Absorption of medicinal products that are pH-dependent may decrease or increase depending on the reduced gastric acidity during treatment. Decreased plasma levels of atazanavir & nelfinavir. Increased digoxin bioavailability. Decreased mean exposure to the active metabolite of clopidogrel & mean reduction in max inhibition of platelet aggregation w/ clopidogrel. Significant reduction in absorption of posaconazole, erlotinib, ketoconazole & itraconazole. Reduced metabolism of other drugs metabolized by CYP2C19 enzyme [eg, diazepam, phenytoin, warfarin (R-warfarin) & other vit K antagonists & cilostazol]. Increased C
max & AUC of cilostazol. Monitor phenytoin plasma conc during the 1st 2 wk after initiating omeprazole treatment. Increased plasma levels of saquinavir & tacrolimus. Reports of increased MTX levels when co-administered w/ PPIs. Increased serum levels w/ CYP2C19 &/or CYP3A4 inhibitors (eg, clarithromycin & voriconazole). Decreased serum levels w/ CYP2C19 &/or CYP3A4 inducers (eg, rifampicin).