Generic Name: digoxin

Brand Names: Lanoxin, Lanoxicaps

Digoxin is used for treating heart failure and irregular heartbeat. Digoxin helps make your heart beat more regularly and strengthens your heart muscle.

This medicine is also used to treat certain types of rhythm disorders of the heart such as atrial fibrillation, atrial flutter, and AV block (especially second or third-degree AV block).

Digoxin belongs to a class of drugs called cardiac glycosides. It works by affecting certain minerals (sodium and potassium) in the body that are needed for the proper function of the heart.

Do NOT use digoxin if:

you are allergic to any ingredient in digoxin or similar medicines (such as quinidine, procainamide)

Contact your doctor or health care provider right away if any of these apply to you.

Some medical conditions may interact with digoxin. Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you:

if you are pregnant, planning to become pregnant, or are breast-feeding

if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement

if you have allergies to medicines, foods, or other substances

if you have heart rhythm problems other than those listed in this medication guide

if you have a history of certain types of irregular heartbeat such as “sick sinus syndrome” or “AV block” (unless you have a pacemaker)

if you have low blood levels of potassium or magnesium

if you have a history of liver disease, kidney disease, thyroid problems, or parathyroid gland disorder

if you are taking certain medicines such as digitalis, quinidine, or procainamide.

Drug Interactions

Digoxin is metabolized in the liver via conjugation with glucuronic acid. Drugs that inhibit hepatic microsomal enzymes may increase plasma concentrations of digoxin. Examples of such drugs include erythromycin, diltiazem, verapamil, quinidine, fluoxetine, and paroxetine.

Concomitant administration of digoxin and digitalis glycosides may result in increased plasma concentrations of both drugs. Therefore, close monitoring of serum drug concentrations is recommended when these agents are used together.

Pharmacokinetics

Absorption:

Digoxin is rapidly and completely absorbed from the GI tract after oral administration; however, peak plasma concentrations are delayed for about 6 hours. Food decreases the rate but not the extent of absorption.

Distribution:

After oral administration, digoxin is widely distributed throughout the body with a volume of distribution of approximately 4 L/kg. Digoxin crosses the placenta and is distributed into breast milk. Plasma protein binding ranges from 25% to 40%.

Metabolism and Excretion:

Digoxin is metabolized in the liver via conjugation with glucuronic acid and excreted by the kidney. The half-life of digoxin is generally 24 to 48 hours; however, in patients with renal impairment, the half-life may be prolonged to 72 hours or longer. Excretion of digoxin is decreased in patients with congestive heart failure.

Indications and Usage for Digoxin

Digoxin is indicated for the treatment of mild to moderate congestive heart failure (CHF) and management of associated ventricular arrhythmias. In CHF, digoxin increases myocardial contractility (positive inotropic effect) without increasing myocardial oxygen demand. The positive inotropic effect is due primarily to enhanced cardiac muscle cell membrane sodium-potassium ATPase activity and increased calcium uptake by the sarcoplasmic reticulum. The net result is an increase in cardiac output and a decrease in ventricular filling pressures.

The use of digoxin alone or in combination with other agents for the treatment of CHF has been associated with an improvement in symptoms, weight loss, and exercise tolerance; however, data from large clinical trials have failed to demonstrate a mortality benefit.

Digoxin is also indicated for the management of atrial fibrillation and flutter. In both arrhythmias, digoxin decreases automaticity and conduction velocity while having little effect on refractoriness. The result is a decrease in heart rate and, in atrial fibrillation, a reduction in the risk of thromboembolic complications.

Contraindications

Digoxin is contraindicated in patients with known hypersensitivity to the drug and in patients with ventricular fibrillation or ventricular tachycardia. Digoxin is also contraindicated in patients with severe bradycardia (<40 bpm) unless a functioning artificial pacemaker is present.

Side Effects

The most common side effects of digoxin are gastrointestinal in nature and include anorexia, nausea, vomiting, and diarrhea. These side effects are usually mild and resolve with continued therapy.

Digoxin may also cause cardiac arrhythmias, which can be serious or fatal. Arrhythmias associated with digoxin therapy include atrial fibrillation, atrial flutter, ventricular tachycardia, and ventricular fibrillation. Digoxin may also cause heart block, which can be serious or fatal.

Other less common side effects of digoxin include headache, dizziness, blurred vision, confusion, depression, and hallucinations. These side effects are usually reversible with discontinuation of therapy.

Serious side effects, including cardiac arrhythmias and heart block, may be more common in elderly patients.

Dosage and Administration

Digoxin is available in tablet, elixir, and injectable forms. The usual starting dose of digoxin is 0.125 mg daily. The dose may be increased by 0.125 mg every 2 to 4 weeks until the desired clinical effect is achieved or side effects become unacceptable. The usual maintenance dose is 0.25 to 0.5 mg daily.

In patients with atrial fibrillation or flutter, the usual starting dose of digoxin is 0.25 mg daily. The dose may be increased by 0.25 mg every 2 to 4 weeks until the desired clinical effect is achieved or side effects become unacceptable. The usual maintenance dose is 0.5 to 1 mg daily.

Overdose

Symptoms of digoxin toxicity include anorexia, nausea, vomiting, diarrhea, visual disturbances (e.g., halos around lights), headache, dizziness, confusion, depression, and hallucinations. Cardiac toxicity may manifest as bradycardia, heart block, atrial or ventricular arrhythmias, or sudden death.

Treatment of digoxin overdose includes removal of the drug from the body (e.g., gastric lavage, activated charcoal) and supportive measures to treat manifestations of toxicity. Intravenous administration of Fab Fragments (Digibind) is indicated for serious or life-threatening arrhythmias. Plasma concentrations of digoxin should be monitored closely and maintained in the therapeutic range.

Monitoring

Therapeutic effect – Therapeutic effects of digoxin include a reduction in heart rate and, in atrial fibrillation, a reduction in the risk of thromboembolic complications.

Toxicity – Toxicity may manifest as gastrointestinal upset, visual disturbances, cardiac arrhythmias, or heart block. Plasma concentrations of digoxin should be monitored closely and maintained in the therapeutic range. Electrocardiography should be performed regularly to detect arrhythmias.

Storage

Digoxin tablets should be stored at room temperature, 15 C to 30 C (59 F to 86 F).

Digoxin elixir should be stored in the refrigerator, 2 C to 8 C (36 F to 46 F).

Digoxin injection should be stored at room temperature, 15 C to 30 C (59 F to 86 F).