[Omeprazole and the cytochrome P450 system of the liver]

Enzymes of the cytochrome P450 family play a key role in xenobiotic and thus drug metabolism. The H+,K(+)-ATPase blocker, omeprazole, has been reported to inhibit (subfamily P450IIC) or induce (P450IA) this system. The slower metabolic elimination of diazepam, warfarin und phenytoin is probably due to omeprazole competition for P450IIC; however, this effect was rather negligible in magnitude and not reproducible in each case. Also induction of P450IA was only minor; it resulted in no (theophylline) or trivial changes (caffeine) in elimination of drugs metabolized by this subfamily. Concerns about a possible increase in activation of procarcinogens by P450IA appear illfounded, given the fact that cruciferous vegetables such as broccoli and Brussels sprouts are potent inducers but may rather be associated with a lower incidence of certain types of cancer.