title: Stereoselective determination of the CYP2C19 probe drug mephenytoin in human urine by gas chromatography-mass spectrometry.
abstract: A sensitive, specific and reproducible gas chromatographic assay utilizing mass-selective detection has been developed for the stereoselective determination of mephenytoin (MP) in human urine. Following extraction of urine samples using methyl tert.-butyl ether, separation of R- and S-MP was achieved with a chiral capillary column; detection and quantitation were accomplished by mass spectrometry in the single ion monitoring mode (m/z 104 and 189). Excellent linearity was observed for both enantiomers over the concentration range of 5-1000 ng/ml with corresponding correlation coefficients (r)>0.99. The intra- and inter-day precision and accuracy were within +/-5%. This method employs a simplified processing procedure, demonstrates improved extraction recovery, and provides at least 5-fold greater sensitivity than previously reported assays. This method is well suited for the phenotypic evaluation of CYP2C19 activity using mephenytoin.
authors.affiliation: Pharmacodynamic Research Center, Center for Pharmacogenetics, Department of Pharmaceutical Sciences, University of Pittsburgh, 15261, Pittsburgh, PA, USA.
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Nolin
authors.forename: Reginald F
authors.initials: RF
authors.lastname: Frye
mesh_terms: D000927:Anticonvulsants / Q000652:urine*; D001189:Aryl Hydrocarbon Hydroxylases / Q000378:metabolism*; D002138:Calibration; D065731:Cytochrome P-450 CYP2C19; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D006801:Humans; D008617:Mephenytoin / Q000652:urine*; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D010641:Phenotype; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D000927:Anticonvulsants; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C045793:CYP2C19 protein, human; D065731:Cytochrome P-450 CYP2C19; D008617:Mephenytoin