Omeprazole drug interactions

List of drug interactions
Diazepam/warfarin/phenytoin Drugs metabolized via the cytochrome P-450 system Ketoconazole/ampicillin esters/iron salts Atazanavir Tacrolimus Clarithromycin

Diazepam/warfarin/phenytoin
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 INR and prothrombin time in patients receiving proton pump inhibitors, including Omeprazole, and warfarin concomitantly. Increases 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 increases in INR and prothrombin time. Return to top

Drugs metabolized via the cytochrome P-450 system
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 (e.g., 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. Return to top

Ketoconazole/ampicillin esters/iron salts
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 (e.g., ketoconazole, ampicillin esters, and iron salts). In the clinical trials, antacids were used concomitantly with the administration of Omeprazole. Return to top

Atazanavir
Concomitant administration of Omeprazole has been reported to reduce the plasma levels of atazanavir, thus appropriate clinical monitoring is recommended. Return to top

Tacrolimus
Concomitant administration of Omeprazole and tacrolimus may increase the serum levels of tacrolimus. Return to top

Clarithromycin
Co-administration of Omeprazole and clarithromycin have resulted in increases in plasma levels of Omeprazole, clarithromycin, and 14-hydroxy-clarithromycin. Concomitant administration of clarithromycin with cisapride, pimozide, or terfenadine is contraindicated. There have been reports of an interaction between erythromycin and astemizole resulting in QT prolongation and torsades de pointes. Concomitant administration of erythromycin and astemizole is contraindicated. Because clarithromycin is also metabolized by cytochrome P-450, concomitant administration of clarithromycin with astemizole is not recommended. Return to top