Omeprazole does not enhance the metabolism of phenacetin a marker of cyp1a2 activity in healthy volunteers

S. Xiaodong, G. Gatti, A. Bartoli, G. Cipolla, F. Crema, E. Perucca

Research output: Contribution to journalArticlepeer-review


Omeprazole has been reported to increase cytochrome P450IA2 (CYP1A2) activity in vitro, but whether this effect also occurs in vivo is controversial. To clarify this issue, the effect of omeprazole (20 mg/day for 8 days) on the kinetics and metabolism of phenacetin, an in vivo marker of CYP1A2 activity, was examined in 10 healthy volunteers. The pharmacokinetic parameters of phenacetin and metabolically derived paracetamol on the 8th day of omeprazole administration were very similar to those observed in a control session in the absence of omeprazole administration, the only significant difference being a higher peak plasma phenacetin concentration during omeprazole treatment. It is concluded that at the dosage used omeprazole does not increase the rate of oxidative and conjugative reactions involved in the metabolism of phenacetin and paracetamol respectively. These data are consistent with the hypothesis that omeprazole is generally devoid of inducing effects on CYP1A2 activity in vivo, at least in a Caucasian population with a low prevalence of the omeprazole-mephenytoin poor metabolizer phenotype.

Original languageEnglish
Pages (from-to)248-250
Number of pages3
JournalTherapeutic Drug Monitoring
Issue number3
Publication statusPublished - 1994


  • CYP1A2
  • Enzyme induction
  • Omeprazole
  • Paracetamol
  • Phenacetin

ASJC Scopus subject areas

  • Pharmacology (medical)
  • Pharmacology
  • Toxicology
  • Health, Toxicology and Mutagenesis
  • Biochemistry
  • Biochemistry, Genetics and Molecular Biology(all)
  • Public Health, Environmental and Occupational Health


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