The hydroxylation of omeprazole correlates with S-mephenytoin metabolism: A population study

John D. Balian, Nadia Sukhova, James W. Harris, Jan Hewett, Linda Pickle, Joyce A. Goldstein, Raymond L. Woosley, David A. Flockhart

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173 Scopus citations


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 SIR 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 SIR 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.

Original languageEnglish (US)
Pages (from-to)662-669
Number of pages8
JournalClinical pharmacology and therapeutics
Issue number6
StatePublished - 1995

All Science Journal Classification (ASJC) codes

  • Pharmacology
  • Pharmacology (medical)


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