title: The hydroxylation of omeprazole correlates with S-mephenytoin metabolism: a population study.
abstract: We compared omeprazole and mephenytoin as probes for the CYP2C19 metabolic polymorphism. Single oral doses of omeprazole (20 mg) or mephenytoin (100 mg) were administered at least 1 week apart to 167 healthy volunteers. Mephenytoin metabolism was measured using the amount of 4'-hydroxymephenytoin and the S/R ratio of mephenytoin in an 8-hour urine collection. Omeprazole hydroxylation was measured using the ratio of omeprazole to 5'-hydroxyomeprazole in serum 2 hours after dosing. All three methods separated poor- or extensive-metabolizer phenotypes with complete concordance. Omeprazole hydroxylation correlated with the S/R ratio of mephenytoin in extensive metabolizers (r2 = 0.681; p < 0.001). Genotyping tests showed that six poor metabolizers of omeprazole were homozygous for a single base pair mutation in exon 5 of CYP2C19. These results support the hypothesis that omeprazole 5'-hydroxylation cosegregates with the CYP2C19 metabolic polymorphism.
authors.affiliation: Department of Medicine and Pharmacology, Georgetown University Medical Center, Washington, DC 20007, USA.
authors.forename: J D
authors.initials: JD
authors.lastname: Balian
authors.forename: N
authors.initials: N
authors.lastname: Sukhova
authors.forename: J W
authors.initials: JW
authors.lastname: Harris
authors.forename: J
authors.initials: J
authors.lastname: Hewett
authors.forename: L
authors.initials: L
authors.lastname: Pickle
authors.forename: J A
authors.initials: JA
authors.lastname: Goldstein
authors.forename: R L
authors.initials: RL
authors.lastname: Woosley
authors.forename: D A
authors.initials: DA
authors.lastname: Flockhart
mesh_terms: D000328:Adult; D001189:Aryl Hydrocarbon Hydroxylases; D065731:Cytochrome P-450 CYP2C19; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D005260:Female; D005838:Genotype; D006801:Humans; D006900:Hydroxylation; D008297:Male; D008617:Mephenytoin / Q000493:pharmacokinetics*; D008875:Middle Aged; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism*; D009853:Omeprazole / Q000493:pharmacokinetics*; D010641:Phenotype; D016133:Polymerase Chain Reaction; D012016:Reference Values
chemical_list: D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C045793:CYP2C19 protein, human; D065731:Cytochrome P-450 CYP2C19; D009853:Omeprazole; D008617:Mephenytoin