Digoxin-verapamil interaction

Abstract

To explore a possible interaction between digoxin and verapamil, a single-dose kinetic study of digoxin was performed and then repeated after 10 days of verapamil treatment in 8 healthy subjects. Verapamil diminished the apparent central distribution volume of digoxin from 0.83 .+-. 0.25 to 0.64 .+-. 0.17 l/kg (P < 0.05) and reduced total body clearance of digoxin from 3.28 .+-. 0.58 to 2.15 .+-. 0.66 ml/min per kg (P < 0.001) by impairing both renal and extrarenal clearance. Biological digoxin half-life rose from 38.6 .+-. 8.5 to 50.5 .+-. 8.3 h (P < 0.005). Reduction of renal clearance of digoxin may be due to inhibition of tubular secretion. The underlying mechanisms of extrarenal interaction are not known, but impaired hepatic degradation of digoxin induced by verapamil should be considered.