Gas chromatographic-mass spectrometric analysis of plasma oxybutynin using a deuterated internal standard |
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Authors: | K S Patrick J S Markowitz E J Jarvi A B Straughn M C Meyer |
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Affiliation: | Department of Medicinal Chemistry, College of Pharmacy, University of Tennessee, Memphis 38163. |
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Abstract: | 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. |
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