ISSN:
1432-1041
Keywords:
carvedilol
;
enantiomer pharmacokinetics
;
bioavailability
;
first-pass effect
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Medicine
Notes:
Summary The racemic compound carvedilol is a multiple-action oral antihypertensive drug that exhibits both vasodilator and non-selective beta-adrenergic blocking activities. The effects of the levorotatoryS-enantiomer [S( − )-CARV] are vasodilatation and beta-blockade. TheR (+)-enantiomer [R (+)-CARV] is a pure vasodilating agent. Quantitative determination of the enantiomers in human plasma by HPLC was carried out after formation of diastereoisomers with the chiral reagent 2,3,4,6-tetraO-acetyl-β-d-glucopyranosyl isothiocyanate (GITC). The pharmacokinetics of the enantiomers were studied following i. v. (12.5 mg in 1 h) and p. o. (50 mg) administration of racemic carvedilol in ten healthy male subjects according to a randomized crossover design. The AUCs ofS (−)-CARV were significantly lower than those ofR (+)-CARV after both i. v. and p. o. administration. The systemic clearance of the two enantiomers was significantly different, whereas half-lives and apparent distribution volumes were comparable. Following p. o. administration, the absolute bioavailability (31.1% and 15.1%, respectively) and maximal plasma concentrations ofR (+ )-CARV were twice those ofS (−)-CARV A similar difference was found in the half-lives. A close correlation existed between enantiomeric ratios after i.v. and after p. o. administration, demonstrating slight intraindividual variability. The preferential systemic clearance of theS ( − )-enantiomer suggests stereoselective hepatic metabolism of carvedilol, becoming especially apparent after p. o. administration. The small intrasubject variability in enantiomer ratios indicates a relatively constant relation of beta-blockade to vasodilation during chronic treatment.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01409476
