The metabolites, metabolizing organs of oxybutynin and its effect on the induction of drug metabolizing enzymes were investigated in rat, dog and human after oral administrations of oxybutynin and following the results were obtained.
1. Eight metabolites of oxybutynin and their glucuronide were identified in the dog and human urine after oral administration.
2. About 18 %, and 8.7 to 27.5 % of the administrated dose were excreted as a metabolites to urine in dogs and humans, respectively.
3. It was presumed that oxybutynin was metabolized by the following four pathways; a) de-ethylation b) hydrolysis of ester c) hydroxylation at 3' and 4' positions on cyclohexyl ring and d) conjugation of each metabolites.
4. The highest metabolic activity for oxybutynin was shown in the rat liver.
5. The induction of drug metabolizing enzymes by oxybutynin, administered orally every day for 8 days, was not found.
