Risek/Risek Insta Drug Interactions

Risek: Commonly with the use of other inhibitors of acid secretion or antacids, the absorption of ketoconazole and itraconazole can be decreased due to decreased intragastric acidity during treatment with omeprazole.
Omeprazole inhibits CYP2C19. Thus, when omeprazole is combined with drugs metabolized by CYP2C19 eg, diazepam, citalopram, imipramine, clomipramine, phenytoin, etc, the plasma concentrations of these drugs may be increased and a dose reduction could be needed.
Risek Insta: Omeprazole can prolong the elimination of diazepam, warfarin and phenytoin, drugs that are metabolized by oxidation in the liver.
There have been reports of increased international normalized ratio (INR) and prothrombin time in patients receiving proton-pump inhibitors eg, omeprazole and warfarin concomitantly. Increase in INR and prothrombin time may lead to abnormal bleeding and even death. Patients treated with proton-pump inhibitors and warfarin may need to be monitored for increase in INR and prothrombin time.
Although in normal subjects, no interaction with theophylline or propranolol was found, there have been clinical reports of interaction with other drugs metabolized via the cytochrome P-450 system (eg, cyclosporine, disulfiram, benzodiazepines). Patients should be monitored to determine if it is necessary to adjust the dosage of these drugs when taken concomitantly with omeprazole.
Because of its profound and long-lasting inhibition of gastric acid secretion, it is theoretically possible that omeprazole may interfere with absorption of drugs where gastric pH is an important determinant of their bioavailability (eg, ketoconazole, ampicillin esters and iron salts).
Concomitant administration of omeprazole and atazanavir has been reported to reduce the plasma levels of atazanavir.
Concomitant administration of omeprazole and tacrolimus may increase the serum levels of tacrolimus.
Co-administration of omeprazole and clarithromycin have resulted in increase of plasma levels of omeprazole, clarithromycin and 14-hydroxyclarithromycin.