Digoxin is a kind of medicine used to treat heart failure and disturbances in the rhythm of the heart. It is a purified cardiac glycoside, which means it belongs to a group of drugs, commonly referred to as digitalis, containing potentially poisonous substances extracted from the common foxglove plant. Digoxin is one example of what are known as inotropic agents, which are drugs that directly affect the contraction of heart muscle. Its action on heart muscle results in an increase in the force of contraction, raising the output of a failing heart. In conditions where the heartbeat is irregular, digoxin can help by slowing and steadying the rhythm.
Cardiac glycosides such as digoxin have been used in the form of plant extracts since ancient Egyptian times, sometimes being employed as medicines and sometimes, in higher doses, as poisons. In the treatment of heart failure, the use of digoxin is generally reserved for patients who also have a disorder known as atrial fibrillation, where the upper chambers of the heart beat too quickly and in an irregular manner. It is also used sometimes in cases of severe heart failure where other drugs have not worked.
In another disorder which disturbs the heart rhythm, known as supraventricular tachycardia, an area of heart tissue above the lower chambers, or ventricles, overrides the normal pacemaker tissue of the heart causing sudden bursts of a fast but regular heartbeat to occur. This may cause symptoms such as palpitations, dizziness and breathlessness. The symptoms may be mild enough to live with, but if not, treatment with digoxin may be beneficial. A treatment called catheter ablation is sometimes used instead of medication, with a wire being passed into the heart and a current sent along it to destroy areas of abnormal pacemaker tissue.
Some people may have atrial fibrillation without heart failure, and the fast, random heart rate may lead to symptoms of chest pain and palpitations, as well as feeling dizzy and short of breath. Atrial fibrillation can increase a person's risk of experiencing a stroke. For this heart condition, treatment with digoxin is one option, but other drugs are more commonly used along with medication to prevent blood clotting and electrical cardioversion, a technique where electric shocks are used to restore the heart's normal rhythm.
Digoxin can cause adverse effects such as a disturbed heart rate, nausea, blurred vision, dizziness and diarrhea. People with a low tolerance of the drug are more at risk of experiencing these toxic effects. Low tolerance is more frequently found in the elderly, people with hypothyroidism, where the thyroid gland is underactive, and, most commonly, patients undergoing treatment with diuretic drugs who may have low potassium levels. In mild cases of toxicity, the drug is simply withdrawn, but in more severe cases the stomach is washed out and intravenous fluids are given together with medication to regularize the heart rate.