title: Metabolism of Oxybutynin: establishment of desethyloxybutynin and oxybutynin N-oxide formation in rat liver preparation using deuterium substitution and gas chromatographic mass spectrometric analysis.
abstract: Oxybutynin is rapidly metabolized in rat liver microsomes. Two major primary oxidation products were identified as N-desethyl oxybutynin and oxybutynin N-oxide. Deuterium substituted substrate was used to aid the identification. N-Desethyl oxybutynin was characterized by gas chromatography electron impact mass spectrometry as its trifluoroacetamide derivative and oxybutynin N-oxide was indicated by the presence of a decomposition product, 2-oxo-3-butenyl-2 cyclohexyl-2-phenylglycolate, as elucidated from the gas chromatographic mas spectrometric analysis. The formation of this product from synthetic oxybutynin N-oxide was verified and occurs by two consecutive rearrangements upon thermolysis of the unstable N-oxide. Attempted titanous chloride reduction of oxybutynin N-oxide resulted in the formation of the hydrolytic products 2-cyclohexyl-2-phenylglycolic acid and 4-diethylamino-2-butynol.
mesh_terms: D000818:Animals; D055598:Chemical Phenomena; D002621:Chemistry; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D008297:Male; D008333:Mandelic Acids / Q000302:isolation & purification* / Q000378:metabolism*; D008862:Microsomes, Liver / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D008333:Mandelic Acids; C032680:oxybutynin N-oxide; C032681:desethyloxybutynin; C005419:oxybutynin