rac-Desethyl oxybutynin is an active metabolite of the muscarinic acetylcholine receptor (mAChR) antagonist oxybutynin .^1,2,3rac-Desethyl oxybutynin is formed from oxybutynin by the cytochrome P450 (CYP) isoform CYP3A4.²It binds to mAChRs in isolated rat bladder, submaxillary gland, heart, and colon with K_ivalues of 5.38, 3.12, 16, and 5.59 nM, respectively.rac-Desethyl oxybutynin (0.4 and 0.8 mg/kg) reduces micturition pressure in rats.³

1.Lindeke, B., HallstrÖm, G., Johansson, C., et al.Metabolism of Oxybutynin: Establishment of desethyloxybutynin and oxybutynin N-oxide formation in rat liver preparation using deuterium substitution and gas chromatographic mass spectrometric analysisBiomed. Mass Spectrom.8(10)506-513(1981) 2.Oki, T., Kawashima, A., Uchida, M., et al.In vivo demonstration of muscarinic receptor binding activity of N-desethyl-oxybutynin, active metabolite of oxybutyninLife Sci.76(21)2445-2456(2005) 3.Mizushima, H., Kinoshita, K., Abe, K., et al.Pharmacokinetics/pharmacodynamics analysis of the relationship between the in vivo micturition pressure and receptor occupancy of (R)-oxybutynin and its metabolite in ratsBiol. Pharm. Bull.30(5)955-962(2007)