Methotrexate: Case reports, published population pharmacokinetic studies, and retrospective analyses suggest that concomitant administration of PPIs and methotrexate (primarily at high dose; see methotrexate prescribing information) 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 (see Precautions).
Omeprazole can delay the elimination of diazepam, phenytoin and warfarin. Monitoring of patients receiving warfarin or phenytoin is recommended and a reduction of warfarin or phenytoin dose may be necessary when Omeprazole is added to treatment. There is no evidence of an interaction with theophylline, propranolol, metoprolol, lidocaine, quinidine, amoxicillin or antacids.
The absorption of Omeprazole is not affected by alcohol or food.