Adults

Duodenal ulcer: 20 mg once daily for 2-4 weeks. Gastric ulcer: 20 mg once daily for 4-8 weeks. GERD: 20 mg once daily for 4-8 weeks, can be increased to 40 mg in severe cases. Zollinger-Ellison syndrome: Initial 60 mg once daily, adjusted as needed.

Elderly

No general dose adjustment is needed, but caution should be exercised and monitor for adverse effects.

Renal_impairment

No dose adjustment is required in patients with impaired renal function.

Onset

Onset of action within 0.5-3.5 hours.

Excretion

Approximately 77% of the dose is excreted as metabolites in the urine, and about 20% in the feces.

Half life

Plasma elimination half-life is approximately 0.5-1 hour.

Absorption

Rapidly absorbed from the small intestine after oral administration. Bioavailability is approximately 30-40% but increases to about 60% with repeated dosing due to reduced first-pass metabolism.

Metabolism

Extensively metabolized in the liver primarily by cytochrome P450 enzymes, mainly CYP2C19 and CYP3A4, to inactive metabolites.

Warfarin

Increased INR (International Normalized Ratio) and prothrombin time, increasing the risk of bleeding. Close monitoring is recommended.

Clopidogrel

Omeprazole may reduce the antiplatelet effect of clopidogrel by inhibiting CYP2C19, which converts clopidogrel to its active metabolite. Concomitant use is generally discouraged.

Methotrexate

Increased and prolonged elevation of serum methotrexate levels and/or its metabolite, possibly leading to methotrexate toxicity. Consider temporary PPI withdrawal.