We applied physiologically based pharmacokinetic (PBPK) modeling to study the dose-dependent metabolism and excretion of verapamil and its preformed metabolite, norverapamil, to unravel the kinetics of norverapamil formation via N-demethylation. Various initial verapamil (1, 50, and 100 μM) and preformed norverapamil (1.5 and 5 μM) concentrations, perfused at 12 ml/min, were investigated in the...

The main purpose of this rat study was to investigate the effect of rifampicin on the effective permeability (P(eff)) of R/S-verapamil in the rat jejunum. In addition the effect on metabolism of R/S-verapamil to R/S-norverapamil was examined. In situ single-pass perfusions of the rat jejunum were performed in animals pretreated with oral rifampicin (250 mg/kg/day) or saline (control) over vario...

A bioequivalence study of two verapamil formulations (generic verapamil tablets and Isoptin(®) tablets) was performed by comparing pharmacokinetic parameters of the parent drug and its major metabolite, norverapamil following a single dose administration of 80 mg verapamil hydrochloride in 22 healthy volunteers according to a randomized, two-period, crossover-design study. Moreover, the feasibi...

To determine the effect of age on exposure to the circulating major verapamil metabolites norverapamil, N-dealkylverapamil (D-617), and N-dealkylnorverapamil (D-620), plasma concentrations of verapamil and the three metabolites were determined during the last dose interval of a 14-day administration period of 240 mg of sustained release verapamil once daily in 11 older (aged 65-75 years) and 8 ...

Verapamil inhibition of CYP3A activity results in many drug-drug interactions with CYP3A substrates, but the mechanism of inhibition is unclear. The present study showed that verapamil enantiomers and their major metabolites [norverapamil and N-desalkylverapamil (D617)] inhibited CYP3A in a time- and concentration-dependent manner by using pooled human liver microsomes and the cDNA-expressed CY...

A bioequivalence study of two verapamil formulations (generic verapamil tablets and Isoptin® tablets) was performed by comparing pharmacokinetic parameters of the parent drug and its major metabolite, norverapamil following a single dose administration of 80 mg verapamil hydrochloride in 22 healthy volunteers according to a randomized, two-period, crossover-design study. Moreover, the feasibili...

A bioequivalence study of two verapamil formulations (generic verapamil tablets and Isoptin® tablets) was performed by comparing pharmacokinetic parameters of the parent drug and its major metabolite, norverapamil following a single dose administration of 80 mg verapamil hydrochloride in 22 healthy volunteers according to a randomized, two-period, crossover-design study. Moreover, the feasibili...

a bioequivalence study of two verapamil formulations (generic verapamil tablets and isoptin® tablets) was performed by comparing pharmacokinetic parameters of the parent drug and its major metabolite, norverapamil following a single dose administration of 80 mg verapamil hydrochloride in 22 healthy volunteers according to a randomized, two-period, crossover-design study. moreover, the feasibili...

We present a procedure for the determination of verapamil and its metabolite, norverapamil, in serum. The drugs are extracted under basic conditions into n-heptane/2-butanol (96/4 by vol) and then extracted again into 1 mol/L H2SO4. The acidic solution is made basic with sodium hydroxide, re-extracted with diethyl ether, and the extract evaporated. The residue is redissolved in ethanol and anal...

Verapamil is subject to extensive oxidative metabolism mediated by cytochrome P450 enzymes with less than 5% of an oral dose being excreted unchanged in urine. Furthermore, verapamil is known to be a potent inhibitor of P-glycoprotein function. There is evidence from in vivo investigations that some verapamil metabolites might be actively transported. The aim of the present study was to investi...