Pharmacokinetics of conventional and slow-release verapamil.
Verapamil is a racemic mixture of two optical isomers, the (-)-form being the more active component. Recent studies indicate a rapid hepatic transformation of (-)-verapamil, which results in different concentration-effect relationships after oral and intravenous administration. In practice the important pharmacokinetic properties of verapamil are low bioavailability (20%), predominant elimination by metabolism (greater than 95%) and a relatively short half-life (t1/2, beta is 3-5 h). After repeated dosing, the rate of hepatic drug clearance seems to decrease. Slow release (SR) formulations of verapamil may offer certain therapeutic advantages during long-term treatment. A comparison of conventional (C) and SR tablets in a 1-week treatment of eight cardiac patients showed a relative bioavailability (AUCSR/AUCC) of 90 +/- 30%. More stable serum drug levels were maintained by 12-hourly administration of SR verapamil. A further study using a new 240 mg SR preparation in patients with arterial hypertension showed that even a single daily dose can be sufficient for adequate blood pressure control over 24 h.
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003692:Delayed-Action Preparations; D006801:Humans; D006973:Hypertension / Q000188:drug therapy; D007700:Kinetics; D008875:Middle Aged; D014700:Verapamil / Q000008:administration & dosage / Q000378:metabolism* / Q000627:therapeutic use
D003692:Delayed-Action Preparations; D014700:Verapamil