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).
In heart failure, digoxin helps the heart contract more powerfully and pump more blood around the body. Although digoxin reduces the need for hospital admissions, it does not affect mortality. Other heart failure drugs with proven mortality benefit, such as ACE inhibitors, beta-blockers, and aldosterone antagonists, should be used before digoxin is considered.
In atrial fibrillation and to a limited extent in atrial flutter, digoxin reduces 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 a weaker effect on fast heart rate on exertion or stress in physically active patients. 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 a 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 the patient's size, age, and kidney function. Digoxin may interact with other medications, e.g. with antibiotic erythromycin and verapamil and amiodarone, which are often used to treat arrhythmias.
Digoxin is usually well tolerated, but side effects are not unusual due to its narrow margin between effectiveness and toxicity. Common adverse effects are nausea, diarrhoea, vomiting, confusion, and drowsiness. Arrhythmias can occur, especially in the presence of a low level of potassium in the blood.