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  • enantiomers  (2)
  • enantioselectivity  (1)
  • probenecid  (1)
  • 1
    ISSN: 1573-904X
    Keywords: enantioselectivity ; pharmacokinetics ; oxprenolol ; oxprenolol glucuronides ; probenecid ; active renal secretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To study the effect of probenecid on the stereoselective pharmacokinetics of oxprenolol and its glucuronides in the rabbit. Methods. An oral dose of 50 mg/kg racemic oxprenolol was given to nine rabbits twice, in random sequence with and without the concurrent administration of probenecid. Oxprenolol enantiomers were determined in plasma and urine by an enantioselective HPLC method. Oxprenolol glucuronides were measured in plasma and urine after enzymatic hydrolysis. Results. The disposition of the oxprenolol enantiomers in rabbits is stereoselective, mainly due to a difference in metabolism. Renal excretion is only a minor elimination route for unchanged oxprenolol, and the renal clearances of the enantiomers are similar. Pre-treatment with probenecid did not affect the plasma concentrations of the oxprenolol enantiomers, but there was a slight decrease in their urinary excretion. The plasma concentrations of the oxprenolol glucuronides are much higher than those of the parent enantiomers, and those of (S)-glucuronide are about twice those of its antipode. About 10% of the oxprenolol dose is excreted in the urine as glucuronides. The renal clearances of both glucuronides are similar, and markedly higher than the creatinine clearance. After probenecid, the mean glucuronide plasma levels were markedly higher, with for both glucuronides a more than twofold increase in mean AUC. Probenecid decreased the renal clearance of both glucuronides to about 30%. Moreover, it decreased slightly the formation clearance of (S)-glucuronide, while the formation clearance of (R)-glucuronide was not significantly influenced. Conclusions. Our results show that in the rabbit, both oxprenolol glucuronide diastereomers are actively secreted by the kidney, and that this process is inhibited by probenecid.
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  • 2
    ISSN: 0899-0042
    Keywords: oxprenolol ; propranolol ; verapamil ; enantiomers ; inflammation ; endotoxin ; protein binding ; pharmacokinetics ; species ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of endotoxin-induced inflammation was studied on the pharmacokinetics of the enantiomers of the racemic drugs oxprenolol, propranolol, and verapamil in rabbits and dogs. Enantioselective pharmacokinetics were seen for oxprenolol and propranolol in the rabbit and for propranolol and verapamil in the dog. In the dog, the enantioselective differences in plasma concentrations are due to differences in both protein binding and metabolism, whereas in the rabbit the differences are due solely to differences in metabolism. In both species endotoxin treatment increases the plasma concentrations of the enantiomers of the three drugs; both protein binding and metabolism are influenced. In rabbits and in dogs, the influence of endotoxin on the disposition of the three drugs is less enantioselective than was previously observed in the rat. © 1995 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
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  • 3
    ISSN: 0899-0042
    Keywords: β-adrenergic blocking agent ; calcium antagonist ; enantiomers ; inflammation ; protein binding ; pharmacokinetics ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of endotoxin-induced inflammation on the enantioselective pharmacokinetics of propranolol, oxprenolol, and verapamil, which bind to α1-acid glycoprotein, was studied in the rat. The racemic mixtures were given orally. In the control animals, for propranolol and oxprenolol, the plasma concentrations of the (R)-enantiomer were higher than those of the (S)-enantiomer, while for verapamil the reverse was true. Protein binding and intrinsic clearance are the main factors responsible for this enantioselectivity. After endotoxin treatment, for the three drugs tested the plasma concentrations and the plasma binding of both enantiomers were significantly increased. This effect was more pronounced for (R)-propranolol, (R)-oxprenolol, and (S)-verapamil than for their respective antipodes. The enantioselective effect of endotoxin on the plasma concentrations of the drugs studied seems mainly due to the enantioselective increase in binding to α1-acid glycoprotein. © 1994 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
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