the above events, the following have been reported, predominately when Levoxyl tablets were not taken with water: choking, gagging, tablet stuck in throat and dysphagia (see PATIENT INFORMATION). DRUG INTERACTIONS Many drugs affect thyroid hormone pharmacokinetics and metabolism (e.g., absorption, synthesis, secretion, catabolism, protein binding, and target tissue response) and may alter the therapeutic response to LEVOXYL. In addition, thyroid hormones and thyroid status have varied effects on the pharmacokinetics and action of other drugs. A listing of drug-thyroidal axis interactions is contained in Table 2. The list of drug-thyroidal axis interactions in Table 2 may not be comprehensive due to the introduction of new drugs that interact with the thyroidal axis or the discovery of previously unknown interactions. The prescriber should be aware of this fact and should consult appropriate reference sources. (e.g., package inserts of newly approved drugs, medical literature) for additional information if a drug-drug interaction with levothyroxine is suspected. Table 2: Drug - Thyroidal Axis Interactions Drug or Drug Class Effect Drugs that may reduce TSH secretion -the reduction is not sustained; therefore, hypothyroidism does not occur Dopamine / Dopamine Agonists Glucocorticoids Octreotide Use of these agents may result in a transient reduction in TSH secretion when administered at the following doses: Dopamine (≥1 mcg/kg/min); Glucocorticoids (hydrocortisone ≥100 mg/day or equivalent); Octreotide (>100 mcg/day). Drugs that alter thyroid hormone secretion Drugs that may decrease thyroid hormone secretion, which may result in hypothyroidism Aminoglutethimide Amiodarone Iodide (including iodine-containing Radiographic contrast agents) Lithium Methimazole Propylthiouracil (PTU) Sulfonamides Tolbutamide Long-term lithium therapy can result in goiter in up to 50% of patients, and either subclinical or overt hypothyroidism, each in up to 20% of patients. The fetus, neonate, elderly and euthyroid patients with underlying thyroid disease (e.g., Hashimoto's thyroiditis or with Grave's disease previously treated with radioiodine or surgery) are among those individuals who are particularly susceptible to iodineinduced hypothyroidism. Oral cholecystographic agents and amiodarone are slowly excreted, producing more prolonged hypothyroidism than parenterally administered iodinated contrast agents. Long-term aminoglutethimide therapy may minimally decrease T4 and T3 levels and increase TSH, although all values remain within normal limits in most patients. Drugs that may increase thyroid hormone secretion, which may result in hyperthyroidism Amiodarone Iodide (including iodine-containing Radiographic contrast agents) Iodide and drugs that contain pharmacologic amounts of iodide may cause hyperthyroidism in euthyroid patients with Grave's disease previously treated with antithyroid drugs or in euthyroid patients with thyroid autonomy (e.g., multinodular goiter or hyperfunctioning thyroid adenoma). Hyperthyroidism may develop over several weeks and may persist for several months after therapy discontinuation. Amiodarone may induce hyperthyroidism by causing thyroiditis. Drugs that may decrease T4 absorption, which may result in hypothyroidism Antacids - Aluminum & Magnesium Hydroxides - Simethicone Bile Acid Sequestrants - Cholestyramine - Colestipol Calcium Carbonate Cation Exchange Resins - Kayexalate Ferrous Sulfate Orlistat Sucralfate Concurrent use may reduce the efficacy of levothyroxine by binding and delaying or preventing absorption, potentially resulting in hypothyroidism. Calcium carbonate may form an insoluble chelate with levothyroxine, and ferrous sulfate likely forms a ferric-thyroxine complex. Administer levothyroxine at least 4 hours apart from these agents. Patients treated concomitantly with orlistat and levothyroxine should be monitored for changes in thyroid function. Drugs that may alter T4 and T3 serum transport - but FT4 concentration remains normal; and, therefore, the patient remains euthyroid Drugs that may increase serum TBG concentration Drugs that may decrease serum TBG concentration Clofibrate Estrogen-containing oral contraceptives Estrogens (oral) Heroin / Methadone 5-Fluorouracil Mitotane Tamoxifen Androgens / Anabolic Steroids Asparaginase Glucocorticoids Slow-Release Nicotinic Acid Drugs that may cause protein-binding site displacement Furosemide ( > 80 mg IV) Heparin Hydantoins Non Steroidal Anti-Inflammatory Drugs - Fenamates - Phenylbutazone Salicylates ( > 2 g/day) Administration of these agents with levothyroxine results in an initial transient increase in FT4. Continued administration results in a decrease in serum T4 and normal FT4 and TSH concentrations and, therefore, patients are clinically euthyroid. Salicylates inhibit binding of T4 and T3 to TBG and transthyretin. An initial increase in serum FT4 is followed by return of FT4 to normal levels with sustained therapeutic serum salicylate concentrations, although total-T4 levels may decrease by as much as 30%. Drugs that may alter T4 and T3 metabolism Drugs that may increase hepatic metabolism, which may result in hypothyroidism Carbamazepine Hydantoins Phenobarbital Rifampin Stimulation of hepatic microsomal drug-metabolizing enzyme activity may cause increased hepatic degradation of levothyroxine, resulting in increased levothyroxine requirements. Phenytoin and carbamazepine reduce serum protein binding of levothyroxine, and total- and free-T4 may be reduced by 20% to 40%, but most patients have normal serum TSH levels and are clinically euthyroid. Drugs that may decrease T4 5'-deiodinase activity Amiodarone Beta-adrenergic antagonists - (e.g., Propranolol > 160 mg/day) Glucocorticoids - (e.g., Dexamethasone > 4 mg/day) Propylthiouracil (PTU) Administration of these enzyme inhibitors decreases the peripheral conversion of T4 to T3 , leading to decreased T3 levels. However, serum T4 levels are usually normal but may occasionally be slightly increased. In patients treated with large doses of propranolol (>160 mg/day), T3 and T4 levels change slightly, TSH levels remain normal, and patients are clinically euthyroid. It should be noted that actions of particular beta-adrenergic antagonists may be impaired when the hypothyroid patient is converted to the euthyroid state. Short-term administration of large doses of glucocorticoids may decrease serum T3 concentrations by 30% with minimal change in serum T4 levels. However, long-term glucocorticoid therapy may result in slightly decreased T3 and T4 levels due to decreased TBG production (see above). Miscellaneous Anticoagulants (oral) - Coumarin Derivatives - Indandione Derivatives Thyroid hormones appear to increase the catabolism of vitamin K-dependent clotting factors, thereby increasing the anticoagulant activity of oral anticoagulants. Concomitant use of these agents impairs the ompensatory increases in clotting factor synthesis. Prothrombin time should be carefully monitored in patients taking levothyroxine and oral anticoagulants and the dose of anticoagulant therapy adjusted accordingly. Antidepressants - Tricyclics (e.g., Amitriptyline) - Tetracyclics (e.g., Maprotiline) - Selective Serotonin Reuptake Inhibitors (SSRIs; e.g., Sertraline) Concurrent use of tri/tetracyclic antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. Toxic effects may include increased risk of cardiac arrhythmias and CNS stimulation; onset of action of tricyclics may be accelerated. Administration of sertraline in patients stabilized on levothyroxine may result in increased levothyroxine requirements. Antidiabetic Agents - Biguanides - Meglitinides - Sulfonylureas - Thiazolidediones - Insulin Addition of levothyroxine to antidiabetic or insulin therapy may result in increased antidiabetic agent or insulin requirements. Careful monitoring of diabetic control is recommended, especially when thyroid therapy is started, changed, or discontinued. Cardiac Glycosides Serum digitalis glycoside levels may be reduced in hyperthyroidism or when the hypothyroid patient is converted to the euthyroid state. Therapeutic effect of digitalis glycosides may be reduced. Cytokines - Interferon-α - Interleukin-2 Therapy with interferon-α has been associated with the development of antithyroid microsomal antibodies in 20% of patients and some have transient hypothyroidism, hyperthyroidism, or both. Patients who have antithyroid antibodies before treatment are at higher risk for thyroid dysfunction during treatment. Interleukin-2 has been associated with transient painless thyroiditis in 20% of patients. Interferon-β and -γ have not been reported to cause thyroid dysfunction. Growth Hormones - Somatrem - Somatropin Excessive use of thyroid hormones with growth hormones may accelerate epiphyseal closure. However, untreated hypothyroidism may interfere with growth response to growth hormone. Ketamine Concurrent use may produce marked hypertension and tachycardia; cautious administration to patients receiving thyroid hormone therapy is recommended. Methylxanthine Bronchodilators - (e.g., Theophylline) Decreased theophylline clearance may occur in hypothyroid patients; clearance returns to normal when the euthyroid state is achieved. Radiographic Agents Thyroid hormones may reduce the uptake of 123I, 131I, and 99mTc. Sympathomimetics Concurrent use may increase the effects of sympathomimetics or thyroid hormone. Thyroid hormones may increase the risk of coronary insufficiency when sympathomimetic agents are administered to patients with coronary artery disease. Chloral Hydrate Diazepam Ethionamide Lovastatin Metoclopramide 6-Mercaptopurine Nitroprusside Para-aminosalicylate sodium Perphenazine Resorcinol (excessive topical use) Thiazide Diuretics These agents have been associated with thyroid hormone and / or TSH level alterations by various mechanisms. Oral Anticoagulants Levothyroxine increases the response to oral anticoagulant therapy. Therefore, a decrease in the dose of anticoagulant may be warranted with correction of the hypothyroid state or when the LEVOXYL dose is increased. Prothrombin time should be closely monitored to permit appropriate and timely dosage adjustments (see Table 2). Digitalis Glycosides The therapeutic effects of digitalis glycosides may be reduced by levothyroxine. Serum digitalis glycoside levels may be decreased when a hypothyroid patient becomes euthyroid, necessitating an increase in the dose of digitalis glycosides (see Table 2).

SIDE EFFECTS Excessive doses of levothyroxine can predispose to signs and symptoms compatible with hyperthyroidism. The signs and symptoms of thyrotoxicosis include, but are not limited to: exophthalmic goiter, weight loss, increased appetite, palpitations, nervousness, diarrhea, abdominal cramps, sweating, tachycardia, increased pulse and blood pressure, cardiac arrhythmias, angina pectoris, tremors, insomnia, heat intolerance, fever, and menstrual irregularities. DRUG INTERACTIONS Many drugs affect thyroid hormone pharmacokinetics and metabolism (e.g., synthesis, secretion, catabolism, protein binding, and target tissue response) and may alter the therapeutic response to Levothyroxine Sodium for Injection. In addition, thyroid hormones and thyroid status have varied effects on the pharmacokinetics and actions of other drugs (see Pharmacokinetics). Antidiabetic Therapy Addition of levothyroxine to antidiabetic or insulin therapy may result in increased antidiabetic agent or insulin requirements. Careful monitoring of diabetic control is recommended, especially when thyroid therapy is started, changed, or discontinued. Oral Anticoagulants Levothyroxine increases the response to oral anticoagulant therapy. Therefore, a decrease in the dose of anticoagulant may be warranted with correction of the hypothyroid state or when the Levothyroxine Sodium for Injection dose is increased. Prothrombin time should be closely monitored to permit appropriate and timely dosage adjustments. Digitalis Glycosides The therapeutic effects of digitalis glycosides may be reduced by levothyroxine. Serum digitalis glycoside levels may be decreased when a hypothyroid patient becomes euthyroid, necessitating an increase in the dose of digitalis glycosides. Antidepressant Therapy Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines. Toxic effects may include increased risk of cardiac arrhythmias and CNS stimulation; onset of action of tricyclics may be accelerated. Administration of sertraline in patients stabilized on levothyroxine may result in increased levothyroxine requirements. Ketamine Concurrent use may produce marked hypertension and tachycardia; cautious administration to patients receiving thyroid hormone therapy is recommended. Sympathomimetics Concurrent use may increase the effects of sympathomimetics or thyroid hormone. Thyroid hormones may increase the risk of coronary insufficiency when sympathomimetic agents are administered to patients with coronary artery disease. Drug-Laboratory Test Interactions Changes in thyroxine binding globulin (TBG) concentration must be considered when interpreting levothyroxine and triiodothyronine values, which necessitates measurement and evaluation of unbound (free) hormone and/or determination of the free levothyroxine index. Pregnancy, infectious hepatitis, estrogens, estrogen containing oral contraceptives, and acute intermittent porphyria increase TBG concentrations. Decreases in TBG concentrations are observed in nephrosis, severe hypoproteinemia, severe liver disease, acromegaly, and after androgen or corticosteroid therapy. Familial hyper or hypo thyroxine binding globulinemias have been described, with the incidence of TBG deficiency approximating 1 in 9,000.

SIDE EFFECTS Adverse reactions associated with levothyroxine therapy are primarily those of hyperthyroidism due to therapeutic overdosage (see PRECAUTIONS and OVERDOSAGE). They include the following: General: fatigue, increased appetite, weight loss, heat intolerance, fever, excessive sweating; Central nervous system: headache, hyperactivity, nervousness, anxiety, irritability, emotional lability, insomnia; Musculoskeletal: tremors, muscle weakness; Cardiovascular: palpitations, tachycardia, arrhythmias, increased pulse and blood pressure, heart failure, angina, myocardial infarction, cardiac arrest; Respiratory: dyspnea; Gastrointestinal: diarrhea, vomiting, abdominal cramps and elevations in liver function tests; Dermatologic: hair loss, flushing; Endocrine: decreased bone mineral density; Reproductive: menstrual irregularities, impaired fertility. Pseudotumor cerebri and slipped capital femoral epiphysis have been reported in children receiving levothyroxine therapy. Overtreatment may result in craniosynostosis in infants and premature closure of the epiphyses in children with resultant compromised adult height. Seizures have been reported rarely with the institution of levothyroxine therapy. Inadequate levothyroxine dosage will produce or fail to ameliorate the signs and symptoms of hypothyroidism. Hypersensitivity reactions to inactive ingredients have occurred in patients treated with thyroid hormone products. These include urticaria, pruritus, skin rash, flushing, angioedema, various GI symptoms (abdominal pain, nausea, vomiting and diarrhea), fever, arthralgia, serum sickness and wheezing. Hypersensitivity to levothyroxine itself is not known to occur. DRUG INTERACTIONS Many drugs affect thyroid hormone pharmacokinetics and metabolism (e. g. , absorption, synthesis, secretion, catabolism, protein binding, and target tissue response) and may alter the therapeutic response to LEVOTHROID® (levothyroxine sodium) . In addition, thyroid hormones and thyroid status have varied effects on the pharmacokinetics and actions of other drugs. A listing of drug-thyroidal axis interactions is contained in Table 2. The list of drug-thyroidal axis interactions in Table 2 may not be comprehensive due to the introduction of new drugs that interact with the thyroidal axis or the discovery of previously unknown interactions. The prescriber should be aware of this fact and should consult appropriate reference sources (e. g. , package inserts of newly approved drugs, medical literature) for additional information if a drug-drug interaction with levothyroxine is suspected. Table 2:Drug-Thyroidal Axis Interactions Drugs that may reduce TSH secretion - the reduction is not sustained;therefore,hypothyroidism does not occur Drug or Drug Class Dopamine / Dopamine Agonists Glucocorticoids Octreotide Effect - Use of these agents may result in a transient reduction in TSH secretion when administered at the following doses:Dopamine ( ≥ 1µ g/kg/min); Glucocorticoids (hydrocortisone ≥ 100 mg/day or equivalent);Octreotide ( > 100 µg/day). Drugs that alter thyroid hormone secretion Drugs that may decrease thyroid hormone secretion,which may result in hypothyroidism Drug or Drug Class Aminoglutethimide Iodide Methimazole Amiodarone (including iodine-containing Radiographic contrast agents) Lithium Propylthiouracil (PTU) Sulfonamides Tolbutamide Effect - Long-term lithium therapy can result in goiter in up to 50% of patients, and either subclinical or overt hypothyroidism, each in up to 20% of patients. The fetus, neonate, elderly and euthyroid patients with underlying thyroid disease (e.g., Hashimoto's thyroiditis or with Grave's disease previously treated with radioiodine or surgery) are among those individuals who are particularly susceptible to iodine-induced hypothyroidism. Oral chole-cystographic agents and amiodarone are slowly excreted, producing more prolonged hypothyroidism than parenterally administered iodinated contrast agents. Long-term aminoglutethimide therapy may minimally decrease T4 and T3 levels and increase TSH, although all values remain within normal limits in most patients. Drugs that may increase thyroid hormone secretion,which may result in hyperthyroidism Drug or Drug Class Amiodarone Iodide (including iodine-containing Radiographic contrast agents) Effect - Iodide and drugs that contain pharmacological amounts of iodide may cause hyperthyroidism in euthyroid patients with Grave's disease previously treated with antithyroid drugs or in euthyroid patients with thyroid autonomy (e.g., multinodular goiter or hyperfunctioning thyroid adenoma). Hyperthyroidism may develop over several weeks and may persist for several months after therapy discontinuation.Amiodarone may induce hyper-thyroidism by causing thyroiditis. Drugs that may decrease T4 absorption,which may result in hypothyroidism Drug or Drug Class Antacids Bile Acid Sequestrants Cation Exchange Resins - Aluminum & Magnesium - Cholestyramine - Kayexalate Hydroxides - Colestipol Ferrous Sulfate - Simethicone Calcium Carbonate Sucralfate Effect - Concurrent use may reduce the efficacy of levothyroxine by binding and delaying or preventing absorption, potentially resulting in hypothy-roidism.Calcium carbonate may form an insoluble chelate with levothyroxine, and ferrous sulfate likely forms a ferric-thyroxine complex.Administer levothyroxine at least 4 hours apart from these agents. Drugs that may alter T4 and T3 serum transport - but FT 4 concentration remains normal;and,therefore,the patient remains euthyroid Drugs that may increase serum TBG concentration Clofibrate Estrogens (oral) Mitotane Estrogen-containing Heroin /Methadone Tamoxifen Oral contraceptives 5-Fluorouracil Drugs that may decrease serum TBG concentration Androgens / Anabolic Steroids Glucocorticoids Asparaginase Slow-Release Nicotinic Acid Drugs that may cause protein-binding site displacement Drug or Drug Class Furosemide ( > 80 mg IV) Non Steroidal Anti-Inflammatory Drugs Heparin - Fenamates Hydantoins - Phenylbutazone Salicylates ( > 2 g/day) Effect - Administration of these agents with levothyroxine results in an initial transient increase in FT4.Continued administration results in a decrease in serum T4 and normal FT4 and TSH concentrations and, therefore, patients are clinically euthyroid. Salicylates inhibit binding of T4 and T3 to TBG and transthyretin.An initial increase in serum FT4 is followed by return of FT4 to normal levels with sustained therapeutic serum salicylate concentrations, although total-T4 levels may decrease by as much as 30%. Drugs that may alter T4 and T3 metabolism Drugs that may increase hepatic metabolism,which may result in hypothyroidism Drug or Drug Class Carbamazepine Hydantoins Phenobarbital Rifampin Effect - Stimulation of hepatic microsomal drug-metabolizing enzyme activity may cause increased hepatic degradation of levothyroxine, resulting in increased levothyroxine requirements. Phenytoin and carbamazepine reduce serum protein binding of levothyroxine, and total- and free-T4 may bereduced by 20% to 40%, but most patients have normal serum TSH levels and are clinically euthyroid. Drugs that may decrease T4 5'-deiodinase activity Drug or Drug Class Amiodarone Beta-adrenergic antagonists Glucocorticoids - (e.g., Propranolol > 160 mg/day) - (e.g., Dexamethasone ≥ 4 mg/day) Propylthiouracil (PTU) Effect - Administration of these enzyme inhibitors decreases the peripheral conversion of T4 to T3, leading to decreased T3 levels.However, serum T4 levels are usually normal but may occasionally be slightly increased. In patients treated with large doses of propranolol ( > 160 mg/day), T3 and T4 levels change slightly, TSH levels remain normal, and patients are clinically euthyroid.It should be noted that actions ofparticular beta-adrenergic antagonists may be impaired when the hypothyroid patient is converted to the euthyroid state.Short-term administration of large doses of glucocorticoids may decrease serum T3 concentrations by 30% with minimal change in serum T4 levels.However, long-term glucocor-ticoid therapy may result in slightly decreased T3 and T4 levels due to decreased TBG production (see above). Miscellaneous Drug or Drug Class Anticoagulants (oral) - Coumarin Derivatives - Indandione Derivatives Effect - Thyroid hormones appear to increase the catabolism of vitamin K-dependent clotting factors, thereby increasing the anticoagulant activity of oral anticoagulants. Concomitant use of these agents impairs the compensatory increases in clotting factor synthesis. Prothrombin time should be carefully monitored in patients taking levothyroxine and oral anticoagulants and the dose of anticoagulant therapy adjusted accordingly. Drug or Drug Class Antidepressants - Tricyclics (e.g., Amitriptyline) - Selective Serotonin Reuptake Inhibitors - Tetracyclics (e.g., Maprotiline) (SSRIs;e.g., Sertraline) Effect - Concurrent use of tri/tetracyclic antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines.Toxic effects may include increased risk of cardiac arrhythmias and CNS stimulation;onset of action of tricyclics may be accelerated.Administration of sertraline in patients stabilized on levothyroxine may result in increased levothyroxine requirements. Drug or Drug Class Antidiabetic Agents - Meglitinides - Sulfonylureas - Biguanides - Thiazolidinediones - Insulin Effect - Addition of levothyroxine to antidiabetic or insulin therapy may result in increased antidiabetic agent or insulin requirements.Careful monitoring of diabetic control is recommended, especially when thyroid therapy is started, changed, or discontinued. Drug or Drug Class Cardiac Glycosides Effect - Serum digitalis glycoside levels may be reduced in hyperthyroidism or when the hypothyroid patient is converted to the euthyroid state. Therapeutic effect of digitalis glycosides may be reduced. Drug or Drug Class Cytokines - Interferon-α - Interleukin-2 Effect - Therapy with interferon-α has been associated with the development of antithyroid microsomal antibodies in 20% of patients and some have transient hypothyroidism, hyperthyroidism, or both.Patients who have antithyroid antibodies before treatment are at higher risk for thyroid dysfunction during treatment.Interleukin-2 has been associated with transient painless thyroiditis in 20% of patients.Interferon-β and -γ have not been reported to cause thyroid dysfunction. Drug or Drug Class Growth Hormones - Somatrem - Somatropin Effect - Excessive use of thyroid hormones with growth hormones may accelerate epiphyseal closure. However, untreated hypothyroidism may interfere with growth response to growth hormone. Drug or Drug Class Ketamine Effect - Concurrent use may produce marked hypertension and tachycardia;cautious administration to patients receiving thyroid hormone therapy is recommended. Drug or Drug Class Methylxanthine Bronchodilators - (e.g., Theophylline) Effect - Decreased theophylline clearance may occur in hypothyroid patients; clearance returns to normal when the euthyroid state is achieved. Drug or Drug Class Radiographic Agents Radiographic Agents Effect - Thyroid hormones may reduce the uptake of 123I, 131I, and 99mTc. Drug or Drug Class Sympathomimetics Effect - Concurrent use may increase the effects of sympathomimetics or thyroid hormone.Thyroid hormones may increase the risk of coronary insufficiency when sympathomimetic agents are administered to patients with coronary artery disease. Drug or Drug Class Chloral Hydrate Metoclopramide Perphenazine Diazepam 6-Mercaptopurine Resorcinol Ethionamide Nitroprusside (excessive topical use) Lovastatin Para-aminosalicylate sodium Thiazide Diuretics Effect - These agents have been associated with thyroid hormone and / or TSH level alterations by various mechanisms. Oral anticoagulants Levothyroxine increases the response to oral anticoagulant therapy. Therefore, a decrease in the dose of anticoagulant may be warranted with correction of the hypothyroid state or when the LEVOTHROID® (levothyroxine sodium) dose is increased. Prothrombin time should be closely monitored to permit appropriate and timely dosage adjustments (see Table 2). Digitalis glycosides The therapeutic effects of digitalis glycosides may be reduced by levothyroxine. Serum digitalis glycoside levels may be decreased when a hypothyroid patient becomes euthyroid, necessitating an increase in the dose of digitalis glycosides (see Table 2). Drug-Food Interactions Consumption of certain foods may affect levothyroxine absorption thereby necessitating adjustments in dosing. Soybean flour (infant formula), cotton seed meal, walnuts, and dietary fiber may bind and decrease the absorption of levothyroxine sodium from the GI tract. Drug-Laboratory Test Interactions Changes in TBG concentration must be considered when interpreting T4 and T3 values, which necessitates measurement and evaluation of unbound (free) hormone and/or determination of the free-T4 index (FT4I). Pregnancy, infectious hepatitis, estrogens, estrogen-containing oral contraceptives, and acute intermittent porphyria increase TBG concentrations. Decreases in TBG concentrations are observed in nephrosis, severe hypoproteinemia, severe liver disease, acromegaly, and after androgen or corticosteroid therapy (see also Table 2). Familial hyper- or hypo-thyroxine binding globulinemias have been described, with the incidence of TBG deficiency approximating 1 in 9000.

WARNINGS Warning Thyroid hormones, including UNITHROID, either alone or with other therapeutic agents, should not be used for the treatment of obesity for weight loss. In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines such as those used for their anorectic effects. Levothyroxine sodium should not be used in the treatment of male or female infertility unless this condition is associated with hypothyroidism. In patients with nontoxic diffuse goiter or nodular thyroid disease, particularly the elderly or those with underlying cardiovascular disease, levothyroxine sodium therapy is contraindicated if the serum TSH level is already suppressed due to the risk of precipitating overt thyrotoxicosis (see CONTRAINDICATIONS). If the serum TSH level is not suppressed, UNITHROID should be used with caution in conjunction with careful monitoring of thyroid function for evidence of hyperthyroidism and clinical monitoring for potential associated adverse cardiovascular signs and symptoms of hyperthyroidism. PRECAUTIONS General Levothyroxine has a narrow therapeutic index. Regardless of the indication for use, careful dosage titration is necessary to avoid the consequences of over- or undertreatment. These consequences include, among others, effects on growth and development, cardiovascular function, bone metabolism, reproductive function, cognitive function, emotional state, gastrointestinal function, and on glucose and lipid metabolism. Many drugs interact with levothyroxine sodium necessitating adjustments in dosing to maintain therapeutic response (see DRUG INTERACTIONS). Effects On Bone Mineral Density In women, long-term levothyroxine sodium therapy has been associated with increased bone resorption, thereby decreasing bone mineral density, especially in post-menopausal women on greater than replacement doses or in women who are receiving suppressive doses of levothyroxine sodium. The increased bone resorption may be associated with increased serum levels and urinary excretion of calcium and phosphorous, elevations in bone alkaline phosphatase and suppressed serum parathyroid hormone levels. Therefore, it is recommended that patients receiving levothyroxine sodium be given the minimum dose necessary to achieve the desired clinical and biochemical response. Patients With Underlying Cardiovascular Disease Exercise caution when administering levothyroxine to patients with cardiovascular disorders and to the elderly in whom there is an increased risk of occult cardiac disease. In these patients, levothyroxine therapy should be initiated at lower doses than those recommended in younger individuals or in patients without cardiac disease (see WARNINGS; PRECAUTIONS, Geriatric Use; and DOSAGE AND ADMINISTRATION). If cardiac symptoms develop or worsen, the levothyroxine dose should be reduced or withheld for one week and then cautiously restarted at a lower dose. Overtreatment with levothyroxine sodium may have adverse cardiovascular effects such as an increase in heart rate, cardiac wall thickness, and cardiac contractility and may precipitate angina or arrhythmias. Patients with coronary artery disease who are receiving levothyroxine therapy should be monitored closely during surgical procedures, since the possibility of precipitating cardiac arrhythmias may be greater in those treated with levothyroxine. Concomitant administration of levothyroxine and sympathomimetic agents to patients with coronary artery disease may precipitate coronary insufficiency. Patients With Nontoxic Diffuse Goiter Or Nodular Thyroid Disease Exercise caution when administering levothyroxine to patients with nontoxic diffuse goiter or nodular thyroid disease in order to prevent precipitation of thyrotoxicosis (see WARNINGS). If the serum TSH is already suppressed, levothyroxine sodium should not be administered (see CONTRAINDICATIONS). Associated Endocrine Disorders Hypothalamic/Pituitary Hormone Deficiencies In patients with secondary or tertiary hypothyroidism, additional hypothalamic/pituitary hormone deficiencies should be considered, and, if diagnosed, treated (see PRECAUTIONS, Autoimmune polyglandular syndrome for adrenal insufficiency). Autoimmune Polyglandular Syndrome Occasionally, chronic autoimmune thyroiditis may occur in association with other autoimmune disorders such as adrenal insufficiency, pernicious anemia, and insulin-dependent diabetes mellitus. Patients with concomitant adrenal insufficiency should be treated with replacement glucocorticoids prior to initiation of treatment with levothyroxine sodium. Failure to do so may precipitate an acute adrenal crisis when thyroid hormone therapy is initiated, due to increased metabolic clearance of glucocorticoids by thyroid hormone. Patients with diabetes mellitus may require upward adjustments of their antidiabetic therapeutic regimens when treated with levothyroxine (see PRECAUTIONS: DRUG INTERACTIONS). Other Associated Medical Conditions Infants with congenital hypothyroidism appear to be at increased risk for other congenital anomalies, with cardiovascular anomalies (pulmonary stenosis, atrial septal defect, and ventricular septal defect,) being the most common association. Laboratory Tests General The diagnosis of hypothyroidism is confirmed by measuring TSH levels using a sensitive assay (second generation assay sensitivity ≤ 0.1 mlU/L or third generation assay sensitivity ≤ 0.01 mlU/L) and measurement of free-T4. The adequacy of therapy is determined by periodic assessment of appropriate laboratory tests and clinical evaluation. The choice of laboratory tests depends on various factors including the etiology of the underlying thyroid disease, the presence of concomitant medical conditions, including pregnancy, and the use of concomitant medications (see PRECAUTIONS: DRUG INTERACTIONS and Drug-Laboratory Test Interactions). Persistent clinical and laboratory evidence of hypothyroidism despite an apparent adequate replacement dose of UNITHROID may be evidence of inadequate absorption, poor compliance, drug interactions, or decreased T4 potency of the drug product. Adults In adult patients with primary (thyroidal) hypothyroidism, serum TSH levels (using a sensitive assay) alone may be used to monitor therapy. The frequency of TSH monitoring during levothyroxine dose titration depends on the clinical situation but it is generally recommended at 6-8 week intervals until normalization. For patients who have recently initiated levothyroxine therapy and whose serum TSH has normalized or in patients who have had their dosage of levothyroxine changed, the serum TSH concentration should be measured after 8-12 weeks. When the optimum replacement dose has been attained, clinical (physical examination) and biochemical monitoring may be performed every 6-12 months, depending on the clinical situation, and whenever there is a change in the patient's status. It is recommended that a physical examination and a serum TSH measurement be performed at least annually in patients receiving UNITHROID. (see WARNINGS, PRECAUTIONS and DOSAGE AND ADMINISTRATION). Pediatrics In patients with congenital hypothyroidism, the adequacy of replacement therapy should be assessed by measuring both serum TSH (using a sensitive assay) and totalor free-T4. During the first three years of life, the serum total- or free-T4 should be maintained at all times in the upper half of the normal range. While the aim of therapy is to also normalize the serum TSH level, this is not always possible in a small percentage of patients, particularly in the first few months of therapy. TSH may not normalize due to a resetting of the pituitary-thyroid feedback threshold as a result of in utero hypothyroidism. Failure of the serum T4 to increase into the upper half of the normal range within 2 weeks of initiation of UNITHROID therapy and/or of the serum TSH to decrease below 20 mU/L within 4 weeks should alert the physician to the possibility that the child is not receiving adequate therapy. Careful inquiry should then be made regarding compliance, dose of medication administered, and method of administration prior to raising the dose of UNlTHROID. The recommended frequency of monitoring of TSH and total or free T4 in children is as follows: at 2 and 4 weeks after the initiation of treatment; every 1-2 months during the first year of life; every 2-3 months between 1 and 3 years of age; and every 3 to 12 months thereafter until growth is completed. More frequent intervals of monitoring may be necessary if poor compliance is suspected or abnormal values are obtained. It is recommended that TSH and T4 levels, and a physical examination, if indicated, be performed 2 weeks after any change in UNITHROID dosage. Routine clinical examination, including assessment of mental and physical growth and development, and bone maturation should be performed at regular intervals (see PRECAUTIONS, Pediatric Use and DOSAGE AND ADMINISTRATION). Secondary (pituitary) And Tertiary (hypothalamic) Hypothyroidism Adequacy of therapy should be assessed by measuring serum free-T4 levels, which should be maintained in the upper half of the normal range in these patients. Carcinogenesis, Mutagenesis, And Impairment Of Fertility Animal studies have not been performed to evaluate the carcinogenic potential, mutagenic potential or effects on fertility of levothyroxine. The synthetic T4 in UNITHROID is identical to that produced naturally by the human thyroid gland. Although there has been a reported association between prolonged thyroid hormone therapy and breast cancer, this has not been confirmed. Patients receiving UNITHROID for appropriate clinical indications should be titrated to the lowest effective replacement dose. Pregnancy Category A - Studies in women taking levothyroxine sodium during pregnancy have not shown an increased risk of congenital abnormalities. Therefore, the possibility of fetal harm appears remote. UNITHROID should not be discontinued during pregnancy and hypothyroidism diagnosed during pregnancy should be promptly treated. Hypothyroidism during pregnancy is associated with a higher rate of complications, including spontaneous abortion, pre-eclampsia, stillbirth and premature delivery. Maternal hypothyroidism may have an adverse effect on fetal and childhood growth and development. During pregnancy, serum T4 levels may decrease and serum TSH levels increase to values outside the normal range. Since elevations in serum TSH may occur as early as 4 weeks gestation, pregnant women taking UNITHROID should have their TSH measured during each trimester. An elevated serum TSH level should be corrected by an increase in the dose of UNITHROID. Since postpartum TSH levels are similar to preconception values, the UNITHROID dosage should return to the pre-pregnancy dose immediately after delivery. A serum TSH level should be obtained 6-8 weeks postpartum. Thyroid hormones cross the placental barrier to some extent as evidenced by levels in cord blood of athyroceotic fetuses being approximately one third maternal levels. Transfer of thyroid hormone from the mother to the fetus, however, may not be adequate to prevent in utero, hypothyroidism. Nursing Mothers Although thyroid hormones are excreted only minimally in human milk, caution should be exercised when UNITHROID is administered to a nursing woman. However, adequate replacement doses of levothyroxine are generally needed to maintain normal lactation. Pediatric Use General The goal of treatment in pediatric patients with hypothyroidism is to achieve and maintain normal intellectual and physical growth and development. The initial dose of levothyroxine varies with age and body weight (see DOSAGE AND ADMINISTRATION, Table 3). Dosing adjustments are based on an assessment of the individual patient's clinical and laboratory parameters (see PRECAUTIONS, Laboratory Tests). In children in whom a diagnosis of permanent hypothyroidism has not been established, it is recommended that levothyroxine administration be discontinued for a 30-day trial period, but only after the child is at least 3 years of age. Serum T4 and TSH levels should then be obtained. If the T4 is low and the TSH high, the diagnosis of permanent hypothyroidism is established, and levothyroxine therapy should be reinstituted. If the T4 and TSH levels are normal, euthyroidism may be assumed and, therefore, the hypothyroidism can be considered to have been transient. In this instance, however, the physician should carefully monitor the child and repeat the thyroid function tests if any signs or symptoms of hypothyroidism develop. In this setting, the clinician should have a high index of suspicion of relapse. If the results of the levothyroxine withdrawal test are inconclusive, careful follow-up and subsequent testing will be necessary. Since some more severely affected children may become clinically hypothyroid when treatment is discontinued for 30 days, an alternate approach is to reduce the replacement dose of levothyroxine by half during the 30-day trial period. If, after 30 days, the serum TSH is elevated above 20 mU/L, the diagnosis of permanent hypothyroidism is confirmed, and full replacement therapy should be resumed. However, if the serum TSH has not risen to greater than 20 mU/L, levothyroxine treatment should be discontinued for another 30-day trial period followed by repeat serum T4 and TSH. The presence of concomitant medical conditions should be considered in certain clinical circumstances and, if present, appropriately treated (see PRECAUTIONS). Congenital Hypothyroidism (see PRECAUTIONS, Laboratory Tests and DOSAGE AND ADMINISTRATION) Rapid restoration of normal serum T4 concentrations is essential for preventing the adverse effects of congenital hypothyroidism on intellectual development as well as on overall physical growth and maturation. Therefore, UNITHROID therapy should be initiated immediately upon diagnosis and is generally continued for life. During the first 2 weeks of UNITHROID therapy, infants should be closely monitored for cardiac overload, arrhythmias, and aspiration from avid suckling. The patient should be monitored closely to avoid undertreatment or overtreatment. Undertreatment may have deleterious effects on intellectual development and linear growth. Overtreatment has been associated with craniosynostosis in infants, and may adversely affect the tempo of brain maturation and accelerate the bone age with resultant premature closure of the epiphyses and compromised adult stature. Acquired Hypothyroidism In Pediatric Patients The patient should be monitored closely to avoid undertreatment and overtreatment. Undertreatment may result in poor school performance due to impaired concentration and slowed mentation and in reduced adult height. Overtreatment may accelerate the bone age and result in premature epiphyseal closure and compromised adult stature. Treated children may manifest a period of catch-up growth, which may be adequate in some cases to normalize adult height. In children with severe or prolonged hypothyroidism, catch-up growth may not be adequate to normalize adult height. Geriatric Use Because of the increased prevalence of cardiovascular disease among the elderly, levothyroxine therapy should not be initiated at the full replacement dose (see WARNINGS, PRECAUTIONS and DOSAGE AND ADMINISTRATION).

WARNINGS Levothyroxine sodium should not be used in the treatment of male or female infertility unless this condition is associated with hypothyroidism. In patients with nontoxic diffuse goiter or nodular thyroid disease, particularly the elderly or those with underlying cardiovascular disease, levothyroxine sodium therapy is contraindicated if the serum TSH level is already suppressed due to the risk of precipitating overt thyrotoxicosis (see CONTRAINDICATIONS). If the serum TSH level is not suppressed, SYNTHROID should be used with caution in conjunction with careful monitoring of thyroid function for evidence of hyperthyroidism and clinical monitoring for potential associated adverse cardiovascular signs and symptoms of hyperthyroidism. PRECAUTIONS General Levothyroxine has a narrow therapeutic index. Regardless of the indication for use, careful dosage titration is necessary to avoid the consequences of over- or under-treatment. These consequences include, among others, effects on growth and development, cardiovascular function, bone metabolism, reproductive function, cognitive function, emotional state, gastrointestinal function, and on glucose and lipid metabolism. Many drugs interact with levothyroxine sodium necessitating adjustments in dosing to maintain therapeutic response (see DRUG INTERACTIONS ). Effects On Bone Mineral Density In women, long-term levothyroxine sodium therapy has been associated with increased bone resorption, thereby decreasing bone mineral density, especially in post-menopausal women on greater than replacement doses or in women who are receiving suppressive doses of levothyroxine sodium. The increased bone resorption may be associated with increased serum levels and urinary excretion of calcium and phosphorous, elevations in bone alkaline phosphatase and suppressed serum parathyroid hormone levels. Therefore, it is recommended that patients receiving levothyroxine sodium be given the minimum dose necessary to achieve the desired clinical and biochemical response. Patients With Underlying Cardiovascular Disease Exercise caution when administering levothyroxine to patients with cardiovascular disorders and to the elderly in whom there is an increased risk of occult cardiac disease. In these patients, levothyroxine therapy should be initiated at lower doses than those recommended in younger individuals or in patients without cardiac disease (see WARNINGS, PRECAUTIONS - Geriatric Use, and DOSAGE AND ADMINISTRATION). If cardiac symptoms develop or worsen, the levothyroxine dose should be reduced or withheld for one week and then cautiously restarted at a lower dose. Overtreatment with levothyroxine sodium may have adverse cardiovascular effects such as an increase in heart rate, cardiac wall thickness, and cardiac contractility and may precipitate angina or arrhythmias. Patients with coronary artery disease who are receiving levothyroxine therapy should be monitored closely during surgical procedures, since the possibility of precipitating cardiac arrhythmias may be greater in those treated with levothyroxine. Concomitant administration of levothyroxine and sympathomimetic agents to patients with coronary artery disease may precipitate coronary insufficiency. Patients With Nontoxic Diffuse Goiter Or Nodular Thyroid Disease Exercise caution when administering levothyroxine to patients with nontoxic diffuse goiter or nodular thyroid disease in order to prevent precipitation of thyrotoxicosis (see WARNINGS). If the serum TSH is already suppressed, levothyroxine sodium should not be administered (see CONTRAINDICATIONS). Associated Endocrine Disorders Hypothalamic/Pituitary Hormone Deficiencies In patients with secondary or tertiary hypothyroidism, additional hypothalamic/pituitary hormone deficiencies should be considered, and, if diagnosed, treated (see PRECAUTIONS - Autoimmune polyglandular syndrome for adrenal insufficiency). Autoimmune Polyglandular Syndrome Occasionally, chronic autoimmune thyroiditis may occur in association with other autoimmune disorders such as adrenal insufficiency, pernicious anemia, and insulin-dependent diabetes mellitus. Patients with concomitant adrenal insufficiency should be treated with replacement glucocorticoids prior to initiation of treatment with levothyroxine sodium. Failure to do so may precipitate an acute adrenal crisis when thyroid hormone therapy is initiated, due to increased metabolic clearance of glucocorticoids by thyroid hormone. Patients with diabetes mellitus may require upward adjustments of their antidiabetic therapeutic regimens when treated with levothyroxine (see DRUG INTERACTIONS). Other Associated Medical Conditions Infants with congenital hypothyroidism appear to be at increased risk for other congenital anomalies, with cardiovascular anomalies (pulmonary stenosis, atrial septal defect, and ventricular septal defect) being the most common association. Laboratory Tests General The diagnosis of hypothyroidism is confirmed by measuring TSH levels using a sensitive assay (second generation assay sensitivity ≤ 0.1 mIU/L or third generation assay sensitivity ≤ 0.01 mIU/L) and measurement of free-T4. The adequacy of therapy is determined by periodic assessment of appropriate laboratory tests and clinical evaluation. The choice of laboratory tests depends on various factors including the etiology of the underlying thyroid disease, the presence of concomitant medical conditions, including pregnancy, and the use of concomitant medications (see DRUG INTERACTIONS and Drug- Laboratory Test Interactions). Persistent clinical and laboratory evidence of hypothyroidism despite an apparent adequate replacement dose of SYNTHROID may be evidence of inadequate absorption, poor compliance, drug interactions, or decreased T4 potency of the drug product. Adults In adult patients with primary (thyroidal) hypothyroidism, serum TSH levels (using a sensitive assay) alone may be used to monitor therapy. The frequency of TSH monitoring during levothyroxine dose titration depends on the clinical situation but it is generally recommended at 6-8 week intervals until normalization. For patients who have recently initiated levothyroxine therapy and whose serum TSH has normalized or in patients who have had their dosage or brand of levothyroxine changed, the serum TSH concentration should be measured after 8-12 weeks. When the optimum replacement dose has been attained, clinical (physical examination) and biochemical monitoring may be performed every 6-12 months, depending on the clinical situation, and whenever there is a change in the patient's status. It is recommended that a physical examination and a serum TSH measurement be performed at least annually in patients receiving SYNTHROID (see WARNINGS, PRECAUTIONS, and DOSAGE AND ADMINISTRATION). Pediatrics In patients with congenital hypothyroidism, the adequacy of replacement therapy should be assessed by measuring both serum TSH (using a sensitive assay) and total- or free- T4. During the first three years of life, the serum total- or free- T should be maintained at all times in the upper half of the normal range. While the aim of therapy is to also normalize the serum TSH level, this is not always possible in a small percentage of patients, particularly in the first few months of therapy. TSH may not normalize due to a resetting of the pituitary-thyroid feedback threshold as a result of in utero hypothyroidism. Failure of the serum T to increase into the upper half of the normal range within 2 weeks of initiation of SYNTHROID therapy and/or of the serum TSH to decrease below 20 mU/L within 4 weeks should alert the physician to the possibility that the child is not receiving adequate therapy. Careful inquiry should then be made regarding compliance, dose of medication administered, and method of administration prior to raising the dose of SYNTHROID. The recommended frequency of monitoring of TSH and total or free T4 in children is as follows: at 2 and 4 weeks after the initiation of treatment; every 1-2 months during the first year of life; every 2-3 months between 1 and 3 years of age; and every 3 to 12 months thereafter until growth is completed. More frequent intervals of monitoring may be necessary if poor compliance is suspected or abnormal values are obtained. It is recommended that TSH and T4 levels, and a physical examination, if indicated, be performed 2 weeks after any change in SYNTHROID dosage. Routine clinical examination, including assessment of mental and physical growth and development, and bone maturation, should be performed at regular intervals (see PRECAUTIONS - Pediatric Use and DOSAGE AND ADMINISTRATION). Secondary (Pituitary) and Tertiary (Hypothalamic) Hypothyroidism Adequacy of therapy should be assessed by measuring serum free- T4 levels, which should be maintained in the upper half of the normal range in these patients. Drug-Food Interactions Consumption of certain foods may affect levothyroxine absorption thereby necessitating adjustments in dosing. Soybean flour (infant formula), cotton seed meal, walnuts, and dietary fiber may bind and decrease the absorption of levothyroxine sodium from the GI tract. Drug-Laboratory Test Interactions Changes in TBG concentration must be considered when interpreting T4 and T3 values, which necessitates measurement and evaluation of unbound (free) hormone and/or determination of the free T4 index (FT4I). Pregnancy, infectious hepatitis, estrogens, estrogen-containing oral contraceptives, and acute intermittent porphyria increase TBG concentrations. Decreases in TBG concentrations are observed in nephrosis, severe hypoproteinemia, severe liver disease, acromegaly, and after androgen or corticosteroid therapy (see also Table 2). Familial hyper- or hypo-thyroxine binding globulinemias have been described, with the incidence of TBG deficiency approximating 1 in 9000. Carcinogenesis, Mutagenesis, And Impairment Of Fertility Animal studies have not been performed to evaluate the carcinogenic potential, mutagenic potential or effects on fertility of levothyroxine. The synthetic T4 in SYNTHROID is identical to that produced naturally by the human thyroid gland. Although there has been a reported association between prolonged thyroid hormone therapy and breast cancer, this has not been confirmed. Patients receiving SYNTHROID for appropriate clinical indications should be titrated to the lowest effective replacement dose. Pregnancy Category A Studies in women taking levothyroxine sodium during pregnancy have not shown an increased risk of congenital abnormalities. Therefore, the possibility of fetal harm appears remote. SYNTHROID should not be discontinued during pregnancy and hypothyroidism diagnosed during pregnancy should be promptly treated. Hypothyroidism during pregnancy is associated with a higher rate of complications, including spontaneous abortion, pre-eclampsia, stillbirth and premature delivery. Maternal hypothyroidism may have an adverse effect on fetal and childhood growth and development. During pregnancy, serum T4 levels may decrease and serum TSH levels increase to values outside the normal range. Since elevations in serum TSH may occur as early as 4 weeks gestation, pregnant women taking SYNTHROID should have their TSH measured during each trimester. An elevated serum TSH level should be corrected by an increase in the dose of SYNTHROID. Since postpartum TSH levels are similar to preconception values, the SYNTHROID dosage should return to the pre-pregnancy dose immediately after delivery. A serum TSH level should be obtained 6-8 weeks postpartum. Thyroid hormones cross the placental barrier to some extent as evidenced by levels in cord blood of athyreotic fetuses being approximately one-third maternal levels. Transfer of thyroid hormone from the mother to the fetus, however, may not be adequate to prevent in utero hypothyroidism. Nursing Mothers Although thyroid hormones are excreted only minimally in human milk, caution should be exercised when SYNTHROID is administered to a nursing woman. However, adequate replacement doses of levothyroxine are generally needed to maintain normal lactation. Pediatric Use General The goal of treatment in pediatric patients with hypothyroidism is to achieve and maintain normal intellectual and physical growth and development. The initial dose of levothyroxine varies with age and body weight (see DOSAGE AND ADMINISTRATION - Table 3). Dosing adjustments are based on an assessment of the individual patient's clinical and laboratory parameters (see PRECAUTIONS - Laboratory Tests). In children in whom a diagnosis of permanent hypothyroidism has not been established, it is recommended that levothyroxine administration be discontinued for a 30-day trial period, but only after the child is at least 3 years of age. Serum T4 and TSH levels should then be obtained. If the T4 is low and the TSH high, the diagnosis of permanent hypothyroidism is established, and levothyroxine therapy should be reinstituted. If the T4 and TSH levels are normal, euthyroidism may be assumed and, therefore, the hypothyroidism can be considered to have been transient. In this instance, however, the physician should carefully monitor the child and repeat the thyroid function tests if any signs or symptoms of hypothyroidism develop. In this setting, the clinician should have a high index of suspicion of relapse. If the results of the levothyroxine withdrawal test are inconclusive, careful follow-up and subsequent testing will be necessary. Since some more severely affected children may become clinically hypothyroid when treatment is discontinued for 30 days, an alternate approach is to reduce the replacement dose of levothyroxine by half during the 30-day trial period. If, after 30 days, the serum TSH is elevated above 20 mU/L, the diagnosis of permanent hypothyroidism is confirmed, and full replacement therapy should be resumed. However, if the serum TSH has not risen to greater than 20 mU/L, levothyroxine treatment should be discontinued for another 30-day trial period followed by repeat serum T4 and TSH testing. The presence of concomitant medical conditions should be considered in certain clinical circumstances and, if present, appropriately treated (see PRECAUTIONS). Congenital Hypothyroidism (see PRECAUTIONS - Laboratory Tests and DOSAGE AND ADMINISTRATION) Rapid restoration of normal serum T4 concentrations is essential for preventing the adverse effects of congenital hypothyroidism on intellectual development as well as on overall physical growth and maturation. Therefore, SYNTHROID therapy should be initiated immediately upon diagnosis and is generally continued for life. During the first 2 weeks of SYNTHROID therapy, infants should be closely monitored for cardiac overload, arrhythmias, and aspiration from avid suckling. The patient should be monitored closely to avoid undertreatment or overtreatment. Undertreatment may have deleterious effects on intellectual development and linear growth. Overtreatment has been associated with craniosynostosis in infants, and may adversely affect the tempo of brain maturation and accelerate the bone age with resultant premature closure of the epiphyses and compromised adult stature. Acquired Hypothyroidism In Pediatric Patients The patient should be monitored closely to avoid undertreatment and overtreatment. Undertreatment may result in poor school performance due to impaired concentration and slowed mentation and in reduced adult height. Overtreatment may accelerate the bone age and result in premature epiphyseal closure and compromised adult stature. Treated children may manifest a period of catch-up growth, which may be adequate in some cases to normalize adult height. In children with severe or prolonged hypothyroidism, catch-up growth may not be adequate to normalize adult height. Geriatric Use Because of the increased prevalence of cardiovascular disease among the elderly, levothyroxine therapy should not be initiated at the full replacement dose (see WARNINGS, PRECAUTIONS, and DOSAGE AND ADMINISTRATION).

WARNINGS WARNING Thyroid hormones, including LEVOXYL, either alone or with other therapeutic agents, should not be used for the treatment of obesity or for weight loss. In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines such as those used for their anorectic effects. Levothyroxine sodium should not be used in the treatment of male or female infertility unless this condition is associated with hypothyroidism. In patients with nontoxic diffuse goiter or nodular thyroid disease, particularly the elderly or those with underlying cardiovascular disease, levothyroxine sodium therapy is contraindicated if the serum TSH level is already suppressed due to the risk of precipitating overt thyrotoxicosis (see CONTRAINDICATIONS). If the serum TSH level is not suppressed, LEVOXYL should be used with caution in conjunction with careful monitoring of thyroid function for evidence of hyperthyroidism and clinical monitoring for potential associated adverse cardiovascular signs and symptoms of hyperthyroidism. PRECAUTIONS General Levothyroxine has a narrow therapeutic index. Regardless of the indication for use, careful dosage titration is necessary to avoid the consequences of over- or under-treatment. These consequences include, among others, effects on growth and development, cardiovascular function, bone metabolism, reproductive function, cognitive function, emotional state, gastrointestinal function, and on glucose and lipid metabolism. Many drugs interact with levothyroxine sodium necessitating adjustments in dosing to maintain therapeutic response (see DRUG INTERACTIONS). Effects On Bone Mineral Density In women, long-term levothyroxine sodium therapy has been associated with decreased bone mineral density, especially in postmenopausal women on greater than replacement doses or in women who are receiving suppressive doses of levothyroxine sodium. Therefore, it is recommended that patients receiving levothyroxine sodium be given the minimum dose necessary to achieve the desired clinical and biochemical response. Patients With Underlying Cardiovascular Disease Exercise caution when administering levothyroxine to patients with cardiovascular disorders and to the elderly in whom there is an increased risk of occult cardiac disease. In these patients, levothyroxine therapy should be initiated at lower doses than those recommended in younger individuals or in patients without cardiac disease (see WARNINGS; PRECAUTIONS, Geriatric Use; and DOSAGE AND ADMINISTRATION ). If cardiac symptoms develop or worsen, the levothyroxine dose should be reduced or withheld for one week and then cautiously restarted at a lower dose. Overtreatment with levothyroxine sodium may have adverse cardiovascular effects such as an increase in heart rate, cardiac wall thickness, and cardiac contractility and may precipitate angina or arrhythmias. Patients with coronary artery disease who are receiving levothyroxine therapy should be monitored closely during surgical procedures, since the possibility of precipitating cardiac arrhythmias may be greater in those treated with levothyroxine. Concomitant administration of levothyroxine and sympathomimetic agents to patients with coronary artery disease may precipitate coronary insufficiency. Patients With Nontoxic Diffuse Goiter Or Nodular Thyroid Disease Exercise caution when administering levothyroxine to patients with nontoxic diffuse goiter or nodular thyroid disease in order to prevent precipitation of thyrotoxicosis (see WARNINGS ). If the serum TSH is already suppressed, levothyroxine sodium should not be administered (see CONTRAINDICATIONS). Associated Endocrine disorders Hypothalamic/Pituitary Hormone Deficiencies In patients with secondary or tertiary hypothyroidism, additional hypothalamic/pituitary hormone deficiencies should be considered, and, if diagnosed, treated (see PRECAUTIONS, Autoimmune polyglandular syndrome) for adrenal insufficiency. Autoimmune Polyglandular Syndrome Occasionally, chronic autoimmune thyroiditis may occur in association with other autoimmune disorders such as adrenal insufficiency, pernicious anemia, and insulin-dependent diabetes mellitus. Patients with concomitant adrenal insufficiency should be treated with replacement glucocorticoids prior to initiation of treatment with levothyroxine sodium. Failure to do so may precipitate an acute adrenal crisis when thyroid hormone therapy is initiated, due to increased metabolic clearance of glucocorticoids by thyroid hormone. Patients with diabetes mellitus may require upward adjustments of their antidiabetic therapeutic regimens when treated with levothyroxine (see PRECAUTIONS, DRUG INTERACTIONS). Other Associated Medical Conditions Infants with congenital hypothyroidism appear to be at increased risk for other congenital anomalies, with cardiovascular anomalies (pulmonary stenosis, atrial septal defect, and ventricular septal defect,) being the most common association. Laboratory Tests General The diagnosis of hypothyroidism is confirmed by measuring TSH levels using a sensitive assay (second generation assay sensitivity ≤0.1 mIU/L or third generation assay sensitivity ≤0.01 mIU/L) and measurement of free-T4. The adequacy of therapy is determined by periodic assessment of appropriate laboratory tests and clinical evaluation. The choice of laboratory tests depends on various factors including the etiology of the underlying thyroid disease, the presence of concomitant medical conditions, including pregnancy, and the use of concomitant medications (see PRECAUTIONS, DRUG INTERACTIONS and Drug- Laboratory Test Interactions). Persistent clinical and laboratory evidence of hypothyroidism despite an apparent adequate replacement dose of LEVOXYL may be evidence of inadequate absorption, poor compliance, drug interactions, or decreased T4 potency of the drug product. Adults In adult patients with primary (thyroidal) hypothyroidism, serum TSH levels (using a sensitive assay) alone may be used to monitor therapy. The frequency of TSH monitoring during levothyroxine dose titration depends on the clinical situation but it is generally recommended at 6 - 8 week intervals until normalization. For patients who have recently initiated levothyroxine therapy and whose serum TSH has normalized or in patients who have had their dosage or brand of levothyroxine changed, the serum TSH concentration should be measured after 8 - 12 weeks. When the optimum replacement dose has been attained, clinical (physical examination) and biochemical monitoring may be performed every 6 - 12 months, depending on the clinical situation, and whenever there is a change in the patient's status. It is recommended that a physical examination and a serum TSH measurement be performed at least annually in patients receiving LEVOXYL (see WARNINGS , PRECAUTIONS, and DOSAGE AND ADMINISTRATION ). Pediatrics In patients with congenital hypothyroidism, the adequacy of replacement therapy should be assessed by measuring both serum TSH (using a sensitive assay) and total- or free- T4. During the first three years of life, the serum total- or free- T4 should be maintained at all times in the upper half of the normal range. While the aim of therapy is to also normalize the serum TSH level, this is not always possible in a small percentage of patients, particularly in the first few months of therapy. TSH may not normalize due to a resetting of the pituitary-thyroid feedback threshold as a result of in utero hypothyroidism. Failure of the serum T to increase into the upper half of the normal range within 2 weeks of initiation of LEVOXYL therapy and/or of the serum TSH to decrease below 20 mU/L within 4 weeks should alert the physician to the possibility that the child is not receiving adequate therapy. Careful inquiry should then be made regarding compliance, dose of medication administered, and method of administration prior to raising the dose of LEVOXYL. The recommended frequency of monitoring of TSH and total or free T4 in children is as follows: at 2 and 4 weeks after the initiation of treatment; every 1 - 2 months during the first year of life; every 2 - 3 months between 1 and 3 years of age; and every 3 to 12 months thereafter until growth is completed. More frequent intervals of monitoring may be necessary if poor compliance is suspected or abnormal values are obtained. It is recommended that TSH and T4 levels, and a physical examination, if indicated, be performed 2 weeks after any change in LEVOXYL dosage. Routine clinical examination, including assessment of mental and physical growth and development, and bone maturation, should be performed at regular intervals (see PRECAUTIONS, Pediatric Use and DOSAGE AND ADMINISTRATION). Secondary (Pituitary) And Tertiary (Hypothalamic) Hypothyroidism Adequacy of therapy should be assessed by measuring serum free-T4 levels ,which should be maintained in the upper half of the normal range in these patients. Drug-Food Interactions Consumption of certain foods may affect levothyroxine absorption thereby necessitating adjustments in dosing. Soybean flour (infant formula), cotton seed meal, walnuts, and dietary fiber may bind and decrease the absorption of levothyroxine sodium from the GI tract. Drug-Laboratory Test Interactions Changes in TBG concentration must be considered when interpreting T4 and T3 values, which necessitates measurement and evaluation of unbound (free) hormone and/or determination of the free T4 index (FT4I). Pregnancy, infectious hepatitis, estrogens, estrogen-containing oral contraceptives, and acute intermittent porphyria increase TBG concentrations. Decreases in TBG concentrations are observed in nephrosis, severe hypoproteinemia, severe liver disease, acromegaly, and after androgen or corticosteroid therapy (see also Table 2). Familial hyper- or hypo-thyroxine binding globulinemias have been described, with the incidence of TBG deficiency approximating 1 in 9000. Carcinogenesis, Mutagenesis, And Impairment Of Fertility Animal studies have not been performed to evaluate the carcinogenic potential, mutagenic potential or effects on fertility of levothyroxine. The synthetic T4 in LEVOXYL is identical to that produced naturally by the human thyroid gland. Although there has been a reported association between prolonged thyroid hormone therapy and breast cancer, this has not been confirmed. Patients receiving LEVOXYL for appropriate clinical indications should be titrated to the lowest effective replacement dose. Pregnancy Category A Studies in women taking levothyroxine sodium during pregnancy have not shown an increased risk of congenital abnormalities. Therefore, the possibility of fetal harm appears remote. LEVOXYL should not be discontinued during pregnancy and hypothyroidism diagnosed during pregnancy should be promptly treated. Hypothyroidism during pregnancy is associated with a higher rate of complications, including spontaneous abortion, pre-eclampsia, stillbirth and premature delivery. Maternal hypothyroidism may have an adverse effect on fetal and childhood growth and development. During pregnancy, serum T4 levels may decrease and serum TSH levels increase to values outside the normal range. Since elevations in serum TSH may occur as early as 4 weeks gestation, pregnant women taking LEVOXYL should have their TSH measured during each trimester. An elevated serum TSH level should be corrected by an increase in the dose of LEVOXYL. Since postpartum TSH levels are similar to preconception values, the LEVOXYL dosage should return to the pre-pregnancy dose immediately after delivery. A serum TSH level should be obtained 6 - 8 weeks postpartum. Thyroid hormones do not readily cross the placental barrier; however, some transfer does occur as evidenced by levels in cord blood of athyreotic fetuses being approximately one-third maternal levels. Transfer of thyroid hormone from the mother to the fetus, however, may not be adequate to prevent in utero hypothyroidism. Nursing Mothers Although thyroid hormones are excreted only minimally in human milk, caution should be exercised when LEVOXYL is administered to a nursing woman. However, adequate replacement doses of levothyroxine are generally needed to maintain normal lactation. Pediatric Use General The goal of treatment in pediatric patients with hypothyroidism is to achieve and maintain normal intellectual and physical growth and development. The initial dose of levothyroxine varies with age and body weight (see DOSAGE AND ADMINISTRATION, Table 3). Dosing adjustments are based on an assessment of the individual patient's clinical and laboratory parameters (see PRECAUTIONS, Laboratory Tests). In children in whom a diagnosis of permanent hypothyroidism has not been established, it is recommended that levothyroxine administration be discontinued for a 30-day trial period, but only after the child is at least 3 years of age. Serum T4 and TSH levels should then be obtained. If the T4 is low and the TSH high, the diagnosis of permanent hypothyroidism is established, and levothyroxine therapy should be reinstituted. If the T4 and TSH levels are normal, euthyroidism may be assumed and, therefore, the hypothyroidism can be considered to have been transient. In this instance, however, the physician should carefully monitor the child and repeat the thyroid function tests if any signs or symptoms of hypothyroidism develop. In this setting, the clinician should have a high index of suspicion of relapse. If the results of the levothyroxine withdrawal test are inconclusive, careful follow-up and subsequent testing will be necessary. Since some more severely affected children may become clinically hypothyroid when treatment is discontinued for 30 days, an alternate approach is to reduce the replacement dose of levothyroxine by half during the 30-day trial period. If, after 30 days, the serum TSH is elevated above 20 mU/L, the diagnosis of permanent hypothyroidism is confirmed, and full replacement therapy should be resumed. However, if the serum TSH has not risen to greater than 20mU/L, levothyroxine treatment should be discontinued for another 30-day trial period followed by repeat serum T4 and TSH. The presence of concomitant medical conditions should be considered in certain clinical circumstances and, if present, appropriately treated (see PRECAUTIONS). Congenital Hypothyroidism (see PRECAUTIONS, Laboratory Tests and DOSAGE AND ADMINISTRATION) Rapid restoration of normal serum T4 concentrations is essential for preventing the adverse effects of congenital hypothyroidism on intellectual development as well as on overall physical growth and maturation. Therefore, LEVOXYL therapy should be initiated immediately upon diagnosis and is generally continued for life. During the first 2 weeks of LEVOXYL therapy, infants should be closely monitored for cardiac overload, arrhythmias, and aspiration from avid suckling. The patient should be monitored closely to avoid undertreatment or overtreatment. Undertreatment may have deleterious effects on intellectual development and linear growth. Overtreatment has been associated with craniosynostosis in infants, and may adversely affect the tempo of brain maturation and accelerate the bone age with resultant premature closure of the epiphyses and compromised adult stature. Acquired Hypothyroidism In Pediatric Patients The patient should be monitored closely to avoid undertreatment and overtreatment. Undertreatment may result in poor school performance due to impaired concentration and slowed mentation and in reduced adult height. Overtreatment may accelerate the bone age and result in premature epiphyseal closure and compromised adult stature. Treated children may manifest a period of catch-up growth, which may be adequate in some cases to normalize adult height. In children with severe or prolonged hypothyroidism, catch-up growth may not be adequate to normalize adult height. Geriatric Use Because of the increased prevalence of cardiovascular disease among the elderly, levothyroxine therapy should not be initiated at the full replacement dose (see WARNINGS , PRECAUTIONS, and DOSAGE AND ADMINISTRATION).

WARNINGS Included as part of the PRECAUTIONS section. PRECAUTIONS Risk Of Cardiac Complications In Elderly And In Patients With Cardiovascular Disease Excessive bolus dosing of Levothyroxine Sodium for Injection (greater than 500 mcg) are associated with cardiac complications, particularly in the elderly and in patients with an underlying cardiac condition. Adverse events that can potentially be related to the administration of large doses of Levothyroxine Sodium for Injection include arrhythmias, tachycardia, myocardial ischemia and infarction, or worsening of congestive heart failure and death. Cautious use, including doses in the lower end of the recommended range, may be warranted in these populations. Close observation of the patient following the administration of Levothyroxine Sodium for Injection is advised. Need For Concomitant Glucocorticoids And Monitoring For Other Diseases In Patients With Endocrine Disorders Occasionally, chronic autoimmune thyroiditis, which can lead to myxedema coma, may occur in association with other autoimmune disorders such as adrenal insufficiency, pernicious anemia, and insulin-dependent diabetes mellitus. Patients should be treated with replacement glucocorticoids prior to initiation of treatment with Levothyroxine Sodium for Injection, until adrenal function has been adequately assessed. Failure to do so may precipitate an acute adrenal crisis when thyroid hormone therapy is initiated, due to increased metabolic clearance of glucocorticoids by thyroid hormone. With initiation of Levothyroxine Sodium for Injection, patients with myxedema coma should also be monitored for previously undiagnosed diabetes insipidus. Not Indicated For Treatment Of Obesity Thyroid hormones, including Levothyroxine Sodium for Injection, either alone or with other therapeutic agents, should not be used for the treatment of obesity or for weight loss. In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines such as those used for their anorectic effects [see ADVERSE REACTIONS and OVERDOSAGE]. Nonclinical Toxicology Carcinogenesis, Mutagenesis, Impairment Of Fertility Animal studies have not been performed to evaluate the carcinogenic potential, mutagenic potential or effects on fertility of Levothyroxine Sodium for Injection. Use In Specific Populations Pregnancy Pregnancy Category A There are no reported cases of Levothyroxine Sodium for Injection used to treat myxedema coma in patients who were pregnant or lactating. Studies in pregnant women treated with oral levothyroxine to maintain a euthyroid state have not shown an increased risk of fetal abnormalities. Therefore, pregnant patients who develop myxedema should be treated with Levothyroxine Sodium for Injection as the risk of nontreatment is associated with a high probability of significant morbidity or mortality to the maternal patient and the fetus. Labor And Delivery Patients in labor who develop myxedema have not been reported in the literature. However, patients should be treated with Levothyroxine Sodium for Injection as the risk of non-treatment is associated with a high probability of significant morbidity or mortality to the maternal patient and the fetus. Nursing Mothers Adequate replacement doses of thyroid hormones are required to maintain normal lactation. There are no reported cases of Levothyroxine Sodium for Injection used to treat myxedema coma in patients who are lactating. However, such patients should be treated with Levothyroxine Sodium for Injection as the risk of nontreatment is associated with a high probability of significant morbidity or mortality to the nursing patient. Pediatric Use Myxedema coma is a disease of the elderly. An approved, oral dosage form of levothyroxine should be used in the pediatric patient population for maintaining a euthyroid state in non-complicated hypothyroidism. Geriatric Use And Patients With Underlying Cardiovascular Disease See Section 2, Dosage and Administration, for full prescribing information in the geriatric patient population. Because of the increased prevalence of cardiovascular disease in the elderly, cautious use of Levothyroxine Sodium for Injection in the elderly and in patients with known cardiac risk factors is advised. Atrial fibrillation is a common side effect associated with levothyroxine treatment in the elderly [see DOSAGE AND ADMINISTRATION and WARNINGS AND PRECAUTIONS].

WARNINGS WARNING : Thyroid hormones, including LEVOTHROID® (levothyroxine sodium) , either alone or with other therapeutic agents, should not be used for the treatment of obesity or for weight loss. In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduc-tion. Larger doses may produce serious or even life threatening manifestations of toxicity, particularly when given in association with sym-pathomimetic amines such as those used for their anorectic effects. Levothyroxine sodium should not be used in the treatment of male or female infertility unless this condition is associated with hypothyroidism. In patients with nontoxic diffuse goiter or nodular thyroid disease, particularly the elderly or those with underlying cardiovascular disease, levothyroxine sodium therapy is contraindicated if the serum TSH level is already suppressed due to the risk of precipitating overt thyrotoxicosis (see CONTRAINDICATIONS). If the serum TSH level is not suppressed, LEVOTHROID® (levothyroxine sodium) should be used with caution in conjunction with careful monitoring of thyroid function for evidence of hyperthyroidism and clinical monitoring for potential associated adverse cardiovascular signs and symptoms of hyperthyroidism. PRECAUTIONS General Levothyroxine has a narrow therapeutic index. Regardless of the indication for use, careful dosage titration is necessary to avoid the consequences of over-or under-treatment. These consequences include, among others, effects on growth and development, cardiovascular function, bone metabolism, reproductive function, cognitive function, emotional state, gastrointestinal function, and on glucose and lipid metabolism. Many drugs interact with levothyroxine sodium, necessitating adjustments in dosing to maintain therapeutic response (see DRUG INTERACTIONS). Effects on bone mineral density In women, long-term levothyroxine sodium therapy has been associated with increased bone resorption, thereby decreasing bone mineral density, especially in post-menopausal women on greater than replacement doses or in women who are receiving suppressive doses of levothyroxine sodium. The increased bone resorption may be associated with increased serum levels and urinary excretion of calcium and phosphorous, elevations in bone alkaline phosphatase and suppressed serum parathyroid hormone levels. Therefore, it is recommended that patients receiving levothyroxine sodium be given the minimum dose necessary to achieve the desired clinical and biochemical response. Patients with underlying cardiovascular disease Exercise caution when administering levothyroxine to patients with cardiovascular disorders and to the elderly in whom there is an increased risk of occult cardiac disease. In these patients, levothyroxine therapy should be initiated at lower doses than those recommended in younger individuals or in patients without cardiac disease (see WARNINGS; PRECAUTIONS, Geriatric Use;and DOSAGE AND ADMINISTRATION). If cardiac symptoms develop or worsen, the levothyroxine dose should be reduced or withheld for one week and then cautiously restarted at a lower dose. Overtreatment with levothyroxine sodium may have adverse cardiovascular effects such as an increase in heart rate, cardiac wall thickness, and cardiac contractility and may precipitate angina or arrhythmias. Patients with coronary artery disease who are receiving levothyrox-ine therapy should be monitored closely during surgical procedures, since the possibility of precipitating cardiac arrhythmias may be greater in those treated with levothyroxine. Concomitant administration of levothyroxine and sympathomimetic agents to patients with coronary artery disease may precipitate coronary insufficiency. Patients with nontoxic diffuse goiter or nodular thyroid disease Exercise caution when administering levothyroxine to patients with nontoxic diffuse goiter or nodular thyroid disease in order to prevent precipitation of thyrotoxicosis (see WARNINGS). If the serum TSH is already suppressed, levothyrox-ine sodium should not be administered (see CONTRAINDICATIONS). Associated endocrine disorders Hypothalamic/pituitary hormone deficiencies In patients with secondary or tertiary hypothyroidism, additional hypothalamic/pituitary hormone deficiencies should be considered, and, if diagnosed, treated (see PRECAUTIONS, Autoimmune polyglandular syndrome for adrenal insufficiency). Autoimmune polyglandular syndrome Occasionally, chronic autoimmune thyroiditis may occur in association with other autoimmune disorders such as adrenal insufficiency, pernicious anemia, and insulin-dependent diabetes mellitus. Patients with concomitant adrenal insufficiency should be treated with replacement glucocorticoids prior to initiation of treatment with levothyroxine sodium. Failure to do so may precipitate an acute adrenal crisis when thyroid hormone therapy is initiated, due to increased metabolic clearance of glucocorticoids by thyroid hormone. Patients with diabetes mellitus may require upward adjustments of their antidiabetic therapeutic regimens when treated with levothyroxine (see PRECAUTIONS, DRUG INTERACTIONS). Other associated medical conditions Infants with congenital hypothyroidism appear to be at increased risk for other congenital anomalies, with cardiovascular anomalies (pulmonary stenosis, atrial septal defect, and ventricular septal defect) being the most common association. Laboratory Tests General The diagnosis of hypothyroidism is confirmed by measuring TSH levels using a sensitive assay (second generation assay sensitivity ≤ 0. 1 mIU/L or third generation assay sensitivity ≤ 0. 01 mIU/L) and measurement of free-T4. The adequacy of therapy is determined by periodic assessment of appropriate laboratory tests and clinical evaluation. The choice of laboratory tests depends on various factors including the etiology of the underlying thyroid disease, the presence of concomitant medical conditions, including pregnancy, and the use of concomitant medications (see PRECAUTIONS, DRUG INTERACTIONS and Drug-Laboratory Test Interactions). Persistent clinical and laboratory evidence of hypothyroidism despite an apparent adequate replacement dose of LEVOTHROID® (levothyroxine sodium) may be evidence of inadequate absorption, poor compliance, drug interactions, or decreased T4 potency of the drug product. Adults In adult patients with primary (thyroidal) hypothyroidism, serum TSH levels (using a sensitive assay) alone may be used to monitor therapy. The frequency of TSH monitoring during levothyroxine dose titration depends on the clinical situation but it is generally recommended at 6-8 week intervals until nor-malization. For patients who have recently initiated levothyroxine therapy and whose serum TSH has normalized or in patients who have had their dosage of levothyroxine changed, the serum TSH concentration should be measured after 8-12 weeks. When the optimum replacement dose has been attained, clinical (physical examination) and biochemical monitoring may be performed every 6-12 months, depending on the clinical situation, and whenever there is a change in the patient's status. It is recommended that a physical examination and a serum TSH measurement be performed at least annually in patients receiving LEVOTHROID® (levothyroxine sodium) (see WARNINGS, PRECAUTIONS, and DOSAGE AND ADMINISTRATION). Pediatrics In patients with congenital hypothyroidism, the adequacy of replacement therapy should be assessed by measuring both serum TSH (using a sensitive assay) and total- or free-T4. During the first three years of life, the serum total- or free-T4 should be maintained at all times in the upper half of the normal range. While the aim of therapy is to also normalize the serum TSH level, this is not always possible in a small percentage of patients, particularly in the first few months of therapy. TSH may not normalize due to a resetting of the pituitary-thyroid feedback threshold as a result of in utero hypothy-roidism. Failure of the serum T4 to increase into the upper half of the normal range within 2 weeks of initiation of LEVOTHROID® (levothyroxine sodium) therapy and/or of the serum TSH to decrease below 20mU/L within 4 weeks should alert the physician to the possibility that the child is not receiving adequate therapy. Careful inquiry should then be made regarding compliance, dose of medication administered, and method of administration prior to raising the dose of LEVOTHROID® (levothyroxine sodium) . The recommended frequency of monitoring of TSH and total- or free-T4 in children is as follows: at 2 and 4 weeks after the initiation of treatment;every 1-2 months during the first year of life;every 2-3 months between 1 and 3 years of age;and every 3 to 12 months thereafter until growth is completed. More frequent intervals of monitoring may be necessary if poor compliance is suspected or abnormal values are obtained. It is recommended that TSH and T4 levels, and a physical examination, if indicated, be performed 2 weeks after any change in LEVOTHROID® (levothyroxine sodium) dosage. Routine clinical examination, including assessment of mental and physical growth and development, and bone maturation, should be performed at regular intervals (see PRECAUTIONS, Pediatric Use and DOSAGE AND ADMINISTRATION). Secondary (pituitary) and tertiary (hypothalamic) hypothyroidism Adequacy of therapy should be assessed by measuring serum free-T4 levels, which should be maintained in the upper half of the normal range in these patients. Carcinogenesis, Mutagenesis, and Impairment of Fertility Animal studies have not been performed to evaluate the carcinogenic potential, mutagenic potential or effects on fertility of levothyroxine. The synthetic T4 in LEVOTHROID® (levothyroxine sodium) is identical to that produced naturally by the human thyroid gland. Although there has been a reported association between prolonged thyroid hormone therapy and breast cancer, this has not been confirmed. Patients receiving LEVOTHROID® (levothyroxine sodium) for appropriate clinical indications should be titrated to the lowest effective replacement dose. Pregnancy Category A Studies in women taking levothyroxine sodium during pregnancy have not shown an increased risk of congenital abnormal-ities. Therefore, the possibility of fetal harm appears remote. LEVOTHROID® (levothyroxine sodium) should not be discontinued during pregnancy and hypothyroidism diagnosed during pregnancy should be promptly treated. Hypothyroidism during pregnancy is associated with a higher rate of complications, including spontaneous abortion, pre-eclampsia, stillbirth and premature delivery. Maternal hypothyroidism may have an adverse effect on fetal and childhood growth and development. During pregnancy, serum T4 levels may decrease and serum TSH levels increase to values outside the normal range. Since elevations in serum TSH may occur as early as 4 weeks gestation, pregnant women taking LEVOTHROID® (levothyroxine sodium) should have their TSH measured during each trimester. An elevated serum TSH level should be corrected by an increase in the dose of LEVOTHROID® (levothyroxine sodium) . Since postpartum TSH levels are similar to preconception values, the LEVOTHROID® (levothyroxine sodium) dosage should return to the pre-pregnancy dose immediately after delivery. A serum TSH level should be obtained 6-8 weeks postpartum. Thyroid hormones cross the placental barrier to some extent as evidenced by levels in cord blood of athyreotic fetuses being approximately one-third maternal levels. Transfer of thyroid hormone from the mother to the fetus, however, may not be adequate to prevent in utero hypothyroidism. Nursing Mothers Although thyroid hormones are excreted only minimally in human milk, caution should be exercised when LEVOTHROID® (levothyroxine sodium) is administered to a nursing woman. However, adequate replacement doses of levothyroxine are generally needed to maintain normal lactation. Pediatric Use General The goal of treatment in pediatric patients with hypothyroidism is to achieve and maintain normal intellectual and physical growth and development. The initial dose of levothyroxine varies with age and body weight (see DOSAGE AND ADMINISTRATION, Table 3). Dosing adjustments are based on an assessment of the individual patient's clinical and laboratory parameters (see PRECAUTIONS, Laboratory Tests). In children in whom a diagnosis of permanent hypothyroidism has not been established, it is recommended that levothyroxine administration be discontinued for a 30-day trial period, but only after the child is at least 3 years of age. Serum T4 and TSH levels should then be obtained. If the T4 is low and the TSH high, the diagnosis of permanent hypothyroidism is established, and levothyroxine therapy should be reinstituted. If the T4 and TSH levels are normal, euthyroidism may be assumed and, therefore, the hypothyroidism can be considered to have been transient. In this instance, however, the physician should carefully monitor the child and repeat the thyroid function tests if any signs or symptoms of hypothyroidism develop. In this setting, the clinician should have a high index of suspicion of relapse. If the results of the levothyroxine withdrawal test are inconclusive, careful follow-up and subsequent testing will be necessary. Since some more severely affected children may become clinically hypothyroid when treatment is discontinued for 30 days, an alternate approach is to reduce the replacement dose of levothyroxine by half during the 30-day trial period. If, after 30 days, the serum TSH is elevated above 20 mU/L, the diagnosis of permanent hypothyroidism is confirmed, and full replacement therapy should be resumed. However, if the serum TSH has not risen to greater than 20 mU/L, levothyroxine treatment should be discontinued for another 30-day trial period followed by repeat serum T4 and TSH testing. The presence of concomitant medical conditions should be considered in certain clinical circumstances and, if present, appropriately treated (see PRECAUTIONS). Congenital Hypothyroidism (see PRECAUTIONS, Laboratory Tests and DOSAGE AND ADMINISTRATION) Rapid restoration of normal serum T4 concentrations is essential for preventing the adverse effects of congenital hypothyroidism on intellectual development as well as on overall physical growth and maturation. Therefore, LEVOTHROID® (levothyroxine sodium) therapy should be initiated immediately upon diagnosis and is generally continued for life. During the first 2 weeks of LEVOTHROID® (levothyroxine sodium) therapy, infants should be closely monitored for cardiac overload, arrhythmias, and aspiration from avid suckling. The patient should be monitored closely to avoid undertreatment or overtreatment. Undertreatment may have deleterious effects on intellectual development and linear growth. Overtreatment has been associated with craniosynostosis in infants, and may adversely affect the tempo of brain maturation and accelerate the bone age with resultant premature closure of the epiphyses and compromised adult stature. Acquired Hypothyroidism in Pediatric Patients The patient should be monitored closely to avoid undertreatment and overtreatment. Undertreatment may result in poor school performance due to impaired concentration and slowed mentation and in reduced adult height. Overtreatment may accelerate the bone age and result in premature epiphy-seal closure and compromised adult stature. Treated children may manifest a period of catch-up growth, which may be adequate in some cases to normalize adult height. In children with severe or prolonged hypothyroidism, catch-up growth may not be adequate to normalize adult height. Geriatric Use Because of the increased prevalence of cardiovascular disease among the elderly, levothyroxine therapy should not be initiated at the full replacement dose (see WARNINGS, PRECAUTIONS, and DOSAGE AND ADMINISTRATION).