Digoxin

Abstract

Digoxin is a glycoside obtained from the leaves of Digitalis lanata. It is used in cardiac failure to increase the force of myocardial contraction and in supra-ventricular arrhythmias where use is made of its ability to reduce the conductivity of the heart. Side-effects during therapy are common because of the narrow margin between therapeutic and toxic doses, the therapeutic range in plasma being 0.5-2.0 ng/ml. Digoxin binds strongly to tissues such as skeletal and cardiac muscle with a resulting large volume of distribution and a long half-life in plasma of 20 to 50 hours. Steady-state plasma concentrations take 6 to 7 days to be achieved. Digoxin is excreted largely unchanged by the kidney hence clearance is prolonged by renal impairment. Therapeutic drug monitoring in hospitals has been shown to be cost-effective by reducing the incidence of side-effects and shortening in-patient stay.