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Nonlinear kinetics after high-dose omeprazole caused by saturation of genetically variable CYP2C19
1Institute of Clinical Pharmacology, Universitätsklinikum Benjamin Franklin, Berlin, Germany.
Hepatology (Baltimore, Md.)
|June 1, 1996
Summary
High-dose omeprazole saturates the CYP2C19 pathway in extensive metabolizers, shifting metabolism to CYP3A. This can increase omeprazole concentrations and potential side effects, especially with CYP3A inhibitors.
Area of Science:
- Pharmacology
- Drug Metabolism
- Clinical Pharmacokinetics
Background:
- Omeprazole is metabolized by cytochrome P450 enzymes, primarily CYP2C19 and CYP3A.
- Individual variability in CYP2C19 activity affects omeprazole pharmacokinetics.
- High-dose omeprazole may lead to non-linear kinetics and altered metabolic profiles.
Purpose of the Study:
- To investigate the nonlinear kinetics of omeprazole and its metabolites under repeated high-dose treatment.
- To compare omeprazole metabolism in extensive metabolizers (EMs) and poor metabolizers (PMs) of CYP2C19.
- To elucidate the role of CYP2C19 and CYP3A in omeprazole elimination at high doses.
Main Methods:
- Repeated high-dose omeprazole administration (40 mg/d or 60 mg twice daily) for one week.
- Plasma pharmacokinetic analysis of omeprazole and its metabolites in EMs and PMs.
- Comparison of omeprazole kinetics between different doses and metabolizer phenotypes.
Main Results:
- CYP2C19 plays a dominant role in omeprazole metabolism at lower doses.
- High-dose omeprazole (60 mg BID) saturated CYP2C19 pathways in EMs, reducing plasma clearance.
- CYP3A became the predominant elimination route for omeprazole at high doses, with unaffected CYP3A-dependent routes.
Conclusions:
- High-dose omeprazole treatment reveals saturation kinetics for CYP2C19 pathways in EMs.
- CYP3A is the predominant enzyme for omeprazole elimination at high doses.
- Patients on high-dose omeprazole may face increased risk of side effects if co-administered with CYP3A inhibitors.