Cardiac glycosides have important positive inotropic, neurohormonal, and electrophysiologic actions, which are the basis for its use in two clinical situations: heart failure due to systolic dysfunction, and in certain supraventricular tachyarrhythmias. The ability of digoxin to reduce sympathetic activation has also been recognized. For maximal early benefits, digoxin requires loading doses, which can be administered intravenously or orally. (See "Use of digoxin in heart failure due to systolic dysfunction", section on 'Mechanism of action' and "Control of ventricular rate in atrial fibrillation: Pharmacologic therapy", section on 'Digoxin'.)
While two cardiac glycosides (digoxin and digitoxin) were previously used, digitoxin has not been widely available since the 1980s. As digoxin is now the only cardiac glycoside available in most countries, the method of initiating therapy with digoxin is presented here. Recommendations regarding the use of digoxin in the management of heart failure or arrhythmias are discussed separately. (See "Use of digoxin in heart failure due to systolic dysfunction" and "Control of ventricular rate in atrial fibrillation: Pharmacologic therapy", section on 'Digoxin'.)
INITIATION OF THERAPY
The electrolyte and renal status of each patient should be ascertained prior to initiating treatment and periodically thereafter. Hypokalemia or hypomagnesemia, for example, may promote the development of digoxin-induced arrhythmias, while impaired renal function may result in higher than anticipated serum drug levels. (See 'Dose adjustments' below.)
The initiation of digoxin therapy has been divided into rapid and slow digitalization followed by the maintenance digoxin dose, and the proposed regimens vary considerably. The following principles should be viewed as a general guide to the use of digoxin for its inotropic or electrophysiologic effects, which must be modified according to clinical circumstances. Patients receiving digoxin for ventricular rate control in atrial fibrillation or flutter will usually require more rapid loading and higher maintenance doses than those treated with digoxin for heart failure, in whom a loading dose is typically not required. Doses used are smaller and blood levels are lower than those needed for the inotropic effect but are generally sufficient to reduce the sympathetic activation associated with heart failure, the primary mechanism of benefit in heart failure patients.
Rapid digoxin loading — Rapid intravenous and oral digitalization is often used to control the ventricular response in atrial fibrillation and flutter. However, other drugs may be more effective and/or have a more rapid onset of action on the ventricular response in these arrhythmias; therefore, rapid digitalization is rarely needed unless alternative drugs are contraindicated or have not been effective. (See "Control of ventricular rate in atrial fibrillation: Pharmacologic therapy", section on 'Pharmacologic treatment' and "Control of ventricular rate in atrial flutter", section on 'Rate control with drugs'.)