Adults

Typical dosage for GERD: 20 mg once daily for 4-8 weeks. For duodenal ulcer: 20 mg once daily for 2-4 weeks. For gastric ulcer: 20 mg once daily for 4-8 weeks. For H. pylori eradication: 20 mg twice daily in combination with antibiotics for 7-14 days. For Zollinger-Ellison syndrome: Initial 60 mg once daily, adjusted as needed. In patients with severe hepatic impairment, a daily dose of 10-20 mg may be sufficient and should be considered.

Elderly

No specific dose adjustment is generally required for elderly patients with normal renal and hepatic function, but caution is advised.

Renal_impairment

No dosage adjustment is necessary for patients with impaired renal function.

Onset

Within 1 hour

Excretion

Mainly excreted in urine (approx. 77%) as metabolites, and a smaller amount in feces (approx. 23%).

Half life

0.5-1 hour

Absorption

Rapidly absorbed from the gastrointestinal tract, primarily in the small intestine. Bioavailability is about 30-40% after a single oral dose, increasing to approximately 60% after repeated doses (due to reduced first-pass metabolism).

Metabolism

Extensively metabolized in the liver by the cytochrome P450 system (primarily CYP2C19 and CYP3A4) to inactive metabolites.

Warfarin

Increased INR/prothrombin time; monitor closely.

Nelfinavir

Decreased nelfinavir levels due to altered gastric pH; contraindicated.

Clopidogrel

Reduced antiplatelet effect of clopidogrel (due to inhibition of CYP2C19, which metabolizes clopidogrel to its active form).

Methotrexate

Increased methotrexate levels, particularly with high-dose methotrexate; monitor for toxicity.

Diazepam, Phenytoin, Citalopram

Increased plasma concentrations of these drugs due to inhibition of hepatic metabolism.