Unimed Omeprazole Drug Interactions

Due to the decreased intragastric acidity, the absorption of ketoconazole or itraconazole may be reduced during omeprazole therapy as it is during treatment with other acid secretion inhibitors. As omeprazole is metabolised in the liver through cytochrome it can prolong the elimination of diazepam, phenytoin and warfarin. Monitoring of patients receiving phenytoin or warfarin is recommended and a reduction of phenytoin or warfarin dose may be necessary when Omeprazole is added to treatment. However, concomitant treatment with Omeprazole 20 mg orally daily, did not change the blood concentration of phenytoin in patients on continuous treatment with phenytoin. Similarly, concomitant treatment with Omeprazole 20 mg orally daily, did not change coagulation time in patients on continuous treatment with warfarin.
Plasma concentrations of omeprazole and clarithromycin are increased during concomitant oral administration. There is no interaction with metronidazole or amoxicillin. These antimicrobials are used together with omeprazole for eradication of Helicobacter pylori.
There is no evidence of an interaction with phenacetin, theophylline, caffeine, propranolol, metoprolol, ciclosporin, lidocaine, quinidine, estradiol, or antacids when Omeprazole is given orally. The absorption of Omeprazole given orally is not affected by alcohol or food.
There is no evidence of an interaction with piroxicam, diclofenac or naproxen, this is considered useful when patients are required to continue these treatments.
Simultaneous treatment with omeprazole and digoxin in healthy subjects led to a 10% increase in the bioavailability of digoxin as a consequence of the increased intragastric pH.
Interaction with other drugs also metabolised via the cytochrome P450 system cannot be excluded. Co-administration of omeprazole (40mg once daily) with atazanavir 300 mg/ritonavir 100mg to healthy volunteers resulted in a substantial reduction in atazanavir exposure (approximately 75% decrease in AUC, Cmax, and Cmin). Increasing the atazanavir dose to 400mg did not compensate for the impact of omeprazole on atazanavir exposure. PPIs including omeprazole should not be co-administered with atazanavir.
Concomitant administration of omeprazole and tacrolimus may increase the serum levels of tacrolimus.