Increased omeprazole metabolism in carriers of the CYP2C19*17 allele;: a pharmacokinetic study in healthy volunteers

AIMS To investigate the influence of the CYP2C19*17 allele on the pharmacokinetics of omeprazole, a commonly used CYP2C19 probe drug, in healthy volunteers. METHODS In a single-dose pharmacokinetic study, 17 healthy White volunteers genotyped as either CYP2C19*17/*17 or CYP2C19*1/*1 received an oral dose of 40 mg of omeprazole. Plasma was sampled for up to 10 h postdose, followed by quantification of omeprazole, 5-hydroxy omeprazole and omeprazole sulphone by high-performance liquid chromatography. RESULTS The mean omeprazole AUC(infinity) of 1973 h nmol l(-1) in CYP2C19*17/*17 subjects was 2.1-fold lower [95% confidence interval (CI) 1.1, 3.3] than in CYP2C19*1/*1 subjects (4151 h nmol l(-1), P = 0.04). A similar trend was observed for the sulphone metabolite with the CYP2C19*17/*17 group having a mean AUC(infinity) of 1083 h nmol l(-1), 3.1-fold lower (95% CI 1.2, 5.5) than the CYP2C19*1/*1 group (3343 h nmol l(-1), P = 0.03). A pronounced correlation (r(2) = 0.95, P < 0.0001) was seen in the intraindividual omeprazole AUC(infinity) and omeprazole sulphone AUC(infinity) values. CONCLUSIONS The pharmacokinetics of omeprazole and omeprazole sulphone differ significantly between homozygous CYP2C19*17 and CYP2C19*1 subjects. For clinically important drugs that are metabolized predominantly by CYP2C19, the CYP2C19*17 allele might be associated with subtherapeutic drug exposure.