One of a number of drugs known as cardiac GLYCOSIDES. They increase the contractility of heart muscle; depress the conducting tissue while increasing myocardial excitability; and increase activity of the VAGUS nerve. Digoxin is usually given orally for the treatment of atrial FIBRILLATION and heart failure. The adverse effects of overdosage (which occur more commonly in people with HYPOKALAEMIA, the elderly, and those with renal failure – see KIDNEYS, DISEASES OF) are vomiting, DYSRHYTHMIAS, muscle weakness, and visual disturbances. The ELECTROCARDIOGRAM has a characteristic appearance. Digoxin has a specific antidote which can be used to counteract significant overdose.