The pharmacokinetics of oxybutynin is unaffected by gender and contraceptive steroids.
OBJECTIVE
The effect of gender and concomitant use of contraceptive steroids on the absorption and metabolism of oxybutynin was investigated in 49 healthy volunteers, 24 females and 25 males. Serum concentrations of oxybutynin and its active metabolite, N-desethyloxybutynin, were measured for up to 48 h after ingestion of a single dose of 10 mg oxybutynin.


RESULTS
Intake of oral contraceptive steroids had no significant effect on the pharmacokinetic parameters of oxybutynin or its metabolite. Both in males and females, the mean area under the curve (AUC0-t) of N-desethyloxybutynin was about 13 times higher and the peak concentration (Cmax) 15 to 19 times higher than the AUC0-t and Cmax of the parent oxybutynin, with no significant differences between males and females.


CONCLUSIONS
The pharmacokinetics of orally administered oxybutynin shows a considerable interindividual variability, but is unaffected by gender and use of contraceptive steroids.
Lukkari
E
E
Department of Clinical Pharmacology, University of Helsinki, Haartmaninkatu, Finland.
Hakonen
T
T
Neuvonen
P J
PJ
D000284:Administration, Oral; D000328:Adult; D019540:Area Under Curve; D018680:Cholinergic Antagonists / Q000378:metabolism / Q000493:pharmacokinetics*; D003278:Contraceptives, Oral, Hormonal / Q000494:pharmacology*; D004347:Drug Interactions; D005260:Female; D006801:Humans; D008297:Male; D008333:Mandelic Acids / Q000378:metabolism / Q000493:pharmacokinetics*; D012737:Sex Factors
D018680:Cholinergic Antagonists; D003278:Contraceptives, Oral, Hormonal; D008333:Mandelic Acids; C005419:oxybutynin