Gas chromatographic-mass spectrometric analysis of plasma oxybutynin using a deuterated internal standard
Patrick, K.S.; Markowitz, J.S.; Jarvi, E.J.; Straughn, A.B.; Meyer, M.C.
Journal of Chromatography 487(1): 91-98
1989
ISSN/ISBN: 0021-9673 PMID: 2715278 Document Number: 341488
A gas chromatographic-mass spectrometric method is described for the quantitative analysis of plasma oxybutynin. Deuterated oxybutynin served as the internal standard and its synthesis is described. Chromatographic separation on a methylsilicone capillary column avoided the thermal decomposition observed using a packed column. Electron-impact ionization and selected-ion monitoring of the .alpha.-cleavage fragments of drug and internal standard permitted quantitation of oxybutynin down to 0.25 ng/ml of plasma. At the 2 ng/ml level the accuracy and precision are 4 and 10%, respectively, and improved at higher drug concentrations. Application of the method to the pharmacokinetics of oral oxybutynin in man demonstrated rapid absorption and elimination of the drug.