title: Simultaneous determination of p-hydroxylated and dihydrodiol metabolites of phenytoin in urine by high-performance liquid chromatography.
abstract: Accurate urinary measurements of the two major metabolites of phenytoin, 5-(p-hydroxyphenyl)-5-phenylhydantoin (p-HPPH) and 5-(3,4-dihydroxy-cyclohexa-1,5-dienyl)-5-phenylhydantoin (dihydrodiol, DHD), are necessary for pharmacokinetic and drug-interaction studies of this commonly used antiepileptic drug. We describe a simple, rapid, acid hydrolysis, with liquid-liquid extraction and simultaneous isocratic reversed-phase high-performance liquid chromatography of p-HPPH and 5-(m-hydroxyphenyl)-5-phenylhydantoin (m-HPPH) (hydrolytic end product of DHD). p-HPPH and m-HPPH were quantitated against their separate respective internal standards of alphenal and tolylbarb. The mobile phase consisted of water-dioxane-tetrahydrofuran (80:15:5, v/v/v) at 2 ml/min and at 50 degrees C, with detection at 225 nm. Baseline separation was achieved by use of a 16 cm x 3.9 mm Nova-Pak C18 column and total analysis time of 12 min. p-HPPH and m-HPPH concentrations ranged from 10 to 200 and from 2 to 30 micrograms/ml, respectively, with between-day coefficients of variations of 3.3-4.5% and 2.2-5.1% for controls. All standard curves were linear with r values greater than 0.993. The DHD concentration was determined by multiplying m-HPPH concentrations by 2.3.
authors.affiliation: Neuropharmacology Laboratory, Boston University School of Medicine MA.
authors.forename: G K
authors.initials: GK
authors.lastname: Szabo
authors.forename: R J
authors.initials: RJ
authors.lastname: Pylilo
authors.forename: H
authors.initials: H
authors.lastname: Davoudi
authors.forename: T R
authors.initials: TR
authors.lastname: Browne
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D006801:Humans; D006900:Hydroxylation; D010672:Phenytoin / Q000378:metabolism / Q000652:urine*
chemical_list: D010672:Phenytoin