Pharmacokinetics of verapamil in man

Verapamil was given intravenously (10 mg) and orally (120 mg) in six healthy subjects. After intravenous administration, the serum levels in all subjects declined bi-exponentially. Thereupon, pharmacokinetic parameters were calculated using a two-compartment open model. The half-lives of distribution (T 1/2 alpha) and elimination (T 1/2 beta) phases showed 0.23 hour and 4.21 hour on an average respectively. The apparent volume of distribution [Vd (area)] showed 2.51 1/kg and body clearance (C1b) showed 500.64 ml/min on an average. Renal clearance was smaller than normal human creatinine clearance. After oral administration, the time to reach peak blood level (Tmax) was reached within 1.84 hour and the peak serum concentration showed 219.09 ng/ml on an average. The bioavailability was only 22.47% on an average. Verapamil produced a marked prolongation of PQ interval on electrocardiogram and the degree of PQ interval prolongation was closely related to the increase in serum concentration of this compound. QRS, QTc and RR interval were not changed by this compound.