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CLINICAL PHARMACOLOGY Mechanism of Action All of digoxin's actions are mediated through its effects on Na-K ATPase. This enzyme, the “sodium pump,” is responsible for maintaining the intracellular milieu throughout the body by moving sodium ions out of and potassium ions into cells. By inhibiting Na-K ATPase, digoxin causes increased availability of intracellular calcium in the myocardium and conduction system, with consequent increased inotropy, increased automaticity, and reduced conduction velocity indirectly causes parasympathetic stimulation of the autonomic nervous system, with consequent effects on the sino-atrial (SA) and atrioventricular (AV) nodes reduces catecholamine reuptake at nerve terminals, rendering blood vessels more sensitive to endogenous or exogenous catecholamines increases baroreceptor sensitization, with consequent increased carotid sinus nerve activity and enhanced sympathetic withdrawal for any given increment in mean arterial pressure increases (at higher concentrations) sympathetic outflow from the central nervous system (CNS) to both cardiac and peripheral sympathetic nerves allows (at higher concentrations) progressive efflux of intracellular potassium, with consequent increase in serum potassium levels. The cardiologic consequences of these direct and indirect effects are an increase in the force and velocity of myocardial systolic contraction (positive inotropic action), a slowing of the heart rate (negative chronotropic effect), decreased conduction velocity through the AV node, and a decrease in the degree of activation of the sympathetic nervous system and renin-angiotensin system (neurohormonal deactivating effect). Pharmacodynamics The times to onset of pharmacologic effect and to peak effect of preparations of LANOXIN are shown in Table 7. Table 7: Times to Onset of Pharmacologic Effect and to Peak Effect of Preparations of LANOXIN Product Time to Onset of Effecta Time to Peak Effecta LANOXIN Tablets 0.5 -2 hours 2 -6 hours LANOXIN Injection/IV 5 -30 minutes b 1 -4 hours aDocumented for ventricular response rate in atrial fibrillation, inotropic effects and electrocardiographic changes. bDepending upon rate of infusion. Hemodynamic Effects Short-and long-term therapy with the drug increase cardiac output and lowers pulmonary artery pressure, pulmonary capillary wedge pressure, and systemic vascular resistance in patients with heart failure. These hemodynamic effects are accompanied by an increase in the left ventricular ejection fraction and a decrease in end-systolic and end-diastolic dimensions. ECG Changes The use of therapeutic doses of LANOXIN may cause prolongation of the PR interval and depression of the ST segment on the electrocardiogram. LANOXIN may produce false positive ST-T changes on the electrocardiogram during exercise testing. These electrophysiologic effects are not indicative of toxicity. LANOXIN does not significantly reduce heart rate during exercise. Pharmacokinetics Absorption Following oral administration, peak serum concentrations of digoxin occur at 1 to 3 hours. Absorption of digoxin from LANOXIN Tablets has been demonstrated to be 60% to 80% complete compared to an identical intravenous dose of digoxin (absolute bioavailability). When LANOXIN Tablets are taken after meals, the rate of absorption is slowed, but the total amount of digoxin absorbed is usually unchanged. When taken with meals high in bran fiber, however, the amount absorbed from an oral dose may be reduced. Comparisons of the systemic availability and equivalent doses for oral preparations of LANOXIN are shown in Dosage and Administration (2.6). Digoxin is a substrate for P-glycoprotein. As an efflux protein on the apical membrane of enterocytes, P-glycoprotein may limit the absorption of digoxin. In some patients, orally administered digoxin is converted to inactive reduction products (e.g., dihydrodigoxin) by colonic bacteria in the gut. Data suggest that 1 in 10 patients treated with digoxin tablets, colonic bacteria will degrade 40% or more of the ingested dose. As a result, certain antibiotics may increase the absorption of digoxin in such patients. Although inactivation of these bacteria by antibiotics is rapid, the serum digoxin concentration will rise at a rate consistent with the elimination half-life of digoxin. Serum digoxin concentration relates to the extent of bacterial inactivation, and may be as much as doubled in some cases [see DRUG INTERACTIONS]. Patients with malabsorption syndromes (e.g., short bowel syndrome, celiac sprue, jejunoileal bypass) may have a reduced ability to absorb orally administered digoxin. Distribution Following drug administration, a 6-to 8-hour tissue distribution phase is observed. This is followed by a much more gradual decline in the serum concentration of the drug, which is dependent on the elimination of digoxin from the body. The peak height and slope of the early portion (absorption/distribution phases) of the serum concentration-time curve are dependent upon the route of administration and the absorption characteristics of the formulation. Clinical evidence indicates that the early high serum concentrations do not reflect the concentration of digoxin at its site of action, but that with chronic use, the steady-state post-distribution serum concentrations are in equilibrium with tissue concentrations and correlate with pharmacologic effects. In individual patients, these post-distribution serum concentrations may be useful in evaluating therapeutic and toxic effects [see DOSAGE AND ADMINISTRATION]. Digoxin is concentrated in tissues and therefore has a large apparent volume of distribution (approximately 475 to 500L). Digoxin crosses both the blood-brain barrier and the placenta. At delivery, the serum digoxin concentration in the newborn is similar to the serum concentration in the mother. Approximately 25% of digoxin in the plasma is bound to protein. Serum digoxin concentrations are not significantly altered by large changes in fat tissue weight, so that its distribution space correlates best with lean (i.e., ideal) body weight, not total body weight. Metabolism Only a small percentage (13%) of a dose of digoxin is metabolized in healthy volunteers. The urinary metabolites, which include dihydrodigoxin, digoxigenin bisdigitoxoside, and their glucuronide and sulfate conjugates, are polar in nature and are postulated to be formed via hydrolysis, oxidation, and conjugation. The metabolism of digoxin is not dependent upon the cytochrome P-450 system, and digoxin is not known to induce or inhibit the cytochrome P-450 system. Excretion Elimination of digoxin follows first-order kinetics (that is, the quantity of digoxin eliminated at any time is proportional to the total body content). Following intravenous administration to healthy volunteers, 50% to 70% of a digoxin dose is excreted unchanged in the urine. Renal excretion of digoxin is proportional to creatinine clearance and is largely independent of urine flow. In healthy volunteers with normal renal function, digoxin has a half-life of 1.5 to 2 days. The half-life in anuric patients is prolonged to 3.5 to 5 days. Digoxin is not effectively removed from the body by dialysis, exchange transfusion, or during cardiopulmonary bypass because most of the drug is bound to extravascular tissues. Special Populations Geriatrics: Because of age-related declines in renal function, elderly patients would be expected to eliminate digoxin more slowly than younger subjects. Elderly patients may also exhibit a lower volume of distribution of digoxin due to age-related loss of lean muscle mass. Thus, the dosage of digoxin should be carefully selected and monitored in elderly patients [see Use In Specific Populations]. Gender: In a study of 184 patients, the clearance of digoxin was 12% lower in females than in male patients. This difference is not likely to be clinically important. Hepatic Impairment: Because only a small percentage (approximately 13%) of a dose of digoxin undergoes metabolism, hepatic impairment would not be expected to significantly alter the pharmacokinetics of digoxin. In a small study, plasma digoxin concentration profiles in patients with acute hepatitis generally fell within the range of profiles in a group of healthy subjects. No dosage adjustments are recommended for patients with hepatic impairment; however, serum digoxin concentrations should be used as appropriate to help guide dosing in these patients. Renal Impairment: Since the clearance of digoxin correlates with creatinine clearance, patients with renal impairment generally demonstrate prolonged digoxin elimination half-lives and greater exposures to digoxin. Therefore, digoxin must be carefully titrated in these patients based on clinical response, and based on monitoring of serum digoxin concentrations, as appropriate. Race: The impact of race differences on digoxin pharmacokinetics has not been formally studied. Because digoxin is primarily eliminated as unchanged drug via the kidney and because there are no important differences in creatinine clearance among races, pharmacokinetic differences due to race are not expected. Drug-drug Interactions Based on literature reports no significant changes in digoxin exposure were reported when digoxin was co-administered with the following drugs: alfuzosin, aliskiren, amlodipine, aprepitant, argatroban, aspirin, atorvastatin, benazepril, bisoprolol, black cohosh, bosentan, candesartan, citalopram, clopidogrel, colesevelam, dipyridamole, disopyramide, donepezil, doxazosin, dutasteride, echinacea, enalapril, eprosartan, ertapenem, escitalopram, esmolol, ezetimibe, famciclovir, felodipine, finasteride, flecainide, fluvastatin, fondaparinux, galantamine, gemifloxacin, grapefruit juice, irbesartan, isradipine, ketorlac, levetiracetam, levofloxacin, lisinopril, losartan, lovastatin, meloxicam, mexilitine, midazolam, milk thistle, moexipril, montelukast, moxifloxacin, mycophenolate, nateglinide, nesiritide, nicardipine, nisoldipine, olmesartan, orlistat, pantoprazole, paroxetine,perindopril, pioglitazone, pravastatin, prazosin, procainamide, quinapril, raloxifene, ramipril, repaglinide, rivastigmine, rofecoxib, ropinirole, rosiglitazone, rosuvastatin, sertraline, sevelamer, simvastatin, sirolimus, solifenacin, tamsulosin, tegaserod, terbinafine, tiagabine, ticlopidine, tigecycline, topiramate, torsemide, tramadol, trandolapril, triamterene, trospium, trovafloxacin, valacyclovir, valsartan, varenicline, voriconazole, zaleplon, zolpidem Clinical Studies Chronic Heart Failure Two 12-week, double-blind, placebo-controlled studies enrolled 178 (RADIANCE trial) and 88 (PROVED trial) patients with NYHA class II or III heart failure previously treated with digoxin, a diuretic, and an ACE inhibitor (RADIANCE only) and randomized them to placebo or treatment with LANOXIN. Both trials demonstrated better preservation of exercise capacity in patients randomized to LANOXIN. Continued treatment with LANOXIN reduced the risk of developing worsening heart failure, as evidenced by heart failure-related hospitalizations and emergency care and the need for concomitant heart failure therapy. Dig Trial of LANOXIN in Patients with Heart Failure The Digitalis Investigation Group (DIG) main trial was a 37-week, multicenter, randomized, double-blind mortality study comparing digoxin to placebo in 6800 adult patients with heart failure and left ventricular ejection fraction ≤ 0.45. At randomization, 67% were NYHA class I or II, 71% had heart failure of ischemic etiology, 44% had been receiving digoxin, and most were receiving a concomitant ACE inhibitor (94%) and diuretics (82%). As in the smaller trials described above, patients who had been receiving open-label digoxin were withdrawn from this treatment before randomization. Randomization to digoxin was again associated with a significant reduction in the incidence of hospitalization, whether scored as number of hospitalizations for heart failure (relative risk 75%), risk of having at least one such hospitalization during the trial (RR 72%), or number of hospitalizations for any cause (RR 94%). On the other hand, randomization to digoxin had no apparent effect on mortality (RR 99%, with confidence limits of 91 to 107%). Chronic Atrial Fibrillation Digoxin has also been studied as a means of controlling the ventricular response to chronic atrial fibrillation in adults. Digoxin reduced the resting heart rate, but not the heart rate during exercise. In 3 different randomized, double-blind trials that included a total of 315 adult patients, digoxin was compared to placebo for the conversion of recent-onset atrial fibrillation to sinus rhythm. Conversion was equally likely, and equally rapid, in the digoxin and placebo groups. In a randomized 120-patient trial comparing digoxin, sotalol, and amiodarone, patients randomized to digoxin had the lowest incidence of conversion to sinus rhythm, and the least satisfactory rate control when conversion did not occur. In at least one study, digoxin was studied as a means of delaying reversion to atrial fibrillation in adult patients with frequent recurrence of this arrhythmia. This was a randomized, double-blind, 43-patient crossover study. Digoxin increased the mean time between symptomatic recurrent episodes by 54%, but had no effect on the frequency of fibrillatory episodes seen during continuous electrocardiographic monitoring.

CLINICAL PHARMACOLOGY Mechanism of Action Digoxin inhibits sodium-potassium ATPase, an enzyme that regulates the quantity of sodium and potassium inside cells. Inhibition of the enzyme leads to an increase in the intracellular concentration of sodium and thus (by stimulation of sodium-calcium exchange) an increase in the intracellular concentration of calcium. The beneficial effects of digoxin result from direct actions on cardiac muscle, as well as indirect actions on the cardiovascular system mediated by effects on the autonomic nervous system. The autonomic effects include: (1) a vagomimetic action, which is responsible for the effects of digoxin on the sinoatrial and atrioventricular (AV) nodes; and (2) baroreceptor sensitization, which results in increased afferent inhibitory activity and reduced activity of the sympathetic nervous system and renin-angiotensin system for any given increment in mean ar terial pressure. The pharmacologic consequences of these direct and indirect effects are: (1) an increase in the force and velocity of myocardial systolic contraction (positive inotropic action); (2) a decrease in the degree of activation of the sympathetic nervous system and renin-angiotensin system (neurohormonal deactivating effect); and (3) slowing of the heart rate and decreased conduction velocity through the AV node (vagomimetic effect). The effects of digoxin in heart failure are mediated by its positive inotropic and neurohormonal deactivating effects, whereas the effects of the drug in atrial arrhythmias are related to its vagomimetic actions. In high doses, digoxin increases sympathetic outflow from the central nervous system (CNS). This increase in sympathetic activit y may be an important factor in digitalis toxicity. Pharmacokinetics: Absorption: Following oral administration, peak serum concentrations of digoxin occur at 1 to 3 hours. Absorption of digoxin from digoxin tablets has been demonstrated to be 60% to 80% complete compared to an identical intravenous dose of digoxin (absolute bioavailability) or Digoxin Solution in Capsules (relative bioavailability). When digoxin tablets are taken after meals, the rate of absorption is slowed, but the total amount of digoxin absorbed is usually unchanged. When taken with meals high in bran fiber, however, the amount absorbed from an oral dose may be reduced. Comparisons of the systemic availability and equivalent doses for oral preparations of digoxin are shown in Table 1: Table 1: Comparisons of the Systemic Availability and Equivalent Doses for Oral Preparations of Digoxin Product Absolute Bio- availability Equivalent Doses(mcg)* Among Dosage Forms Digoxin Tablets 60-80% 62.5 125 250 500 Digoxin Pediatric Elixir 70-85% 62.5 125 250 500 Digoxin Solution in Capsules 90-100% 50 100 200 400 Digoxin Injection/IV 100% 50 100 200 400 *For example, 125-mcg Digoxin Tablets equivalent to 125 mcg Digoxin Pediatric Elixir equivalent to 100 mcg Digoxin Solution in Capsules equivalent to 100 mcg Digoxin Injection/IV. In some patients, orally administered digoxin is conver ted to inactive reduction products (e.g., dihydrodigoxin) by colonic bacteria in the gut. Data suggest that one in ten patients treated with digoxin tablets will degrade 40% or more of the ingested dose. As a result, certain antibiotics may increase the absorption of digoxin in such patients. Although inactivation of these bacteria by antibiotics is rapid, the serum digoxin concentration will rise at a rate consistent with the elimination half-life of digoxin. The magnitude of rise in serum digoxin concentration relates to the extent of bacterial inactivation, and may be as much as two-fold in some cases. Distribution: Following drug administration, a 6-to 8-hour tissue distribution phase is observed. This is followed by a much more gradual decline in the serum concentration of the drug, which is dependent on the elimination of digoxin from the body. The peak height and slope of the early portion (absorption/distribution phases) of the serum concentration-time curve are dependent upon the route of administration and the absorption characteristics of the formulation. Clinical evidence indicates that the early high serum concentrations do not reflect the concentration of digoxin at its site of action, but that with chronic use, the steady-state post-distribution serum concentrations are in equilibrium with tissue concentrations and correlate with pharmacologic effects. In individual patients, these post-distribution serum concentrations may be useful in evaluating therapeutic and toxic effects (see DOSAGE AND ADMINISTRATION: Serum Digoxin Concentrations). Digoxin is concentrated in tissues and therefore has a large apparent volume of distribution. Digoxin crosses both the blood-brain barrier and the placenta. At delivery, the serum digoxin concentration in the newborn is similar to the serum concentration in the mother. Approximately 25% of digoxin in the plasma is bound to protein. Serum digoxin concentrations are not significantly altered by large changes in fat tissue weight, so that its distribution space correlates best with lean (i.e., ideal) body weight, not total body weight. Metabolism: Only a small percentage (16%) of a dose of digoxin is metabolized. The end metabolites, which include 3 β-digoxigenin, 3-keto-digoxigenin, and their glucuronide and sulfate conjugates, are polar in nature and are postulated to be formed via hydrolysis, oxidation, and conjugation. The metabolism of digoxin is not dependent upon the cytochrome P-450 system, and digoxin is not known to induce or inhibit the cytochrome P-450 system. Excretion: Elimination of digoxin follows first-order kinetics (that is, the quantity of digoxin eliminated at any time is propor tional to the total body content). Following intravenous administration to healthy volunteers, 50% to 70% of a digoxin dose is excreted unchanged in the urine. Renal excretion of digoxin is proportional to glomerular filtration rate and is largely independent of urine flow. In healthy volunteers with normal renal function, digoxin has a half-life of 1.5 to 2 days. The half-life in anuric patients is prolonged to 3.5 to 5 days. Digoxin is not effectively removed from the body by dialysis, exchange transfusion, or during cardiopulmonar y bypass because most of the drug is bound to tissue and does not circulate in the blood. Special Populations: Race differences in digoxin pharmacokinetics have not been formally studied. Because digoxin is primarily eliminated as unchanged drug via the kidney and because there are no important differences in creatinine clearance among races, pharmacokinetic differences due to race are not expected. The clearance of digoxin can be primarily correlated with renal function as indicated by creatinine clearance. The Cockcroft and Gault formula for estimation of creatinine clearance includes age, body weight, and gender. A table that provides the usual daily maintenance dose requirements of digoxin tablets based on creatinine clearance (per 70 kg) is presented in the DOSAGE AND ADMINISTRATION section. Plasma digoxin concentration profiles in patients with acute hepatitis generally fell within the range of profiles in a group of healthy subjects. Pharmacodynamic and Clinical Effects: The times to onset of pharmacologic effect and to peak effect of preparations of digoxin are shown in Table 2: Table 2: Times to Onset of Pharmacologic Effect and to Peak Effect of Preparations of Digoxin Product Time to Onset of Effect* Time to Peak Effect* Digoxin Tablets 0.5-2 hours 2-6 hours Digoxin Pediatric Elixir 0.5-2 hours 2-6 hours Digoxin Solution in Capsules 0.5-2 hours 2-6 hours Digoxin Injection/IV 5-30 minutes† 1-4 hours *Documented for ventricular response rate in atrial fibrillation, inotropic effects and electrocardiographic changes. †Depending upon rate of infusion. Hemodynamic effects: Digoxin produces hemodynamic improvement in patients with heart failure. Short- and long-term therapy with the drug increases cardiac output and lowers pulmonary artery pressure, pulmonary capillary wedge pressure, and systemic vascular resistance. These hemodynamic effects are accompanied by an increase in the left ventricular ejection fraction and a decrease in end-systolic and end-diastolic dimensions. Chronic Heart Failure: Two 12-week, double-blind, placebo-controlled studies enrolled 178 (RADIANCE trial) and 88 (PROVED trial) patients with NYHA class II or III heart failure previously treated with digoxin, a diuretic, and an ACE inhibitor (RADIANCE only) and randomized them to placebo or treatment with digoxin. Both trials demonstrated better preservation of exercise capacit y in patients randomized to digoxin. Continued treatment with digoxin reduced the risk of developing worsening heart failure, as evidenced by heart failure-related hospitalizations and emergency care and the need for concomitant heart failure therapy. The larger study also showed treatment-related benefits in NYHA class and patients' global assessment. In the smaller trial, these trended in favor of a treatment benefit. The Digitalis Investigation Group (DIG) main trial was a multicenter, randomized, double-blind, placebo-controlled mortalit y study of 6,801 patients with heart failure and left ventricular ejection fraction ≤ 0.45. At randomization, 67% were NYHA class I or II, 71% had heart failure of ischemic etiology, 44% had been receiving digoxin, and most were receiving concomitant ACE inhibitor (94%) and diuretic (82%). Patients were randomized to placebo or digoxin, the dose of which was adjusted for the patient's age, sex, lean body weight, and serum creatinine (see DOSAGE AND ADMINISTRATION), and followed for up to 58 months (median 37 months). The median daily dose prescribed was 0.25 mg. Overall all-cause mortality was 35% with no difference between groups (95% confidence limits for relative risk of 0.91 to 1.07). Digoxin was associated with a 25% reduction in the number of hospitalizations for heart failure, a 28% reduction in the risk of a patient having at least one hospitalization for heart failure, and a 6.5% reduction in total hospitalizations (for any cause). Use of digoxin was associated with a trend in reduction in time to all-cause death or hospitalization. The trend was evident in subgroups of patients with mild heart failure as well as more severe disease, as shown in Table 3. Although the effect on all-cause death or hospitalization was not statistically significant, much of the apparent benefit derived from effects on mor tality and hospitalization attributed to heart failure. Table 3: Subgroup Analyses of Mortality and Hospitalization During the First Two Years Following Randomization. n Risk of All Cause Mortality or All Cause Hospitalization* Placebo Digoxin Relative risk All Patients (EF ≤ 0.45) 6801 604 593 0.94 (0.88-1.00) NYHA I/II 4571 549 541 0.96 (0.89-1.04) EF 0.25-0.45 4543 568 571 0.99 (0.91-1.07) CTR ≤ 0.55 4455 561 563 0.98 (0.91-1.06) NYHA III/IV 2224 719 696 0.88 (0.80-0.97) EF < 0.25 2258 677 637 0.84 (0.76-0.93) CTR > 0.55 2346 687 650 0.85 (0.77-0.94) EF > 0.45 987 571 585 1.04 (0.88-1.23) n Risk of HF Related Mortality or HF Related Hospitalization* Placebo Digoxin Relative risk All Patients (EF ≤ 0.45) 6801 294 217 0.69 (0.63-0.76) NYHA I/II 4571 242 178 0.70 (0.62-0.80) EF 0.25-0.45 4543 244 190 0.74 (0.66-0.84) CTR ≤ 0.55 4455 239 180 0.71 (0.63-0.81) NYHA III/IV 2224 402 295 0.65 (0.57-0.75) EF < 0.25 2258 394 270 0.61 (0.53-0.71) CTR > 0.55 2346 398 287 0.65 (0.57-0.75) EF > 0.45‡ 987 179 136 0.72 (0.53-0.99) *Number of patients with an event during the first 2 years per 1000 randomized patients. †Relative risk (95% confidence inter val). ‡DIG Ancillary Study. In situations where there is no statistically significant benefit of treatment evident from a trial's primary endpoint, results pertaining to a secondar y end-point should be interpreted cautiously. Chronic Atria Fibrillation: In patients with chronic atrial fibrillation, digoxin slows rapid ventricular response rate in linear dose-response fashion from 0.25 to 0.75 mg/day. Digoxin should not be used for the treatment of multifocal atrial tachycardia.

Find Lowest Prices on LANOXIN ®  (digoxin) DESCRIPTION LANOXIN (digoxin) is a cardiac glycoside, a closely related group of drugs having in common specific effects on the myocardium. These drugs are found in a number of plants. Digoxin is extracted from the leaves of Digitalis lanata. The term “digitalis” is used to designate the whole group of glycosides. The glycosides are composed of 2 portions: a sugar and a cardenolide (hence “glycosides”). Digoxin is described chemically as (3β,5β,12β)-3-[(O-2,6-dideoxy-β-D-ribo-hexopyranosyl(1→4)-O-2,6-dideoxy-β-D-ribo-hexopyranosyl-(1→4)-2,6-dideoxy-β-D-ribohexopyranosyl)oxy]-12,14-dihydroxy-card-20(22)-enolide. Its molecular formula is C41H64O14, its molecular weight is 780.95, and its structural formula is: Digoxin exists as odorless white crystals that melt with decomposition above 230°C. The drug is practically insoluble in water and in ether; slightly soluble in diluted (50%) alcohol and in chloroform; and freely soluble in pyridine. LANOXIN is supplied as 125 mcg (0.125-mg) or 250 mcg (0.25-mg) tablets for oral administration. Each tablet contains the labeled amount of digoxin USP and the following inactive ingredients: corn and potato starches, lactose, and magnesium stearate. In addition, the dyes used in the 125 mcg (0.125 mg) tablets are D&C Yellow No. 10 and FD&C Yellow No. 6.

Find Lowest Prices on DIGITEK® (digoxin) Tablets, USP DESCRIPTION DIGITEK (digoxin) is one of the cardiac (or digitalis) glycosides, a closely related group of drugs having in common specific effects on the myocardium. These drugs are found in a number of plants. Digoxin is extracted from the leaves of Digitalis lanata. The term "digitalis" is used to designate the whole group of glycosides. The glycosides are composed of two portions: a sugar and a cardenolide (hence "glycosides"). Digoxin is described chemically as (3 β, 5 β, 12 β)-3-[(O-2, 6-dideoxy-β-D-ribo-hexopyranosyl-(1→4)-O-2,6-dideoxy-β-D-ribo-hexopyranosyl- (1→4)-2,6-dideoxy-β-D-ribo-hexopyranosyl)oxy]-12,14-dihydroxy-card-20(22)-enolide. Its molecular formula is C41H64O14, its molecular weight is 780.94, and the structural formula shown: Digoxin exists as odorless white crystals that melt with decomposition above 230°C. The drug is practically insoluble in water and in ether; slightly soluble in diluted (50%) alcohol and in chloroform; and freely soluble in pyridine. DIGITEK (digoxin tablets) is supplied as 125-mcg (0.125-mg) or 250-mcg (0.25-mg) tablets for oral administration. Each tablet contains the labeled amount of digoxin USP and the following inactive ingredients: corn starch, croscarmellose sodium, microcrystalline cellulose, pregelatinized starch, lactose monohydrate and anhydrous lactose, silicon dioxide and stearic acid. In addition, the 125-mcg (0.125-mg) tablet contains D&C Yellow No. 10 Aluminum Lake.

INDICATIONS Heart Failure in Adults LANOXIN is indicated for the treatment of mild to moderate heart failure in adults. LANOXIN increases left ventricular ejection fraction and improves heart failure symptoms as evidenced by improved exercise capacity and decreased heart failure-related hospitalizations and emergency care, while having no effect on mortality. Where possible, LANOXIN should be used in combination with a diuretic and an angiotensin-converting enzyme (ACE) inhibitor. Heart Failure in Pediatric Patients LANOXIN increases myocardial contractility in pediatric patients with heart failure. Atrial Fibrillation in Adults LANOXIN is indicated for the control of ventricular response rate in adult patients with chronic atrial fibrillation. DOSAGE AND ADMINISTRATION Important Dosing Information In selecting a LANOXIN dosing regimen, it is important to consider factors that affect digoxin blood levels (e.g., body weight, age, renal function, concomitant drugs) since toxic levels of digoxin are only slightly higher than therapeutic levels. Dosing can be either initiated with a loading dose followed by maintenance dosing if rapid titration is desired or initiated with maintenance dosing without a loading dose. Consider interruption or reduction in digoxin dose prior to electrical cardioversion [see WARNINGS AND PRECAUTIONS]. Use digoxin solution to obtain the appropriate dose in infants, young pediatric patients, or patients with very low body weight. Loading Dosing Regimen in Adults and Pediatric Patients For adults and pediatric patients if a loading dosage is to be given, administer half the total loading dose initially, then ¼ the loading dose every 4 to 8 hours twice, with careful assessment of clinical response and toxicity before each dose. The recommended loading dose is displayed in Table 1. Table 1: Recommended LANOXIN Oral Loading Dose Age Oral Loading Dose, mcg/kg 5 to 10 years 20 -45 Adults and pediatric patients over 10 years 10-15 mcg = micrograms Maintenance Dosing in Adults and Pediatric Patients Over 10 Years Old The maintenance dose is based on the lean body weight, renal function, age, and concomitant products [see DRUG INTERACTIONS]. The recommended starting maintenance dosage in adults and pediatric patients over 10 years old is displayed in Table 2. Doses may be increased every 2 weeks according to clinical response, serum drug levels, and toxicity. Table 2: Recommended Starting LANOXIN Maintenance Dosage in Adults and Pediatric Patients Over 10 Years Old Age Oral Maintenance Dose, mcg/kg/day (given once daily) Adults and pediatric patients over 10 years 3.4 – 5.1 mcg = micrograms Table 3 displays the recommended (once daily) maintenance dose of LANOXIN in pediatric patients over 10 years old and adult patients according to lean body weight and renal function. The doses are based on studies in adult patients with heart failure. Alternatively, the maintenance dose may be estimated by the following formula (peak body stores lost each day through elimination): Total Maintenance Dose = Loading Dose (i.e., Peak Body Stores) x % Daily Loss/100 (% Daily Loss = 14 + Creatinine clearance/5) Reduce the dose of LANOXIN in patients whose lean weight is an abnormally small fraction of their total body mass because of obesity or edema. Table 3: Recommended Maintenance Dose (in micrograms given once daily) of LANOXIN in Pediatric Patients Over 10 Years Old and Adults by Lean Body Weight and by Renal Functiona Corrected Creatinine Clearanceb Lean Body Weightd Number of Days Before Steady State Achievedc kg 40 50 60 70 80 90 100 lb 88 110 132 154 176 198 220 10 mL/min 62.5* 125 125 187.5 187.5 187.5 250 19 20 mL/min 125 125 125 187.5 187.5 250 250 16 30 mL/min 125 125 187.5 187.5 250 250 312.5 14 40 mL/min 125 187.5 187.5 250 250 312.5 312.5 13 50 mL/min 125 187.5 187.5 250 250 312.5 312.5 12 60 mL/min 125 187.5 250 250 312.5 312.5 375 11 70 mL/min 187.5 187.5 250 250 312.5 375 375 10 80 mL/min 187.5 187.5 250 312.5 312.5 375 437.5 9 90 mL/min 187.5 250 250 312.5 375 437.5 437.5 8 100 mL/min 187.5 250 312.5 312.5 375 437.5 500 7 aDoses are rounded to the nearest dose possible using whole and/or half LANOXIN tablets. Recommended doses approximately 30 percent lower than the calculated dose are designated with an *. Monitor digoxin levels in patients receiving these initial doses and increase dose if needed. . bFor adults, creatinine clearance was corrected to 70-kg body weight or 1.73 m² body surface area. If only serum creatinine concentrations (Scr) are available, a corrected Ccr may be estimated in men as (140 – Age)/Scr. For women, this result should be multiplied by 0.85. For pediatric patients, the modified Schwartz equation may be used. The formula is based on height in cm and Scr in mg/dL where k is a constant. Ccr is corrected to 1.73 m² body surface area. During the first year of life, the value of k is 0.33 for pre-term babies and 0.45 for term infants. The k is 0.55 for pediatric patients and adolescent girls and 0.7 for adolescent boys. GFR (mL/min/1.73 m²) = (k x Height)/Scr cIf no loading dose administered. dThe doses listed assume average body composition. Maintenance Dosing in Pediatric Patients Less Than 10 Years Old The starting maintenance dose for heart failure in pediatric patients less than 10 years old is based on the lean body weight, renal function, age, and concomitant products [see DRUG INTERACTIONS]. The recommended starting maintenance dose for pediatric patients between 5 and 10 years old with normal renal function is displayed in Table 4. Table 4: Recommended Starting LANOXIN Maintenance Dosage in Pediatric Patients Between 5 and 10 Years Old Age Daily Oral Maintenance Dose, mcg/kg/day Dose Regimen, mcg/kg/dose 5 to 10 years 6.4 – 12.9 3.2 – 6.4 Twice daily The recommended maintenance dose (to be given twice daily) is presented in Table 5. Table 5: Recommended Maintenance Dose (in micrograms given twice daily) of LANOXIN in Pediatric Patients < 10 Years of Agea Based upon Lean Body Weight and Renal Functiona,b Corrected Creatinine Clearancec Lean Body Weight Number of Days Before Steady State Achievedd kg 20 30 40 50 60 lb 44 66 88 110 132 10 mL/min - 62.5 62.5* 125 125 19 20 mL/min 62.5 62.5 125 125 125 16 30 mL/min 62.5 62.5* 125 125 187.5 14 40 mL/min 62.5 62.5* 125 187.5 187.5 13 50 mL/min 62.5 125 125 187.5 187.5 12 60 mL/min 62.5 125 125 187.5 250 11 70 mL/min 62.5 125 187.5 187.5 250 10 80 mL/min 62.5* 125 187.5 187.5 250 9 90 mL/min 62.5* 125 187.5 250 250 8 100 mL/min 62.5* 125 187.5 250 312.5 7 aRecommended are doses to be given twice daily. bThe doses are rounded to the nearest dose possible using whole and/or half LANOXIN tablets. Recommended doses approximately 30 percent lower than the calculated dose are designated with an *. Monitor digoxin levels in patients receiving these initial doses and increase dose if needed c The modified Schwartz equation may be used to estimate creatinine clearance. See footnote b under Table 2. d If no loading dose administered. Monitoring to Assess Safety, Efficacy, and Therapeutic Blood Levels Monitor for signs and symptoms of digoxin toxicity and clinical response. Adjust dose based on toxicity, efficacy, and blood levels. Serum digoxin levels < 0.5 ng/mL have been associated with diminished efficacy, while levels above 2 ng/mL have been associated with increased toxicity without increased benefit. Interpret the serum digoxin concentration in the overall clinical context, and do not use an isolated measurement of serum digoxin concentration as the basis for increasing or decreasing the LANOXIN dose. Serum digoxin concentrations may be falsely elevated by endogenous digoxin-like substances [see DRUG INTERACTIONS]. If the assay is sensitive to these substances, consider obtaining a baseline digoxin level before starting LANOXIN and correct post-treatment values by the reported baseline level. Obtain serum digoxin concentrations just before the next scheduled LANOXIN dose or at least 6 hours after the last dose. The digoxin concentration is likely to be 10% to 25% lower when sampled right before the next dose (24 hours after dosing) compared to sampling 8 hours after dosing (using once-daily dosing). However, there will be only minor differences in digoxin concentrations using twice daily dosing whether sampling is done at 8 or 12 hours after a dose. Switching from Intravenous Digoxin to Oral Digoxin When switching from intravenous to oral digoxin formulations, make allowances for differences in bioavailability when calculating maintenance dosages (see Table 6). Table 6: Comparison of the Systemic Availability and Equivalent Doses of Oral and Intravenous LANOXIN Absolute Bioavailability Equivalent Doses (in micrograms) LANOXIN Tablets 60 -80% 62.5 125 250 500 LANOXIN Intravenous Injection 100% 50 100 200 400 HOW SUPPLIED Dosage Forms And Strengths Tablets: 125 micrograms are yellow, round, scored tablets with “Y3B” imprinted on one side. Tablets: 250 micrograms are white, round, scored tablets with “X3A” imprinted on one side. Storage And Handling LANOXIN (digoxin) Tablets, Scored 125 mcg (0.125 mg): Bottles of 100 with child-resistant cap (NDC 0173-0242-55) and 1,000 (NDC 0173-0242-75); unit dose pack of 100 (NDC 01730242-56). Imprinted with LANOXIN and Y3B (yellow). LANOXIN (digoxin) Tablets, Scored 250 mcg (0.25 mg): Bottles of 100 with child-resistant cap (NDC 0173-0249-55), 1,000 (NDC 0173-0249-75), and 5,000 (NDC 0173-0249-80); unit dose pack of 100 (NDC 0173-0249-5656). Imprinted with LANOXIN and X3A (white). Store at 25°C (77°F); excursions permitted to 15 to 30°C (59 to 86°F) in a dry place and protect from light. Keep out of reach of children. Manufactured for : GlaxoSmithKline Research Triangle Park, NC 27709 by DSM Pharmaceuticals, Inc. Greenville, NC 27834 or GlaxoSmithKline Research Triangle Park, NC 27709. Revised: 08/2012

INDICATIONS Heart Failure: DIGITEK (digoxin tablets) is indicated for the treatment of mild to moderate heart failure. Digoxin increases left ventricular ejection fraction and improves heart failure symptoms as evidenced by exercise capacity and heart failure-related hospitalizations and emergency care, while having no effect on mortality. Where possible, digoxin should be used with a diuretic and an angiotensin-conver ting enzyme inhibitor, but an optimal order for star ting these three drugs cannot be specified. Atrial Fibrillation: DIGITEK (digoxin tablets) is indicated for the control of ventricular response rate in patients with chronic atrial fibrillation. DOSAGE AND ADMINISTRATION General: Recommended dosages of digoxin may require considerable modification because of individual sensitivity of the patient to the drug, the presence of associated conditions, or the use of concurrent medications. In selecting a dose of digoxin, the following factors must be considered: The body weight of the patient. Doses should be calculated based upon lean (i.e., ideal) body weight. The patient's renal function, preferably evaluated on the basis of estimated creatinine clearance. The patient's age. Infants and children require different doses of digoxin than adults. Also, advanced age may be indicative of diminished renal function even in patients with normal serum creatinine concentration (i.e., below 1.5 mg /dL) Concomitant disease states, concurrent medications, or other factors likely to alter the pharmacokinetic or pharmacodynamic profile of digoxin (see PRECAUTIONS). Serum Digoxin Concentrations: In general, the dose of digoxin used should be determined on clinical grounds. However, measurement of serum digoxin concentrations can be helpful to the clinician in determining the adequacy of digoxin therapy and in assigning certain probabilities to the likelihood of digoxin intoxication. About two-thirds of adults considered adequately digitalized (without evidence of toxicit y) have serum digoxin concentrations ranging from 0.8 to 2 ng/mL. However, digoxin may produce clinical benefits even at serum concentrations below this range. About two-thirds of adult patients with clinical toxicit y have serum digoxin concentrations greater than 2 ng/mL. However, since one third of patients with clinical toxicit y have concentrations less than 2 ng/mL, values below 2 ng/mL do not rule out the possibility that a cer tain sign or symptom is related to digoxin therapy. Rarely, there are patients who are unable to tolerate digoxin at serum concentrations below 0.8 ng/mL. Consequently, the serum concentration of digoxin should always be interpreted in the overall clinical context, and an isolated measurement should not be used alone as the basis for increasing or decreasing the dose of the drug. To allow adequate time for equilibration of digoxin between serum and tissue, sampling of serum concentrations should be done just before the next scheduled dose of the drug. If this is not possible, sampling should be done at least 6 to 8 hours after the last dose, regardless of the route of administration or the formulation used. On a once-daily dosing schedule, the concentration of digoxin will be 10% to 25% lower when sampled at 24 verses 8 hours, depending upon the patient's renal function. On a twice-daily dosing schedule, there will be only minor differences in serum digoxin concentrations whether sampling is done at 8 or 12 hour after a dose. If a discrepancy exists between the repor ted serum concentration and the observed clinical response, the clinician should consider the following possibilities: Analytical problems in the assay procedure. Inappropriate serum sampling time. Administration of a digitalis glycoside other than digoxin. Conditions (described in WARNINGS and PRECAUTIONS) causing an alteration in the sensitivity of the patient to digoxin. Serum digoxin concentration may decrease acutely during periods of exercise without any associate change in clinical efficacy due to increased binding of digoxin to skeletal muscle. Heart Failure: Adults: Digitalization may be accomplished by either of two general approaches that vary in dosage and frequency of administration, but reach the same endpoint in terms of total amount of digoxin accumulated in the body. If rapid digitalization is considered medically appropriate, it may be achieved by administering a loading dose based upon projected peak digoxin body stores. Maintenance dose can be calculated as a percentage of the loading dose. More gradual digitalization may be obtained by beginning an appropriate maintenance dose, thus allowing digoxin body stores to accumulate slowly. Steady-state serum digoxin concentrations will be achieved in approximately five half-lives of the drug for the individual patient. Depending upon the patient's renal function, this will take between 1 and 3 weeks. Rapid Digitalization with a Loading Dose: Peak digoxin body stores of 8 to 12 mcg /kg should provide therapeutic effect with minimum risk of toxicit y in most patients with heart failure and normal sinus rhythm. Because of altered digoxin distribution and elimination, projected peak body stores for patients with renal insufficiency should be conservative (i.e., 6 to 10 mcg/kg) [see PRECAUTIONS]. The loading dose should be administered in several por tions, with roughly half the total given as the first dose. Additional fractions of this planned total dose may be given at 6- to 8-hour intervals, with careful assessment of clinical response before each additional dose. If the patient's clinical response necessitates a change from the calculated loading dose of digoxin, then calculation of the maintenance dose should be based upon the amount actually given. A single initial dose of 500 to 750 mcg (0.5 to 0.75 mg) of digoxin tablets usually produces a detectable effect in 0.5 to 2 hours that becomes maximal in 2 to 6 hours. Additional doses of 125 to 375 mcg (0.125 to 0.375 mg) may be given cautiously at 6- to 8- hour intervals until clinical evidence of an adequate effect is noted. The usual amount of digoxin tablets that a 70-kg patient requires to achieve 8 to 12 mcg/kg peak body stores is 750 to 1,250 mcg (0.75 to 1.25 mg). Digoxin Injection is frequently used to achieve rapid digitalization, with conversion to digoxin tablets or Digoxin Solution in Capsules for maintenance therapy. If patients are switched from intravenous to oral digoxin formulations, allowances must be made for differences in bioavailabilit y when calculating maintenance dosages (see table, CLINICAL PHARMACOLOGY). Maintenance Dosing: The doses of digoxin used in controlled trials in patients with heart failure have ranged from 125 to 500 mcg (0.125 to 0.5 mg) once daily. In these studies, the digoxin dose has been generally titrated according to the patient's age, lean body weight, and renal function. Therapy is generally initiated at a dose of 250 mcg (0.25 mg) once daily in patients under age 70 with good renal function, at a dose of 125 mcg (0.125 mg) once daily in patients over age 70 or with impaired renal function, and at a dose of 62.5 mcg (0.0625 mg) in patients with marked renal impairment. Doses may be increased every 2 weeks according to clinical response. In a subset of approximately 1,800 patients enrolled in the DIG trial (wherein dosing was based on an algorithm similar to that in Table 5) the mean (±SD) serum digoxin concentrations at 1 month and 12 months were 1.01 ± 0.47 ng/mL and 0.97 ± 0.43 ng/mL, respectively. The maintenance dose should be based upon the percentage of the peak body stores lost each day through elimination. The following formula has had wide clinical use: Maintenance Dose = Peak Body Stores (i.e., Loading Dose) x % Daily Loss/100 Where: % Daily Loss = 14 + Ccr/5 (Ccr is creatinine clearance, corrected to 70 kg body weight or 1.73 m2 body sur face area.) Table 5 provides average daily maintenance dose requirements of digoxin tablets for patients with heart failure based upon lean body weight and renal function: Table 5: Usual Daily Maintenance Dose Requirements (mcg) of Digoxin for Estimated Peak Body Stores of 10 mcg/kg Corrected Ccr (mL/min per 70 kg)* Lean Body Weight Number of Days Before Steady-State Achieved† kg 50 60 70 80 90 100 lb 110 132 154 176 198 220 0 62.5‡ 125 125 125 187.5 187.5 22 10 125 125 125 187.5 187.5 187.5 19 20 125 125 187.5 187.5 187.5 250 16 30 125 187.5 187.5 187.5 250 250 14 40 125 187.5 187.5 250 250 250 13 50 187.5 187.5 250 250 250 250 12 60 187.5 187.5 250 250 250 375 11 70 187.5 250 250 250 250 375 10 80 187.5 250 250 250 375 375 9 90 187.5 250 250 250 375 500 8 100 250 250 250 375 375 500 7 *Ccr is creatinine clearance, corrected to 70 kg body weight or 1.73 m2 body sur face area. For adults, if only serum creatinine concentrations (Scr) are available, a Ccr (corrected to 70 kg body weight) may be estimated in men as (140-Age)/Scr. For women, this result should be multiplied by 0.85. Note: This equation cannot be used for estimating creatinine clearance in infants or children. †If no loading dose administered. ‡62.5 mcg = 0.0625 mg Example: Based on the above table, a patient in heart failure with an estimated lean body weight of 70 kg and a Ccr of 60 mL/min, should be given a dose of 250 mcg (0.25 mg) daily of digoxin tablets, usually taken after the morning meal. If no loading dose is administered, steady-state serum concentrations in this patient should be anticipated at approximately 11 days. Infants and Children: In general, divided daily dosing is recommended for infants and young children (under age 10). In the newborn period, renal clearance of digoxin is diminished and suitable dosage adjustments must be observed. This is especially pronounced in the premature infant. Beyond the immediate newborn period, children generally require proportionally larger doses than adults on the basis of body weight or body sur face area. Children over 10 years of age require adult dosages in propor tion to their body weight. Some researchers have suggested that infants and young children tolerate slightly higher serum concentrations than do adults. Daily maintenance doses for each age group are given in Table 6 and should provide therapeutic effects with minimum risk of toxicit y in most patients with heart failure and normal sinus rhythm. These recommendations assume the presence of normal renal function: Table 6: Daily Maintenance Doses in Children with Normal Renal Function Age Daily Maintenance Dose (mcg/kg) 2 to 5 years 5 to 10 years Over 10 years 10 to 15 7 to 10 3 to 5 In children with renal disease, digoxin must be carefully titrated based upon clinical response. It cannot be overemphasized that both the adult and pediatric dosage guidelines provided are based upon average patient response and substantial individual variation can be expected. Accordingly, ultimate dosage selection must be based upon clinical assessment of the patient. Atrial Fibrillation: Peak digoxin body stores larger than the 8 to 12 mcg/kg required for most patients with heart failure and normal sinus rhythm have been used for control of ventricular rate in patients with atrial fibrillation. Doses of digoxin used for the treatment of chronic atrial fibrillation should be titrated to the minimum dose that achieves the desired ventricular rate control without causing undesirable side effects. Data are not available to establish the appropriate resting or exercise target rates that should be achieved. Dosage Adjustment When Changing Preparations: The difference in bioavailability between Digoxin injection or Digoxin Solution in Capsules and Digoxin Pediatric Elixir or digoxin tablets must be considered when changing patients from one dosage form to another. Doses of 100 mcg (0.1 mg) and 200 mcg (0.2 mg) of Digoxin Solution in Capsules are approximately equivalent to 125-mcg (0.125-mg) and 250-mcg (0.25-mg) doses of digoxin tablets and Pediatric Elixir, respectively. (see table in CLINICAL PHARMACOLOGY: Pharmacokinetics). HOW SUPPLIED DIGITEK® (digoxin tablets, USP) 125 mcg (0.125 mg) are yellow, round tablets, and imprinted with B 145 on the scored side of the tablet. They are available as follows: NDC 62794-145-01......................................bottles of 100 tablets NDC 62794-145-10......................................bottles of 1000 tablets NDC 62794-145-56......................................bottles of 5000 tablets DIGITEK™ (digoxin tablets, USP) 250 mcg (0.25 mg) are white, round tablets, and imprinted with B 146 on the scored side of the tablet. They are avail- able as follows: NDC 62794-146-01......................................bottles of 100 tablets NDC 62794-146-10......................................bottles of 1000 tablets NDC 62794-146-56......................................bottles of 5000 tablets Store at 15° to 25°C (59° to 77°F) in a dry place and protect from light. Dispense in a tight, light-resistant container as defined in the USP. Distributed by: BERTEK PHARMACEUTICALS INC. Sugar Land, TX 77478, USA. Manufactured by: AMIDE PHARMACEUTICAL, INC. 101 East Main Street, Little Falls, NJ 07424., USA. FDA Rev date: n/a

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

OVERDOSE Treatment of Adverse Reactions Produced by Overdosage: Digoxin should be temporarily discontinued until the adverse reaction resolves. Every effor t should also be made to correct factors that may contribute to the adverse reaction (such as electrolyte disturbances or concurrent medications). Once the adverse reaction has resolved, therapy with digoxin may be reinstituted, following a careful reassessment of dose. Withdrawal of digoxin may be all that is required to treat the adverse reaction. However, when the primary manifestation of digoxin overdosage is a cardiac arrhythmia, additional therapy may be needed. If the rhy thm disturbance is a symptomatic bradyarrhy thmia or heart block, consideration should be given to the reversal of toxicit y with DIGIBIND® [Digoxin Immune Fab (Ovine)] (see below), the use of atropine, or the inser tion of a temporar y cardiac pacemaker. However, asymptomatic bradycardia or heart block related to digoxin may require only temporar y withdrawal of the drug and cardiac monitoring of the patient. If the rhythm disturbance is a ventricular arrhy thmia, consideration should be given to the correction of electrolyte disorders, par ticularly if hypokalemia (see below) or hypomagnesemia is present. DIGIBIND® [Digoxin Immune Fab (Ovine)] is a specific antidote for digoxin and may be used to reverse potentially life-threatening ventricular arrhythmias due to digoxin overdosage. Administration of Potassium: Ever y effor t should be made to maintain the serum potassium concentration between 4 and 5.5 mmol/L. Potassium is usually administered orally, but when correction of the arrhythmia is urgent and the serum potassium concentration is low, potassium may be administered cautiously by the intravenous route. The electrocardiogram should be monitored for any evidence of potassium toxicity (e.g., peaking of T waves) and to obser ve the effect on the arrhythmia. Potassium salts may be dangerous in patients who manifest bradycardia or heart block due to digoxin (unless primarily relat- ed to supraventricular tachycardia) and in the setting of massive digitalis overdosage (see Massive Digitalis Overdosage subsection). Massive Digitalis Overdosage: Manifestations of life-threatening toxicit y include ventricular tachycardia or ventricular fibrillation, or progressive bradyarrhythmias, or heart block. The administration of more than 10 mg of digoxin in a previously healthy adult or more than 4 mg in a previously healthy child, or a steady-state serum concentration greater than 10 ng/mL often results in cardiac arrest. DIGIBIND® [Digoxin Immune Fab (Ovine)] should be used to reverse the toxic effects of ingestion of a massive overdose. The decision to administer DIGIBIND® [Digoxin Immune Fab (Ovine)] to a patient who has ingested a massive dose of digoxin but who has not yet manifested life-threatening toxicity should depend on the likelihood that life-threatening toxicity will occur (see above). Patients with massive digitalis ingestion should receive large doses of activated charcoal to prevent absorption and bind digoxin in the gut during enteroenteric recirculation. Emesis or gastric lavage may be indicated especially if ingestion has occurred within 30 minutes of the patient's presentation at the hospital. Emesis should not be induced in patients who are obtunded. If a patient presents more than 2 hours after ingestion or already has toxic manifestations, it may be unsafe to induce vomiting or attempt passage of a gastric tube, because such maneuvers may induce an acute vagal episode that can worsen digitalis-related arrhy thmias. Severe digitalis intoxication can cause a massive shift of potassium from inside to outside the cell, leading to life-threatening hyperkalemia. The administration of potassium supplements in the setting of massive intoxication may be hazardous and should be avoided. Hyperkalemia caused by massive digitalis toxicity is best treated with DIGIBIND® [Digoxin Immune Fab (Ovine)]; initial treatment with glucose and insulin may also be required if hyperkalemia itself is acutely life-threatening. CONTRAINDICATIONS Digitalis glycosides are contraindicated in patients with ventricular fibrillation or in patients with a known hypersensitivity to digoxin. A hypersensitivity reaction to other digitalis preparations usually constitutes a contraindication to digoxin.

SIDE EFFECTS The following adverse reactions are included in more detail in the WARNINGS AND PRECAUTIONS section of the label: Cardiac arrhythmias [see WARNINGS AND PRECAUTIONS] Digoxin Toxicity [see WARNINGS AND PRECAUTIONS] Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice. In general, the adverse reactions of LANOXIN are dose-dependent and occur at doses higher than those needed to achieve a therapeutic effect. Hence, adverse reactions are less common when LANOXIN is used within the recommended dose range, is maintained within the therapeutic serum concentration range, and when there is careful attention to concurrent medications and conditions. In the DIG trial (a trial investigating the effect of digoxin on mortality and morbidity in patients with heart failure), the incidence of hospitalization for suspected digoxin toxicity was 2% in patients taking LANOXIN compared to 0.9% in patients taking placebo [see Clinical Studies]. The overall incidence of adverse reactions with digoxin has been reported as 5 to 20%, with 15 to 20% of adverse events considered serious. Cardiac toxicity accounts for about one-half, gastrointestinal disturbances for about one-fourth, and CNS and other toxicity for about one-fourth of these adverse events. Gastrointestinal: In addition to nausea and vomiting, the use of digoxin has been associated with abdominal pain, intestinal ischemia, and hemorrhagic necrosis of the intestines. CNS: Digoxin can cause headache, weakness, dizziness, apathy, confusion, and mental disturbances (such as anxiety, depression, delirium, and hallucination). Other: Gynecomastia has been occasionally observed following the prolonged use of digoxin. Thrombocytopenia and maculopapular rash and other skin reactions have been rarely observed. DRUG INTERACTIONS Digoxin has a narrow therapeutic index, increased monitoring of serum digoxin concentrations and for potential signs and symptoms of clinical toxicity is necessary when initiating, adjusting, or discontinuing drugs that may interact with digoxin. Prescribers should consult the prescribing information of any drug which is co-prescribed with digoxin for potential drug interaction information. P-Glycoprotein (PGP) Inducers/Inhibitors Digoxin is a substrate of P-glycoprotein. Drugs that induce or inhibit P-glycoprotein in intestine or kidney have the potential to alter digoxin pharmacokinetics. Pharmacokinetic Drug Interactions Digoxin concentrations increased > 50% Digoxin Serum Concentration Increase Digoxin AUC Increase Recommendations Amiodarone 70% NA Measure serum digoxin concentrations before initiating concomitant drugs. Reduce digoxin concentrations by decreasing dose by approximately 30% to 50% or by modifying the dosing frequency and continue monitoring. Captopril 58% 39% Clarithromycin NA 70% Dronedarone NA 150% Gentamicin 129 – 212% NA Erythromycin 100% NA Itraconazole 80% NA Nitrendipine 57% 15% Propafenone NA 60-270% Quinidine 100% NA Ranolazine 50% NA Ritonavir NA 86% Tetracycline 100% NA Verapamil 50-75% NA Digoxin concentrations increased < 50% Atorvastatin 22% 15% Measure serum digoxin concentrations before initiating concomitant drugs. Reduce digoxin concentrations by decreasing the dose by approximately 15% to 30% or by modifying the dosing frequency and continue monitoring. Carvedilol 16% 14% Diltiazem 20% NA Indomethacin 40% NA Nefazodone 27% 15% Nifedipine 45% NA Propantheline 24% 24% Quinine NA 33% Saquinavir 27% 49% Spironolactone 25% NA Telmisartan 20-49% NA Tolvaptan 30% NA Trimethoprim 22-28% NA Digoxin concentrations increased, but magnitude is unclear Alprazolam, azithromycin, cyclosporine, diclofenac, diphenoxylate, epoprostenol, esomeprazole, ibuprofen, ketoconazole, lansoprazole, metformin, omeprazole, quinine, rabeprazole, Measure serum digoxin concentrations before initiating concomitant drugs. Continue monitoring and reduce digoxin dose as necessary. Digoxin concentrations decreased Acarbose, activated charcoal, albuterol, antacids, certain cancer chemotherapy or radiation therapy, cholestyramine, colestipol, extenatide, kaolin-pectin, meals high in bran, metoclopramide, miglitol, neomycin, penicillamine, phenytoin, rifampin, St. John's Wort, sucralfate, sulfasalazine Measure serum digoxin concentrations before initiating concomitant drugs. Continue monitoring and increase digoxin dose by approximately 20 % to 40 % as necessary. No significant Digoxin exposure changes Please refer to section 12 for a complete list of drugs which were studies but reported no significant changes on digoxin exposure. No additional actions are required. NA – Not available/reported Potentially Significant Pharmacodynamic Drug Interactions Due to considerable variability of pharmacodynamic interactions, the dosage of digoxin should be individualized when patients receive these medications concurrently. Drugs that Affect Renal Function Caution should be exercised when combining digoxin with any drug that may cause significant deterioration in renal function (e.g., ACE inhibitors, angiotensin receptor blockers, nonsteroidal anti-inflammatory drugs [NSAIDs], COX-2 inhibitors) since a decline in glomerular filtration or tubular secretion may impair the excretion of digoxin. Antiarrthymics Dofetilide Concomitant administration with digoxin was associated with a higher rate of torsades de pointes Sotalol Proarrhythmic events were more common in patients receiving sotalol and digoxin than on either alone; it is not clear whether this represents an interaction or is related to the presence of CHF, a known risk factor for proarrhythmia, in patients receiving digoxin. Dronedarone Sudden death was more common in patients receiving digoxin with dronedarone than on either alone; it is not clear whether this represents an interaction or is related to the presence of advanced heart disease, a known risk factor for sudden death in patients receiving digoxin. Parathyroid Hormone Analog Teriparatide Sporadic case reports have suggested that hypercalcemia may predispose patients to digitalis toxicity. Teriparatide transiently increases serum calcium. Thyroid supplement Thyroid Treatment of hypothyroidism in patients taking digoxin may increase the dose requirements of digoxin. Sympathomimetics Epinephrine Norepinephrine Dopamine Can increase the risk of cardiac arrhythmias Neuromuscular Blocking Agents Succinylcholine May cause sudden extrusion of potassium from muscle cells causing arrhythmias in patients taking digoxin. Supplements Calcium If administered rapidly by intravenous route, can produce serious arrhythmias in digitalized patients. Beta-adrenergic blockers and calcium channel blockers Additive effects on AV node conduction can result in bradycardia and advanced or complete heart block. Drug/Laboratory Test Interactions Endogenous substances of unknown composition (digoxin-like immunoreactive substances, DLIS) can interfere with standard radioimmunoassays for digoxin. The interference most often causes results to be falsely positive or falsely elevated, but sometimes it causes results to be falsely reduced. Some assays are more subject to these failings than others. Several LC/MS/MS methods are available that may provide less susceptibility to DLIS interference. DLIS are present in up to half of all neonates and in varying percentages of pregnant women, patients with hypertrophic cardiomyopathy, patients with renal or hepatic dysfunction, and other patients who are volume-expanded for any reason. The measured levels of DLIS (as digoxin equivalents) are usually low (0.2 to 0.4 ng/mL), but sometimes they reach levels that would be considered therapeutic or even toxic. In some assays, spironolactone, canrenone and potassium canrenoate may be falsely detected as digoxin, at levels up to 0.5 ng/mL. Some traditional Chinese and Ayurvedic medicine substances like Chan Su, Siberian Ginseng, Asian Ginseng, Ashwagandha or Dashen, can cause similar interference. Spironolactone and DLIS are much more extensively protein-bound than digoxin. As a result, assays of free digoxin levels in protein-free ultrafiltrate (which tend to be about 25% less than total levels, consistent with the usual extent of protein binding) are less affected by spironolactone or DLIS. It should be noted that ultrafiltration does not solve all interference problems with alternative medicines. The use of an LC/MS/MS method may be the better option according to the good results it provides, especially in term of specificity and limit of quantization.

SIDE EFFECTS In general, the adverse reactions of digoxin are dose-dependent and occur at doses higher than those needed to achieve a therapeutic effect. Hence, adverse reactions are less common when digoxin is used within the recommended dose range or therapeutic serum concentration range and when there is careful attention to concurrent medications and conditions. Because some patients may be par ticularly susceptible to side effects with digoxin, the dosage of the drug should always be selected carefully and adjust- ed as the clinical condition of the patient warrants. In the past, when high doses of digoxin were used and little attention was paid to clinical status or concurrent medications, adverse reactions to digoxin were more frequent and severe. Cardiac adverse reactions accounted for about one-half, gastrointestinal disturbances for about one-fourth, and CNS and other toxicity for about one-four th of these adverse reactions. However, available evidence suggests that the incidence and severity of digoxin toxicit y has decreased substantially in recent years. In recent controlled clinical trials, in patients with predominantly mild to moderate heart failure, the incidence of adverse experiences was comparable in patients taking digoxin and in those taking placebo. In a large mortality trial, the incidence of hospitalization for suspected digoxin toxicity was 2% in patients taking digoxin compared to 0.9% in patients taking placebo. In this trial, the most common manifestations of digoxin toxicity included gastrointestinal and cardiac disturbances; CNS manifestations were less common. Adults: Cardiac: Therapeutic doses of digoxin may cause heart block in patients with pre-existing sinoatrial or AV conduction disorders; heart block can be avoided by adjusting the dose of digoxin. Prophylactic use of a cardiac pacemaker may be considered if the risk of heart block is considered unacceptable. High doses of digoxin may produce a variet y of rhy thm disturbances, such as first-degree, second-degree (Wenckebach), or third-degree heart block (including asystole); atrial tachycardia with block; AV dissociation; accelerated junctional (nodal) rhy thm; unifocal or multiform ventricular premature contractions (especially bigeminy or trigeminy); ventricular tachycardia; and ventricular fibrillation. Digoxin produces PR prolongation and ST segment depression which should not by themselves be considered digoxin toxicity. Cardiac toxicity can also occur at therapeutic doses in patients who have conditions which may alter their sensitivity to digoxin (see WARNINGS and PRECAUTIONS). Gastrointestinal: Digoxin may cause anorexia, nausea, vomiting and diarrhea. Rarely, the use of digoxin has been associated with abdominal pain, intestinal ischemia, and hemorrhagic necrosis of the intestines. CNS: Digoxin can produce visual disturbances (blurred or yellow vision), headache, weakness, dizziness, apathy, confusion and mental disturbances (such as anxiety, depression, delirium, and hallucination). Other: Gynecomastia has been occasionally observed following the prolonged use of digoxin. Thrombocytopenia and maculopapular rash and other skin reactions have been rarely observed. The following table summarizes the incidence of those adverse experiences listed above for patients treated with digoxin tablets or placebo from two randomized, double-blind, placebo-controlled withdrawal trials. Patients in these trials were also receiving diuretics with or without angiotensin-conver ting enzyme inhibitors. These patients have been stable on digoxin, and were randomized to digoxin or placebo. The results shown in Table 4 reflect the experience in patients following dosage titration with the use of serum digoxin concentrations and careful follow-up. These adverse experiences are consistent with results from a large, placebo-controlled mor talit y trial (DIG trial) wherein over half the patients were not receiving digoxin prior to enrollment. Table 4: Adverse Experiences In Two Parallel, Double-Blind, Placebo-Controlled Withdrawal Trials (Number of Patients Reporting) Digoxin Patients Placebo Patients Adverse Experience (n=123) (n=125) Cardiac Palpitation 1 4 Ventricular extrasystole 1 1 Tachycardia 2 1 Heart arrest 1 1 Gastrointestinal Anorexia 1 4 Nausea 4 2 Vomiting 2 1 Diarrhea 4 1 Abdominal pain 0 6 CNS Headache 4 4 Dizziness 6 5 Mental disturbances 5 1 Other Rash 2 1 Death 4 3 Infants and Children: The side effects of digoxin in infants and children differ from those seen in adults in several respects. Although digoxin may produce anorexia, nausea, vomiting, diarrhea, and CNS disturbances in young patients, these are rarely the initial symptoms of overdosage. Rather, the earliest and most frequent manifestation of excessive dosing with digoxin in infants and children is the appearance of cardiac arrhy thmias, including sinus bradycardia. In children, the use of digoxin may produce any arrhythmia. The most common are conduction disturbances or supraventricular tachyarrhythmias, such as atrial tachycardia (with or without block) and junctional (nodal) tachycardia. Ventricular arrhythmias are less common. Sinus bradycardia may be a sign of impending digoxin intoxication, especially in infants, even in the absence of first degree heart block. Any arrhy thmia or alteration in cardiac conduction that develops in a child taking digoxin should be assumed to be caused by digoxin, until fur ther evaluation proves other wise. DRUG INTERACTIONS Potassium-depleting diuretics are a major contributing factor to digitalis toxicity. Calcium, par ticularly if administered rapidly by the intravenous route, may produce serious arrhythmias in digitalized patients. Quinidine, verapamil, amiodarone, propafenone, indomethacin, itraconazole, alprazolam, and spironolactone raise the serum digoxin concentration due to a reduction in clearance and/or in volume of distribution of the drug, with the implication that digitalis intoxication may result. Erythromycin and clarithromycin (and possibly other macrolide antibiotics) and tetracycline may increase digoxin absorption in patients who inactivate digoxin by bacterial metabolism in the lower intestine, so that digitalis intoxication may result (see CLINICAL PHARMACOLOGY: Absorption). Propantheline and diphenoxylate, by decreasing gut motility, may increase digoxin absorption. Antacids, kaolin-pectin, sulfasalazine, neomycin, cholestyramine, certain anticancer drugs, and metoclopramide may interfere with intestinal digoxin absorption, resulting in unexpectedly low serum concentrations. Rifampin may decrease serum digoxin concentration, especially in patients with renal dysfunction, by increasing the non-renal clearance of digoxin. There have been inconsistent repor ts regarding the effects of other drugs [e.g., quinine, penicillamine] on serum digoxin concentration. Thyroid administration to a digitalized, hypothyroid patient may increase the dose requirement of digoxin. Concomitant use of digoxin and sympathomimetics increases the risk of cardiac arrhythmias. Succinylcholine may cause a sudden extrusion of potassium from muscle cells, and may thereby cause arrhythmias in digitalized patients. Although beta-adrenergic blockers or calcium channel blockers and digoxin may be useful in combination to control atrial fibrillation, their additive effects on AV node conduction can result in advanced or complete heart block. Due to the considerable variability of these interactions, the dosage of digoxin should be individualized when patients receive these medications concurrently. Furthermore, caution should be exercised when combining digoxin with any drug that may cause a significant deterioration in renal function, since a decline in glomerular filtration or tubular secretion may impair the excretion of digoxin. Drug/Laborator y Test Interactions: The use of therapeutic doses of digoxin may cause prolongation of the PR interval and depression of the ST segment on the electrocardiogram. Digoxin may produce false positive ST-T changes on the electrocardiogram during exercise testing. These electrophysiologic effects reflect an expected effect of the drug and are not indicative of toxicity.

WARNINGS Included as part of the PRECAUTIONS section. PRECAUTIONS Ventricular Fibrillation in patients with Accessory AV Pathway (Wolff-Parkinson-White Syndrome) Patients with Wolff-Parkinson-White syndrome who develop atrial fibrillation are at high risk of ventricular fibrillation. Treatment of these patients with digoxin leads to greater slowing of conduction in the atrioventricular node than in accessory pathways, and the risks of rapid ventricular response leading to ventricular fibrillation are thereby increased. Sinus Bradycardia and Sino-atrial Block LANOXIN may cause severe sinus bradycardia or sinoatrial block particularly in patients with pre-existing sinus node disease and may cause advanced or complete heart block in patients with pre-existing incomplete AV block. Consider insertion of a pacemaker before treatment with digoxin Digoxin Toxicity Signs and symptoms of digoxin toxicity include anorexia, nausea, vomiting, visual changes and cardiac arrhythmias [first-degree, second-degree (Wenckebach), or third-degree heart block (including asystole); atrial tachycardia with block; AV dissociation; accelerated junctional (nodal) rhythm; unifocal or multiform ventricular premature contractions (especially bigeminy or trigeminy); ventricular tachycardia; and ventricular fibrillation]. Toxicity is usually associated with digoxin levels > 2ng/ml although symptoms may also occur at lower levels. Low body weight, advanced age or impaired renal function, hypokalemia, hypercalcemia, or hypomagnesemia may predispose to digoxin toxicity. Obtain serum digoxin levels in patients with signs or symptoms of digoxin therapy and interrupt or adjust dose if necessary [see ADVERSE REACTIONS and OVERDOSAGE]. Assess serum electrolytes and renal function periodically. The earliest and most frequent manifestation of digoxin toxicity in infants and children is the appearance of cardiac arrhythmias, including sinus bradycardia. In children, the use of digoxin may produce any arrhythmia. The most common are conduction disturbances or supraventricular tachyarrhythmias, such as atrial tachycardia (with or without block) and junctional (nodal) tachycardia. Ventricular arrhythmias are less common. Sinus bradycardia may be a sign of impending digoxin intoxication, especially in infants, even in the absence of first-degree heart block. Any arrhythmias or alteration in cardiac conduction that develops in a child taking digoxin should initially be assumed to be a consequence of digoxin intoxication. Given that adult patients with heart failure have some symptoms in common with digoxin toxicity, it may be difficult to distinguish digoxin toxicity from heart failure. Misidentification of their etiology might lead the clinician to continue or increase LANOXIN dosing, when dosing should actually be suspended. When the etiology of these signs and symptoms is not clear, measure serum digoxin levels. Decreased Cardiac Output in Patients With Preserved Left Ventricular Systolic Function Patients with heart failure associated with preserved left ventricular ejection fraction may experience decreased cardiac output with use of Lanoxin. . Such disorders include restrictive cardiomyopathy, constrictive pericarditis, amyloid heart disease, and acute cor pulmonale. Patients with idiopathic hypertrophic subaortic stenosis may have worsening of the outflow obstruction due to the inotropic effects of digoxin. Patients with amyloid heart disease may be more susceptible to digoxin toxicity at therapeutic levels because of an increased binding of digoxin to extracellular amyloid fibrils. LANOXIN should generally be avoided in these patients, although it has been used for ventricular rate control in the subgroup of patients with atrial fibrillation. Reduced Efficacy In Patients with Hypocalcemia Hypocalcemia can nullify the effects of digoxin in humans; thus, digoxin may be ineffective until serum calcium is restored to normal. These interactions are related to the fact that digoxin affects contractility and excitability of the heart in a manner similar to that of calcium. Risk of Ventricular Arrhythmias During Electrical Cardioversion It may be desirable to reduce the dose of or discontinue digoxin for 1 to 2 days prior to electrical cardioversion of atrial fibrillation to avoid the induction of ventricular arrhythmias, but physicians must consider the consequences of increasing the ventricular response if digoxin is decreased or withdrawn. If digitalis toxicity is suspected, elective cardioversion should be delayed. If it is not prudent to delay cardioversion, the lowest possible energy level should be selected to avoid provoking ventricular arrhythmias. Altered Response in Thyroid Disorders and Hypermetabolic States Hypothyroidism may reduce the requirements for digoxin. Heart failure and/or atrial arrhythmias resulting from hypermetabolic or hyperdynamic states (e.g., hyperthyroidism, hypoxia, or arteriovenous shunt) are best treated by addressing the underlying condition. Atrial arrhythmias associated with hypermetabolic states are particularly resistant to digoxin treatment. Patients with beri beri heart disease may fail to respond adequately to digoxin if the underlying thiamine deficiency is not treated concomitantly. Risk of Ischemia in Patients With Acute Myocardial Infarction Digoxin is not recommended in patients with acute myocardial infarction because undesirable increases in myocardial oxygen demand and ischemia may result. Vasoconstriction In Patients with Myocarditis Digoxin can precipitate vasoconstriction and may promote production of pro-inflammatory cytokines, therefore should be avoided in patients with myocarditis. Nonclinical Toxicology Carcinogenesis, Mutagenesis, Impairment of Fertility Digoxin showed no genotoxic potential in in vitro studies (Ames test and mouse lymphoma). No data are available on the carcinogenic potential of digoxin, nor have studies been conducted to assess its potential to affect fertility. Use In Specific Populations Pregnancy Pregnancy Category C Digoxin should be given to a pregnant woman only if clearly needed. It is also not known whether digoxin can cause fetal harm when administered to a pregnant woman or can affect reproductive capacity. Animal reproduction studies have not been conducted with digoxin. Labor and Delivery There is not enough data from clinical trials to determine the safety and efficacy of digoxin during labor and delivery. Nursing Mothers Studies have shown that digoxin distributes into breast milk, and that the milk-to-serum concentration ratio is approximately 0.6 to 0.9. However, the estimated exposure of a nursing infant to digoxin via breastfeeding is far below the usual infant maintenance dose. Therefore, this amount should have no pharmacologic effect upon the infant. Nevertheless, caution should be exercised when digoxin is administered to a nursing woman. Pediatric Use The safety and effectiveness of LANOXIN in the control of ventricular rate in children with atrial fibrillation in children have not been established. The safety and effectiveness of LANOXIN in the treatment of heart failure in children have not been established in adequate and well-controlled studies. However, in published literature of children with heart failure due to various etiologies (e.g., ventricular septal defects, anthracycline toxicity, patent ductus arteriosus), treatment with digoxin has been associated with improvements in hemodynamic parameters, and in clinical signs and symptoms. Newborn infants display considerable variability in their tolerance to digoxin. Premature and immature infants are particularly sensitive to the effects of digoxin, and the dosage of the drug must not only be reduced but must be individualized according to their degree of maturity. Geriatric Use The majority of clinical experience gained with digoxin has been in the elderly population. This experience has not identified differences in response or adverse effects between the elderly and younger patients. However, this drug is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, which should be based on renal function, and it may be useful to monitor renal function [see DOSAGE AND ADMINISTRATION]. Renal Impairment The clearance of digoxin can be primarily correlated with the renal function as indicated by creatinine clearance. Tables 2 and 4 provides the usual daily maintenance dose requirements for digoxin based on creatinine clearance (per 70 kg or per 1.73 m) [see DOSAGE AND ADMINISTRATION]. Digoxin is primarily excreted by the kidneys; therefore, patients with impaired renal function require smaller than usual maintenance doses of digoxin [see DOSAGE AND ADMINISTRATION]. Because of the prolonged elimination half-life, a longer period of time is required to achieve an initial or new steady-state serum concentration in patients with renal impairment than in patients with normal renal function. If appropriate care is not taken to reduce the dose of digoxin, such patients are at high risk for toxicity, and toxic effects will last longer in such patients than in patients with normal renal function. Hepatic Impairment Plasma digoxin concentrations in patients with acute hepatitis generally fall within the range of profiles in a group of healthy subjects. Malabsorption The absorption of digoxin is reduced in some malabsorption conditions such as chronic diarrhea.

WARNINGS Sinus Node Disease and AV Block: Because digoxin slows sinoatrial and AV conduction, the drug commonly prolongs the PR interval. The drug may cause severe sinus bradycardia or sinoatrial block in patients with pre-existing sinus node disease and may cause advanced or complete heart block in patients with pre-existing incomplete AV block. In such patients consideration should be given to the inser tion of a pacemaker before treatment with digoxin. Accessory AV Pathway (Wolff-Parkinson-White Syndrome): After intravenous digoxin therapy, some patients with paroxysmal atrial fibrillation or flutter and a coexisting accessory AV pathway have developed increased antegrade conduction across the accessory pathway bypassing the AV node, leading to a very rapid ventricular response or ventricular fibrillation. Unless conduction down the accessory pathway has been blocked (either pharmacologically or by surgery), digoxin should not be used in such patients. The treatment of paroxysmal supraventricular tachycardia in such patients is usually direct-current cardioversion. Use in Patients with Preserved Left Ventricular Systolic Function: Patients with cer tain disorders involving heart failure associated with preser ved left ventricular ejection fraction may be par ticularly susceptible to toxicity of the drug. Such disorders include restrictive cardiomyopathy, constrictive pericarditis, amyloid heart disease, and acute cor pulmonale. Patients with idiopathic hypertrophic subaor tic stenosis may have worsening of the outflow obstruction due to the inotropic effects of digoxin. PRECAUTIONS Use in Patients with Impaired Renal Function: Digoxin is primarily excreted by the kidneys; therefore, patients with impaired renal function require smaller than usual maintenance doses of digoxin (see DOSAGE AND ADMINISTRATION). Because of the prolonged elimination half-life, a longer period of time is required to achieve an initial or new steady-state serum concentration in patients with renal impairment than in patients with normal renal function. If appropriate care is not taken to reduce the dose of digoxin, such patients are at high risk for toxicity, and toxic effects will last longer in such patients than in patients with normal renal function. Use in Patients with Electrolyte Disorders: In patients with hypokalemia or hypomagnesemia, toxicit y may occur despite serum digoxin concentrations below 2 ng/mL, because potassium or magnesium depletion sensitizes the myocardium to digoxin. Therefore, it is desirable to maintain normal serum potassium and magnesium concentrations in patients being treated with digoxin. Deficiencies of these electrolytes may result from malnutrition, diarrhea, or prolonged vomiting, as well as the use of the following drugs or procedures: diuretics, amphotericin B, cor ticosteroids, antacids, dialysis, and mechanical suction of gastrointestinal secretions. Hypercalcemia from any cause predisposes the patient to digitalis toxicity. Calcium, par ticularly when administered rapidly by the intravenous route, may produce serious arrhy thmias in digitalized patients. On the other hand, hypocalcemia can nullify the effects of digoxin in humans; thus, digoxin may be ineffective until serum calcium is restored to normal. These interactions are related to the fact that digoxin affects contractility and excitability of the heart in a manner similar to that of calcium. Use in Thyroid Disorders and Hypermetabolic States: Hypothyroidism may reduce the requirements for digoxin. heart failure and/or atrial arrhy thmias resulting from hypermetabolic or hyperdynamic states (e.g., hyper thyroidism, hypoxia, or ar teriovenous shunt) are best treated by addressing the underly- ing condition. Atrial arrhythmias associated with hypermetabolic states are particularly resistant to digoxin treatment. Care must be taken to avoid toxic- ity if digoxin is used. Use in Patients with Acute Myocardial Infarction: Digoxin should be used with caution in patients with acute myocardial infarction. The use of inotrop- ic drugs in some patients in this setting may result in undesirable increases in myocardial oxygen demand and ischemia. Use During Electrical Cardioversion: It may be desirable to reduce the dose of digoxin for 1 to 2 days prior to electrical cardioversion of atrial fibrillation to avoid the induction of ventricular arrhythmias, but physicians must consider the consequences of increasing the ventricular response if digoxin is withdrawn. If digitalis toxicit y is suspected, elective cardioversion should be delayed. If it is not prudent to delay cardioversion, the lowest possible energy level should be selected to avoid provoking ventricular arrhythmias. Laboratory Test Monitoring: Patients receiving digoxin should have their serum electroly tes and renal function (serum creatinine concentrations) assessed periodically; the frequency of assessments will depend on the clinical setting. For discussion of serum digoxin concentrations, see DOSAGE AND ADMINISTRATION section. Carcinogenesis, Mutagenesis, Impairment of Fertility: There have been no long-term studies performed in animals to evaluate carcinogenic potential, nor have studies been conducted to assess the mutagenic potential of digoxin or its potential to affect fertility. Pregnancy: Teratogenic Effects: Pregnancy Category C. Animal reproduction studies have not been conducted with digoxin. It is also not known whether digoxin can cause fetal harm when administered to a pregnant woman or can affect reproductive capacity. Digoxin should be given to a pregnant woman only if clearly needed. Nursing Mothers: Studies have shown that digoxin concentrations in the mother's serum and milk are similar. However, the estimated exposure of a nursing infant to digoxin via breast feeding will be far below the usual infant maintenance dose. Therefore, this amount should have no pharmacologic effect upon the infant. Never theless, caution should be exercised when digoxin is administered to a nursing woman. Pediatric Use: Newborn infants display considerable variability in their tolerance to digoxin. Premature and immature infants are particularly sensitive to the effects of digoxin, and the dosage of the drug must not only be reduced but must be individualized according to their degree of maturity. Digitalis glycosides can cause poisoning in children due to accidental ingestion. Geriatric Use: The majority of clinical experience gained with digoxin has been in the elderly population. This experience has not identified differences in response or adverse effects between the elderly and younger patients. However, this drug is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, which should be based on renal function, and it may be useful to monitor renal function (see DOSAGE AND ADMINISTRATION).