Digoxin

1 INDICATIONS AND USAGE Digoxin injection is 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 adults with chronic atrial fibrillation. ( 1.3 ) 1.1 Heart Failure in Adults Digoxin injection is indicated for the treatment of mild to moderate heart failure in adults. Digoxin injection 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, digoxin injection should be used in combination with a diuretic and an angiotensin-converting enzyme (ACE) inhibitor. 1.2 Heart Failure in Pediatric Patients Digoxin injection increases myocardial contractility in pediatric patients with heart failure. 1.3 Atrial Fibrillation in Adults Digoxin injection is indicated for the control of ventricular response rate in adult patients with chronic atrial fibrillation.

2 DOSAGE AND ADMINISTRATION Digoxin injection dose is based on patient-specific factors (age, lean body weight, renal function, etc.). See full prescribing information. Monitor for toxicity and therapeutic effect. ( 2 ) Intravenous administration is preferable to intramuscular. Avoid bolus administration. ( 2 ) 2.1 Important Dosing and Administration Information In selecting a digoxin injection 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. Parenteral administration of digoxin should be used only when the need for rapid digitalization is urgent or when the drug cannot be taken orally. Intramuscular injection can lead to severe pain at the injection site, thus intravenous administration is preferred. If the drug must be administered by the intramuscular route, it should be injected deep into the muscle followed by massage. For adults, no more than 500 mcg of digoxin injection should be injected into a single site. For pediatric patients, no more than 200 mcg of digoxin injection should be injected into a single site. Administer the dose over a period of 5 minutes or longer and avoid bolus administration to prevent systemic and coronary vasoconstriction. Mixing of digoxin injection with other drugs in the same container or simultaneous administration in the same intravenous line is not recommended. Digoxin injection can be administered undiluted or diluted with a 4-fold or greater volume of Sterile Water for Injection, 0.9% Sodium Chloride Injection, or 5% Dextrose Injection. The use of less than a 4-fold volume of diluent could lead to precipitation of the digoxin. Immediate use of the diluted product is recommended. Consider interruption or reduction in digoxin injection dose prior to electrical cardioversion [see Warnings and Precautions ( 5.4 )]. Discard unused portion of digoxin injection. 2.2 Loading Dosing Regimen in Adults and Pediatric Patients Table 1. Recommended Digoxin Injection Loading Dose Age Total IV Loading Dose (mcg/kg) Administer half the total loading dose initially, then 1⁄4 the loading dose every 6 to 8 hours twice mcg = microgram Premature 15-25 Full-Term 20-30 1-24 Months 30-50 2-5 Years 25-35 5-10 Years 15-30 Adults and pediatric patients over 10 years 8-12 2.3 Maintenance Dosing in Adults and Pediatric Patients Over 10 Years Old The maintenance dose is based on lean body weight, renal function, age, and concomitant products [see Clinical Pharmacology ( 12.3 )] . The recommended starting maintenance doses in adults and pediatric patients over 10 years old with normal renal function are given in Table 2 . Doses may be increased every 2 weeks according to clinical response, serum drug levels, and toxicity. Table 2. Recommended Starting Digoxin Injection Maintenance Dosage in Adults and Pediatric Patients Over 10 Years Old mcg = microgram Age Total Intravenous Maintenance Dose, mcg/kg/day (given once daily) Adults and pediatric patients over 10 years 2.4-3.6 Table 3 provides the recommended (once daily) maintenance dose for adults and pediatric patients over 10 years old (to be given once daily) 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 digoxin injection 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 micr …

3 DOSAGE FORMS AND STRENGTHS Digoxin injection, USP: Ampules of 500 mcg (0.5 mg) in 2 mL (250 mcg [0.25 mg] per 1 mL). Digoxin injection USP: Ampules containing 500 mcg (0.5 mg) in 2 mL. ( 3 )

4 CONTRAINDICATIONS Digoxin injection 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. ( 4 ) • Known hypersensitivity to digoxin or other forms of digitalis. ( 4 )

6 ADVERSE REACTIONS The following adverse reactions are included in more detail in the Warnings and Precautions section of the label: • Cardiac arrhythmias [see Warnings and Precautions ( 5.1 , 5.2 )] • Digoxin Toxicity [see Warnings and Precautions ( 5.3 )] 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. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Sandoz Inc. at 1-800-525-8747 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . 6.1 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 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, 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 digoxin compared to 0.9% in patients taking placebo [see Clinical Studies ( 14.1 )] . 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.

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 Pharmacokinetic interactions have been observed and reported primarily when digoxin is co-administered by oral route. There are very few studies that have evaluated the drug interaction when digoxin is administered via IV route. The magnitude of digoxin exposure change through IV route is generally lower than that through oral route. Table below provides available interaction data using digoxin IV formulation (NA means not available). Digoxin concentrations increased greater than 50% Digoxin Serum Concentration Increase Digoxin AUC Increase Recommendations Quinidine NA 54-83% 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. Ritonavir NA 86% Digoxin concentrations increased less than 50% Amiodarone 17% 40% 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. Propafenone 28% 29% Quinine NA 34-38% Spironolactone NA 44% Verapamil NA 24% Mirabegron 29% 27% 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. 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 produc …

8 USE IN SPECIFIC POPULATIONS • Pediatric patients: Newborn infants display variability in tolerance to digoxin. ( 8.4 ) • Geriatric patients: Consider renal function in dosage selection, and carefully monitor for side effects. ( 8.5 ) • Renal impairment: Digoxin is 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 2-4% and 15-20%, 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 – 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 in the control of ventricular rate in children with atrial fibrillation have not been established. The safety and effectiveness of digoxin 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. Premature and immature infants are particularly sensitive to the effects of digoxin, and the dosage of the drug must not only be reduced but …

12.1 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).

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,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-ribo -hexopyranosyl)oxy]-12,14-dihydroxy-card-20(22)-enolide. Its molecular formula is C 41 H 64 O 14 , its molecular weight is 780.95, and its structural formula is: Digoxin exists as clear to white odorless crystals or white, odorless crystalline powder that melts 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 injection, USP is a sterile solution of digoxin for intravenous or intramuscular injection. Each mL contains: digoxin 0.25 mg, propylene glycol 40% (v/v), anhydrous ethanol 10% (v/v), dibasic sodium phosphate 0.3% (w/v) and anhydrous citric acid 0.08% (w/v) to adjust pH between 6.8 and 7.2, and water for injection. Dilution is not required. digoxin-chemical-structure

10 OVERDOSAGE 10.1 Signs and Symptoms in Adults and Children The signs and symptoms of toxicity are generally similar to those previously described [see 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 increases the risk for adverse reactions. In adults with heart disease, clinical observations suggest that an overdose of digoxin of 10 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, nonspecific 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 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 and place the patient on a cardiac monitor. Correct factors such as electrolyte abnormalities, thyroid …

16 HOW SUPPLIED/STORAGE AND HANDLING Digoxin Injection, USP 500 mcg (0.5 mg) in 2 mL (250 mcg [0.25 mg] per mL) is available as follows: NDC 0781-3059-95 ampules of 2 mL in boxes of 10 Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature] and protect from light. Discard unused portion.