Patrick KS, Markowitz JS, Jarvi EJ, Straughn AB, Meyer MC. Gas chromatographic-mass spectrometric analysis of plasma oxybutynin using a deuterated internal standard.
JOURNAL OF CHROMATOGRAPHY 1989;
487:91-8. [PMID:
2715278 DOI:
10.1016/s0378-4347(00)83010-8]
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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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