Omeprazole is a first-generation proton pump inhibitor (PPI) that provides potent and long-lasting inhibition of gastric acid secretion. It is a substituted benzimidazole prodrug that irreversibly blocks the H+/K+ ATPase enzyme system (the proton pump) at the secretory surface of the gastric parietal cell. It is a mainstay of therapy for acid-peptic disorders in the Indian population, valued for its efficacy, safety, and wide availability across multiple price points.
Adult: GERD/Erosive Esophagitis: 20-40 mg once daily for 4-8 weeks. Maintenance: 20 mg once daily. Duodenal Ulcer: 20 mg once daily for 4-8 weeks. H. pylori Eradication (Triple Therapy): Omeprazole 20 mg + Amoxicillin 1000 mg + Clarithromycin 500 mg, all twice daily for 10-14 days. Hypersecretory Conditions: Starting dose 60 mg once daily; adjust based on acid output (up to 120 mg three times daily).
Note: Take on an empty stomach, at least 1 hour before a meal, preferably in the morning. Swallow the capsule/tablet whole with a glass of water; do not crush, chew, or break. For patients with swallowing difficulties, some formulations (e.g., MUPS tablets) can be dispersed in water. Do not take with antacids simultaneously; if needed, take antacids at least 2 hours apart.
Omeprazole is a prodrug. It is a weak base that accumulates in the acidic secretory canaliculi of the parietal cell. In this acidic environment, it is protonated and rearranges into its active form, a cyclic sulfenamide. This active metabolite forms covalent disulfide bonds with cysteine residues (specifically Cys813 and Cys892) on the alpha subunit of the H+/K+ ATPase enzyme (the proton pump), irreversibly inhibiting it. This blocks the final step of gastric acid secretion, leading to profound and long-lasting suppression of both basal and stimulated acid production.
Pregnancy: Pregnancy Category C (US FDA). Animal studies have shown evidence of fetotoxicity at high doses. Use during pregnancy only if the potential benefit justifies the potential risk to the fetus. Considered a treatment option for severe GERD in pregnancy after lifestyle modifications and antacids fail.
Driving: Omeprazole may rarely cause dizziness and visual disturbances. Patients experiencing these effects should not drive or operate machinery.
| Clopidogrel | Omeprazole (a CYP2C19 inhibitor) may reduce the antiplatelet effect of clopidogrel (a prodrug activated by CYP2C19), potentially increasing cardiovascular risk. | Major |
| Diazepam, Phenytoin, Warfarin | Omeprazole may inhibit their metabolism (via CYP2C19), increasing their plasma levels and risk of toxicity. Monitor and adjust dose. | Moderate |
| Ketoconazole, Itraconazole, Atazanavir | Omeprazole increases gastric pH, reducing the absorption of these drugs, leading to decreased efficacy. | Moderate |
| Methotrexate | Omeprazole may reduce renal clearance of methotrexate, increasing its toxicity, especially with high-dose methotrexate. | Major |
| Rifampicin, St. John's Wort | These CYP inducers may increase omeprazole metabolism, reducing its efficacy. | Moderate |
| Cilostazol | Omeprazole may increase cilostazol levels (active metabolite). Dose reduction of cilostazol may be needed. | Moderate |
| Digoxin | Increased gastric pH may slightly increase digoxin bioavailability. | Minor |