Omeprazole

Proton pump inhibitor (PPI), Gastric acid suppressant

Omeprazole

Prilosec, Losec, Zegerid

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Summary

Classes

Proton pump inhibitor (PPI), Gastric acid suppressant

Pharmacy

Starting dose

20 mg PO once daily 30-60 minutes before breakfast

Preparations

10, 20, 40 mg delayed-release capsules and tablets; 2 mg/mL oral suspension; immediate-release combo with sodium bicarbonate (Zegerid)

US FDA Max

40 mg/d typical; up to 360 mg/d for Zollinger-Ellison

Pharmacology

Routes

Oral, IV

Onset

Symptom relief 1-4 days; full acid suppression after 3-5 days of dosing

Duration

24-72 hours per dose (irreversible enzyme binding; effect outlasts plasma exposure)

Half-life

0.5-1.5 hours (plasma); pharmacodynamic effect persists 24+ hours

Bioavailability

30-40% (oral; increases with repeated dosing as gastric pH rises)

Pregnancy

Widely used in pregnancy; meta-analyses do not show increased malformation risk.^{[citation needed]}

Legal status

OTC (20 mg) and Rx-only (higher doses) in US

Purported mechanism

Omeprazole is a prodrug activated in the acidic environment of parietal-cell secretory canaliculi to a sulfenamide that covalently binds the H+/K+ ATPase, irreversibly blocking the final common step of gastric acid secretion.▲0▼ Recovery of acid output requires synthesis of new pump enzyme. CYP2C19 substrate; PGx genotype substantially affects exposure and efficacy.