Digoxin

1 INDICATIONS AND USAGE Digoxin Tablets are a cardiac glycoside indicated for: • Treatment of mild to moderate heart failure in adults. ( 1.1 ) • Increasing myocardial contractility in pediatric patients with heart failure. ( 1.2 ) • Control of resting ventricular rate in patients with chronic atrial fibrillation in adults. ( 1.3 ) 1.1 Heart Failure in Adults Digoxin Tablets are indicated for the treatment of mild to moderate heart failure in adults. Digoxin Tablets increase left ventricular ejection fraction and improve 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, Digoxin Tablets should be used in combination with a diuretic and an angiotensin-converting enzyme (ACE) inhibitor. 1.2 Heart Failure in Pediatric Patients Digoxin Tablets increase myocardial contractility in pediatric patients with heart failure. 1.3 Atrial Fibrillation in Adults Digoxin Tablets are indicated for the control of ventricular response rate in adult 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 toxicity) have serum digoxin concentrations ranging from 0.8 to 2.0 ng/mL. However, digoxin may produce clinical benefits even at serum concentrations below this range. About two-thirds of adult patients with clinical toxicity have serum digoxin concentrations greater than 2.0 ng/mL. However, since one-third of patients with clinical toxicity have concentrations less than 2.0 ng/mL, values below 2.0 ng/mL do not rule out the possibility that a certain 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 versus 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 hours after a dose. If a discrepancy exists between the reported 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 associated 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 bod …

3 DOSAGE FORMS AND STRENGTHS Unscored Tablets: 62.5 mcg are peach colored, round shaped, flat faced, beveled edge, uncoated tablets debossed with ‘D’ and ‘62’ on one side and plain on the other side. Scored Tablets: 125 mcg are white to off-white, round shaped, flat faced, beveled edge, scored, uncoated tablets debossed with “D” "125" (“D” above the score and "125" below the score) on one side and plain on the other side. Scored Tablets: 250 mcg are white to off-white, round shaped, biconvex, scored, uncoated tablets, debossed with “D” “250” (“D” above the score and “250” below the score) on one side and plain on the other side. Unscored Tablets: 62.5 mcg. Scored Tablets: 125 mcg and 250 mcg ( 3 )

4 CONTRAINDICATIONS Digoxin is contraindicated in patients with: • Ventricular fibrillation [see Warnings and Precautions (5.1)] • Known hypersensitivity to digoxin (reactions seen include unexplained rash, swelling of the mouth, lips or throat or a difficulty in breathing). A hypersensitivity reaction to other digitalis preparations usually constitutes a contraindication to digoxin. • Ventricular fibrillation. ( Error! Hyperlink reference not valid. ) • Known hypersensitivity to digoxin or other forms of digitalis. ( 4 )

ADVERSE REACTIONS 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 particularly susceptible to side effects with digoxin, the dosage of the drug should always be selected carefully and adjusted 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-fourth of these adverse reactions. However, available evidence suggests that the incidence and severity of digoxin toxicity 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 variety of rhythm disturbances, such as 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. 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. Table 4 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-converting enzyme inhibitors. These patients had 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 mortality trial (DIG trial) wherein over half the patients were not receiving digoxin prior to enrollment. Table 4: Adverse Experiences …

7 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. PGP Inducers/Inhibitors: Drugs that induce or inhibit PGP have the potential to alter digoxin pharmacokinetics. ( 7.1 ) The potential for drug-drug interactions must be considered prior to and during drug therapy. See full prescribing information. ( 7.2 , 7.3 , 12.3 ) 7.1 P-Glycoprotein (PGP) Inducers/Inhibitors Digoxin is a substrate of P-glycoprotein, at the level of intestinal absorption, renal tubular section and biliary-intestinal secretion. Therefore, drugs that induce/inhibit P-glycoprotein have the potential to alter digoxin pharmacokinetics. 7.2 Pharmacokinetic Drug Interactions Digoxin concentrations increased greater than 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% to 212% NA Erythromycin 100% NA Itraconazole 80% NA Lapatinib NA 180% Propafenone NA 60% to 270% Quinidine 100% NA Ranolazine 50% NA Ritonavir NA 86% Telaprevir 50% 85% Tetracycline 100% NA Verapamil 50% to 75% NA Digoxin concentrations increased less than 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% Conivaptan 33% 43% Diltiazem 20% NA Indomethacin 40% NA Mirabegron 29% 27% Nefazodone 27% 15% Nifedipine 45% NA Propantheline 24% 24% Quinine NA 33% Rabeprazole 29% 19% Saquinavir 27% 49% Spironolactone 25% NA Telmisartan 20% to 49% NA Ticagrelor 31% 28% Tolvaptan 30% 20% Trimethoprim 22% to 28% NA Digoxin concentrations increased, but magnitude is unclear Alprazolam, azithromycin, cyclosporine, diclofenac, diphenoxylate, epoprostenol, esomeprazole, ibuprofen, ketoconazole, lansoprazole, metformin, omeprazole 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 and sulfasalazine Measure serum digoxin concentrations before initiating concomitant drugs. Continue monitoring and increase digoxin dose by approximately 20% to 40% as necessary. NA – Not available/reported 7.3 Potentially Significant Pharmacodynamic Drug Interactions Because of considerable variability of pharmacodynamic interactions, the dosage of digoxin should be individualized when patients receive these medications concurrently. Drugs that Affect Renal Function A decline in GFR or tubular secretion, as from ACE inhibitors, angiotensin receptor blockers, nonsteroidal anti-inflammatory drugs [NSAIDS], COX-2 inhibitors may impair the excretion of digoxin. Antiarrhythmics 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 d …

8 USE IN SPECIFIC POPULATIONS Pregnant patients: It is unknown whether use during pregnancy can cause fetal harm. ( 8.1 ) Pediatric patients: Newborn infants display variability in tolerance to digoxin tablets. ( 8.4 ) Geriatric patients: Consider renal function in dosage selection, and carefully monitor for side effects. ( 8.5 ) Renal impairment: Digoxin tablets are excreted by the kidneys. Consider renal function during dosage selection. ( 8.6 ) 8.1 Pregnancy Risk Summary Experience with digoxin in pregnant women over several decades, based on published retrospective clinical studies and case reports, has not led to the identification of a drug associated risk of major birth defects, miscarriage or adverse maternal and fetal outcomes. Untreated underlying maternal conditions, such as heart failure and atrial fibrillation, during pregnancy pose a risk to the mother and fetus (see Clinical Consideration ) . Animal reproduction studies have not been conducted with digoxin. The estimated background risk of major birth defects and miscarriage for the indicated population(s) are unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively. Clinical Considerations Disease-associated maternal and/or embryo/fetal risk Pregnant women with heart failure are at increased risk for preterm birth. Clinical classification of heart disease may worsen with pregnancy and lead to maternal or fetal death. Pregnant women with atrial fibrillation are at an increased risk of delivering a low birth weight infant. Atrial fibrillation may worsen with pregnancy and can lead to maternal or fetal death. Fetal/neonatal adverse reactions Digoxin has been shown to cross the placenta and is found in amniotic fluid. Monitor neonates for signs and symptoms of digoxin toxicity, including vomiting, and cardiac arrhythmias [see Warnings and Precautions (5.3) ]. Dose adjustments during pregnancy and the postpartum period Digoxin requirements may increase during pregnancy and decrease in the postpartum period. Monitor serum digoxin levels during pregnancy and the postpartum period [see Dosage and Administration (2.5) ]. Labor or Delivery Risk of arrhythmias may increase during the labor and delivery. Monitor patients continuously during labor and delivery [see Warnings and Precautions (5.1 and 5.2) ]. 8.2 Lactation Risk Summary The digoxin dose received through breastfeeding is up to 4% of the neonatal maintenance dosage, which is unlikely to be clinically relevant. There are no data on the effects of digoxin on the breastfed infant or the effects on milk production. Data Based on data from two lactation studies in a total of 13 breastfed infants, the digoxin concentrations in breast milk were between 0.4 ng/mL to 1.0 ng/mL following 0.25 mg once daily dose of digoxin in the lactating mother. Thus, the amount of digoxin ingested daily by the infants is estimated to be between 0.03 to 0.16 mcg/kg/day. This translates to a relative infant dose of digoxin between 1% to 7% of the maternal weight-adjusted dose and about 0.2% to 4% of the neonatal maintenance dose. 8.4 Pediatric Use The safety and effectiveness of digoxin tablets in the control of ventricular rate in children with atrial fibrillation have not been established. The safety and effectiveness of digoxin tablets 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 of 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. Premat …

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 arterial 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 activity may be an important factor in digitalis toxicity.

11 DESCRIPTION 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 2 portions: a sugar and a cardenolide (hence “glycosides”). Digoxin is described chemically as 3β-[( 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]-12β,14-dihydroxy-5β-card-20(22)-enolide. Its molecular formula is C 41 H 64 O 14 , its molecular weight is 780.94, and its structural formula is: Digoxin occurs as white or almost white powder, or colorless 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. Digoxin Tablets, USP are supplied as 125 mcg or 250 mcg tablets for oral administration. Each tablet contains the labeled amount of Digoxin, USP and the following inactive ingredients: 125 mcg: anhydrous lactose, colloidal silicon dioxide, corn starch, D&C yellow #10 aluminum lake, FD&C yellow #6 aluminum lake, lactose monohydrate, magnesium stearate, and starch 1500. 250 mcg: anhydrous lactose, colloidal silicon dioxide, corn starch, lactose monohydrate, magnesium stearate, and starch 1500. digoxin-structural-from-usp-monograph-08-30-2023

10 OVERDOSAGE 10.1 Signs and Symptoms in Adults and Children The signs and symptoms of toxicity are generally similar to those described in the Adverse Reactions (6.1) but may be more frequent and can be more severe. Signs and symptoms of digoxin toxicity become more frequent with levels above 2 ng/mL. However, in deciding whether a patient's symptoms are due to digoxin, the clinical state together with serum electrolyte levels and thyroid function are important factors [see Dosage and Administration (2) ] . Adults: The most common signs and symptoms of digoxin toxicity are nausea, vomiting, anorexia, and fatigue that occur in 30% to 70% of patients who are overdosed. Extremely high serum concentrations produce hyperkalemia especially in patients with impaired renal function. Almost every type of cardiac arrhythmia has been associated with digoxin overdose and multiple rhythm disturbances in the same patient are common. Peak cardiac effects occur 3 to 6 hours following ingestion and may persist for 24 hours or longer. Arrhythmias that are considered more characteristic of digoxin toxicity are new-onset Mobitz type 1 A-V block, accelerated junctional rhythms, non-paroxysmal atrial tachycardia with A-V block, and bi-directional ventricular tachycardia. Cardiac arrest from asystole or ventricular fibrillation is usually fatal. Digoxin toxicity is related to serum concentration. As digoxin serum levels increase above 1.2 ng/mL, there is a potential for increase in adverse reactions. Furthermore, lower potassium levels increase the risk for adverse reactions. In adults with heart disease, clinical observations suggest that an overdose of digoxin of 10 mg to 15 mg results in death of half of patients. A dose above 25 mg ingested by an adult without heart disease appeared to be uniformly fatal if no Digoxin Immune Fab (DIGIBIND ® , DIGIFAB ® ) was administered. Among the extra-cardiac manifestations, gastrointestinal symptoms (e.g., nausea, vomiting, anorexia) are very common (up to 80% incidence) and precede cardiac manifestations in approximately half of the patients in most literature reports. Neurologic manifestations (e.g., dizziness, various CNS disturbances), fatigue, and malaise are very common. Visual manifestations may also occur with aberration in color vision (predominance of yellow green) the most frequent. Neurological and visual symptoms may persist after other signs of toxicity have resolved. In chronic toxicity, non-specific extra-cardiac symptoms, such as malaise and weakness, may predominate. Children: In pediatric patients, signs and symptoms of toxicity can occur during or shortly after the dose of digoxin. Frequent non-cardiac effects are similar to those observed in adults although nausea and vomiting are not seen frequently in infants and small pediatric patients. Other reported manifestations of overdose are weight loss in older age groups, failure to thrive in infants, abdominal pain caused by mesenteric artery ischemia, drowsiness, and behavioral disturbances including psychotic episodes. Arrhythmias and combinations of arrhythmias that occur in adult patients can also occur in pediatric patients although sinus tachycardia, supraventricular tachycardia, and rapid atrial fibrillation are seen less frequently in pediatric patients. Pediatric patients are more likely to develop A-V conduction disturbances, or sinus bradycardia. Any arrhythmia in a child treated with digoxin should be considered related to digoxin until otherwise ruled out. In pediatric patients aged 1 to 3 years without heart disease, clinical observations suggest that an overdose of digoxin of 6 mg to 10 mg would result in death of half of the patients. In the same population, a dose above 10 mg resulted in death if no Digoxin Immune Fab were administered. 10.2 Treatment Chronic Overdose If there is suspicion of toxicity, discontinue digoxin tablets and place the patient on a cardiac monitor. Correct factors such as electrolyte abnormalities, …

16 HOW SUPPLIED/STORAGE AND HANDLING Digoxin Tablets USP, 62.5 mcg are peach colored, round shaped, flat faced, beveled edge, uncoated tablets debossed with ‘D’ and ‘62’ on one side and plain on the other side and are supplied as follows: Bottles of 100 NDC 59651-436-01 Bottles of 1,000 NDC 59651-436-99 Digoxin Tablets USP, 125 mcg are white to off-white, round shaped, flat faced, beveled edge, scored, uncoated tablets debossed with “D” "125" (“D” above the score and "125" below the score) on one side and plain on the other side and are supplied as follows: Bottles of 100 NDC 59651-437-01 Bottles of 1,000 NDC 59651-437-99 Digoxin Tablets USP, 250 mcg are white to off-white, round shaped, biconvex, scored, uncoated tablets, debossed with “D” “250” (“D” above the score and “250” below the score) on one side and plain on the other side and are supplied as follows: Bottles of 100 NDC 59651-438-01 Bottles of 1,000 NDC 59651-438-99 Store at 20° to 25°C (68° to 77°F) [See USP Controlled Room Temperature] in a dry place and protect from light. Keep out of reach of children. Dispense in tight, light-resistant container.