Pharmacokinetics and Electrophysiological Effects of Verapamil in Patients with Paroxysmal Supraventricular Tachycardia

Abstract

Ten mg of verapamil was administered intravenously to eight patients with paroxysmal supraventricular tachycardia. After drug administration, investigation of the pharmacokinetics of verapamil was carried out, and the relationship between plasma verapamil concentration and its electrophysiological effects was studied. After verapamil administration, pharmacokinetic parameters were calculated using a two-compartment open model. Biological half-life ranged from 2.91 to 4.55 hours and apparent volume of distribution ranged from 1.28 to 3.18 L/kg. Total body clearance ranged from 216 to 733 ml/min.
Verapamil significantly prolonged the AH interval but did not prolong the HV interval. The effective and the functional refractory period of the AV node (ERPAVN and FRPAVN) were also prolonged after verapamil administration. The antegrade echo zone and the supraventricular tachycardia zone were also narrowed in most patients. A concentration-dependent relationship between plasma verapamil andpercent increase of both ERPAVN and AH interval was observed.