Augmented Digoxin Concentrations with Carvedilol Dosing in Mild-Moderate Heart Failure

Carvedilol is a partially selective beta-adrenergic blocking agent. Recent clinical studies have suggested that carvedilol may improve left ventricular function and symptoms in patients with heart failure. The effects of carvedilol on serum digoxin levels in subjects with heart failure is unknown. Therefore, 22 New York Heart Association functional class II--III patients with idiopathic dilated cardiomyopathy were studied in a prospective, double-blind, placebo-controlled trial. The patients were selected from a clinical trial evaluating the efficacy and hemodynamic effects of chronic carvedilol treatment in heart failure. Carvedilol administration was associated with a 26% increase in steady-state serum digoxin concentrations versus placebo (p = NS). No patients required digoxin dosage adjustments and there were no clinically significant adverse events directly attributable to an increase of serum digoxin concentration. Thus, clinical significant changes in serum digoxin concentrations are not observed in most patients who receive carvedilol. However, the small increase in serum digoxin concentrations warrants caution be exercised in patients with elevated digoxin concentrations during coadministration of carvedilol.