Diazepam, Warfarin and Phenytoin: Since Omeprazole is metabolised in the liver via cytochrome P-450 2C19 (CYP2C19) enzyme system in the liver; therefore, it prolongs their elimination. Monitoring of patients also receiving Warfarin or Phenytoin is recommended and reduction of dose of Phenytoin and Warfarin may be necessary.
Propranolol, Theophylline: No interaction has been found out.
Antacids: No interactions have been found out when concomitantly administered.
Avoid concomitant use of clopidogrel and omeprazole. Coadministration of clopidogrel with 80 mg omeprazole, a proton pump inhibitor that is an inhibitor of CYP2C19, reduces the pharmacological activity of clopidogrel if given concomitantly or if given 12 hours apart.
Decreased gastric acidity due to any means, including proton pump inhibitors, increases gastric counts of bacteria normally present in the gastrointestinal tract. Treatment with proton pump inhibitors may lead to slightly increased risk of gastrointestinal infections such as Salmonella and Campylobacter and possibly Clostridium difficile.
Concomitant use of Proton Pump Inhibitors (PPIs) with Methotrexate: Literature suggests that concomitant use of PPIs with methotrexate (primarily at high dose) may elevate and prolong serum levels of methotrexate and/or its metabolite, possibly leading to methotrexate toxicities. A temporary withdrawal of the PPI may be considered in some patients receiving treatments with high dose methotrexate.
Case reports, published population pharmacokinetic studies, and retrospective analyses suggest that concomitant administration of PPIs and methotrexate (primarily at high dose) may elevate and prolong serum levels of methotrexate and/or its metabolite hydroxymethotrexate. However, no formal drug interaction studies of methotrexate with PPIs have been conducted.