Omeprazole
Omeprazole
Prilosec, Losec, Zegerid
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Summary
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[2]
Bioavailability
30-40% (oral; increases with repeated dosing as gastric pH rises)[2]
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[1].
References
- ↑ CPIC Guideline for CYP2C19 and Proton Pump Inhibitors, 2020. https://cpicpgx.org/guidelines/cpic-guideline-for-proton-pump-inhibitors-and-cyp2c19/
- ↑ 2.0 2.1 FDA Prescribing Information, Prilosec (omeprazole), AstraZeneca, current revision. https://www.accessdata.fda.gov/drugsatfda_docs/label/2012/019810s096lbl.pdf