%0 Journal Article %A R K Lynn %A J E Bauer %A W P Gordon %A R G Smith %A D Griffin %A R M Thompson %A R Jenkins %A N Gerber %T Characterization of mephenytoin metabolites in human urine by gas chromatography and mass spectrometry. %D 1979 %J Drug Metabolism and Disposition %P 138-144 %V 7 %N 3 %X Metabolites of mephenytoin (5-ethyl-3-methyl-5-phenylhydantoin) were characterized in human urine following chromatography on XAD-2 resin, permethylation, and combined gas chromatography and mass spectrometry. Four glucuronide metabolites previously unidentified in man were characterized as their permethylated derivatives by chemical-ionization and electron-impact mass spectrometry. These metabolites included 5-ethyl-5-(hydroxyphenyl)-3-methylhydantoin O-glucuronide; 5-hydroxyethyl-3-methyl-5-phenyl-hydantoin O-glucuronide; 5-ethyl-5-(hydroxymethoxyphenyl)-3-methylhydantoin O-glucuronide; and a metabolite tentatively identified as 5-ethyl-5-phenylhydantoin N3-glucuronide in which both N-demethylation and glucuronide conjugation of the hydantoin ring have occurred. Mephenytoin, N-demethylmephenytoin, 5-ethyl-5-(hydroxyphenyl)-3-methylhydantoin, and 5-ethyl-5-(hydroxymethoxyphenyl)-3-methylhydantoin were characterized in extracts of enzymatically hydrolyzed urine. %U https://dmd.aspetjournals.org/content/dmd/7/3/138.full.pdf