Digoxin

Digoxin is a cardiac glycoside used to treat heart failure and regulate heart rate in atrial fibrillation. Digoxin is the nature found in foxglove (digitalis purpurea).

Indications

In heart failure, digoxin helps the heart to contract more powerfully and pump more blood round the body. Although digoxin reduces the need for hospital admissions it has no effect on mortality. There are other heart failure drugs with proven mortality benefit, such as ACE inhibitors, beta blockers and aldosterone antagonists, which should therefore be used before digoxin is considered.

In atrial fibrillation and to a limited extent in atrial flutter, digoxin slows down and regulates heart rate which helps to increase the pumping efficacy of the heart and reduce symptoms of palpitations. However, digoxin used alone works mainly in people with limited mobility and has less effect on fast heart rate on exertion or stress, therefore beta blockers or bradycardising calcium channel blockers diltiazem and verapamil should be the first choice in atrial fibrillation. Digoxin is often used in conjunction with beta blockers and diltiazem. The strongest indication for digoxin is in patients with both heart failure and atrial fibrillation.

Digoxin has relatively long half-life and therefore somewhat higher doses are sometimes used for loading at the beginning of treatment. After that, the dose is reduced to usually 125 mcg or 250 mcg daily. The dose of digoxin depends on patient's size, age and kidney function. Digoxin may interact with other medications, e.g. with antibiotic erythromycin and with verapamil and amiodarone which are also often used in treatment of arrhythmias.

Adverse effects

Digoxin is normally well tolerated but side effects are not unusual due to its narrow margin between effectiveness and toxicity. Common adverse effects are nausea, vomiting and diarrhea, confusion and drowsiness. Arrhythmias can occur especially in presence of low level of potassium in blood.

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