Journal of pharmaceutical and biomedical analysis
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J Pharm Biomed Anal · Aug 2002
A sensitive LC-MS/MS assay for the determination of dextromethorphan and metabolites in human urine--application for drug interaction studies assessing potential CYP3A and CYP2D6 inhibition.
The commonly used antitussive dextromethorphan can be used to simultaneously assess potential cytochrome P450 3A (CYP3A) and CYP2D6 inhibition during drug development. The metabolism of dextromethorphan to dextrorphan and subsequently to 3-hydroxymorphinan are via the 2D6 pathway, while the metabolism of dextromethorphan to 3-methoxymorphinan is via the 3A pathway. A sensitive and specific LC-MS/MS assay has been developed to determine the human urine concentrations of dextromethorphan and three metabolites (dextrorphan, 3-methoxymorphinan and 3-hydroxymorphinan) in support of drug interaction studies. ⋯ The stability of analytes in urine was demonstrated for 9 months at -20 degrees C, 24 h under ambient conditions and for up to three freeze/thaw cycles. The method described herein is suitable for the rapid and efficient measurement of dextromethorphan and different metabolites to estimate potential CYP3A inhibition by drug candidates and for screening of extensive and poor metabolizers of CYP2D6 in the heterogeneous population. The method has subsequently been validated on a Sciex API 3000 with lower limit of quantitation; 1.00 ng/ml for dextromethorphan and 3-methoxymorphinan; 60.0 ng/ml for dextrorphan and 100 ng/ml for 3-hydroxymorphinan.