Zomep Drug Interactions

Omeprazole and other proton pump inhibitors are metabolized by the cytochrome P450 system, primarily by isoenzyme CYP2C19, and to smaller extent by CY3A4. Inhibitors or inducers of these isoenzymes may affect exposure to Omeprazole and other proton pump inhibitors. In turn, proton pump inhibitors may alter the metabolism of some drugs metabolized by these enzymes. Omeprazole may prolong the elimination of diazepam, phenytoin and warfarin. Omeprazole and other proton pump inhibitors can reduce the absorption of drugs such as dasatinib, ketoconazole and itraconazole, whose absorption is dependent on an acid gastric pH. With voriconazole, the plasma concentration of both drugs maybe increased. Other proton pump inhibitors may be similarly affected by voriconazole. Omeprazole and other proton pump inhibitors should not be used with atazanavir, as it substantially reduces exposure to atazanavir. Omeprazole is metabolized primarily by the cytochrome P450 isoenzyme YP2C19 and therefor may interact with Diazepam. Some metabolism of phenytoin, tolbutamide, and the R-enantiomer of warfarin also takes place by CYP2C19, but the effect seen have been minor. Although some induction of CYP1 A2, which metabolizes caffeine and theophylline, has been reported this does not appear to be clinically significant. While some consider the effect of Omeprazole on CYP3A4 activity to be insignificant, others have noted an increasing body of evidence that competitive inhibition of intestinal CYP3A4 by Omeprazole may affect the first ­pass metabolism of a number of drugs. A review concluded that, while Omeprazole and possibly Esomeprazole have a considerable potential for drug interactions, Lansoprazole, Pantoprazole and Rabeprazole are associated with a lower incidence of drug interactions.
Clarithromycin: Clarithromycin inhibits the metabolism of Omeprazole mediated by the cytochrome P450 isoenzyme CYP3A4. The interaction may contribute to the benefits of combined therapy for Helicobacter pylori infection.
Fluvoxamine: Omeprazole and other proton pump inhibitors are metabolized mainly by cytochrome P450 isoenzyme CYP2C19, which shows genetically determined polymorphism, yielding extensive metabolizers and poor metabolizers.
Fluvoxamine increased exposure to omeprazole, lanzoprazole and rabeprazole in patients who are extensive metabolizers, but had no effect on pharmacokinetic parameters in poor metabolizers. Dose reductions may need to be considered in patients treated with fluvoxamine and proton pump inhibitors.