[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Proton pump inhibitors (PPIs)](https://durgical.com/en/pharmacology/classes/proton-pump-inhibitors/) › Omeprazole [Pharmacology](https://durgical.com/en/pharmacology/) · [Proton pump inhibitors (PPIs)](https://durgical.com/en/pharmacology/classes/proton-pump-inhibitors/) # Omeprazole Switches off the stomach acid pump long after it leaves the blood; used for reflux, ulcers, ulcer bleeding and, with antibiotics, to clear H. pylori. Updated 2026-11-01 - Class: [Proton pump inhibitors (PPIs)](https://durgical.com/en/pharmacology/classes/proton-pump-inhibitors/) - Transporter: Gastric H⁺/K⁺-ATPase (proton pump), α subunit - ATC code: A02BC01 - WHO Model List of Essential Medicines ⇄**Gastric H⁺/K⁺-ATPase (proton pump), α subunit**Omeprazole ⓘ The crystal is the pig gastric pump bound to vonoprazan, a reversible acid blocker; the figure highlights Cys813, the cysteine to which activated omeprazole bonds covalently. **Target in 3D:** Gastric H⁺/K⁺-ATPase (proton pump), α subunit. PDB structure 5YLU (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/5YLU) · Drag to rotate · pinch to zoom ## Mechanism of action Omeprazole is a prodrug and a weak base. It accumulates in the acidic secretory canaliculus of the parietal cell, where acid turns it into a reactive sulfenamide. This forms a disulfide bond with Cys813 on the luminal side of the H⁺/K⁺-ATPase and locks the pump, so it can no longer exchange K⁺ for H⁺. Acid output falls until new pumps are made. - Collects in the acidic canaliculus of the parietal cell - Acid converts it into a reactive sulfenamide - A disulfide bond to Cys813 locks the H⁺/K⁺ pump - Less acid: the oesophagus and ulcers heal ## Pharmacokinetics **Absorption** Acid-sensitive, so it comes in delayed-release (enteric-coated) forms that release it in the small intestine. **Distribution** About 95% bound to plasma proteins. **Metabolism** Liver, mainly by CYP2C19 (to hydroxyomeprazole) and partly CYP3A4 (to omeprazole sulfone). **Elimination** Most of a dose leaves in the urine as inactive metabolites. **Half-life** About half an hour to an hour, but the effect lasts much longer because the pumps are blocked irreversibly. **Onset and duration** Acid output falls within about an hour of a dose; the effect builds up with repeated daily use. ## Indications - Gastro-oesophageal reflux disease and erosive oesophagitis. [Gastro-oesophageal reflux disease (GERD) →](https://durgical.com/en/conditions/gastro-oesophageal-reflux-disease/) - Gastric and duodenal ulcers. [Peptic ulcer disease →](https://durgical.com/en/conditions/peptic-ulcer-disease/) - H. pylori eradication, combined with amoxicillin and clarithromycin. [Helicobacter pylori gastritis →](https://durgical.com/en/conditions/helicobacter-pylori-gastritis/) - Gastrointestinal bleeding from peptic ulcer (listed for this use on the WHO Essential Medicines List). [Upper gastrointestinal bleeding →](https://durgical.com/en/conditions/upper-gastrointestinal-bleeding/) - Zollinger–Ellison syndrome and other states of acid hypersecretion. ## Adverse effects ### Common - Headache - Abdominal pain, nausea and diarrhoea - Flatulence ### Serious (rare, important) - Vitamin B12 deficiency with long-term use - Low magnesium with prolonged use - Clostridioides difficile diarrhoea, especially in hospital - Hip, wrist and spine fractures with long-term use - Acute interstitial nephritis; fundic gland polyps with long-term use ## Contraindications - Hypersensitivity to omeprazole or other benzimidazole PPIs - Use with rilpivirine, which needs gastric acid to be absorbed ## Key interactions **Clopidogrel** Omeprazole reduces clopidogrel's active metabolite and its platelet inhibition; the combination is avoided. **Methotrexate (mainly high doses)** Methotrexate levels may rise. **Drugs that need acid to be absorbed (iron salts, ketoconazole, itraconazole)** Lower absorption and effect. **Diazepam, phenytoin and warfarin** More sedation with diazepam; phenytoin levels and INR are checked. ## What is monitored - Magnesium and vitamin B12 with long-term use - Periodic review of whether treatment is still needed ## Memory aid Omeprazole is a sleeping key that only wakes up in acid; once awake it welds itself to Cys813 and the pump stays locked until the cell builds a new one. ## Test yourself Think of the answer, then tap the question to see it. ## Why must omeprazole reach acid to work, and where does that happen? It is a prodrug; acid converts it into the reactive sulfenamide. This happens in the secretory canaliculus of the parietal cell, right next to the pump. ## Which amino acid of the H⁺/K⁺-ATPase does activated omeprazole bond to, and what kind of bond is it? Cysteine 813, through a covalent disulfide bond, which inactivates the pump irreversibly. ## A patient on clopidogrel after a coronary stent is started on omeprazole. What is the concern? Omeprazole inhibits CYP2C19, which turns clopidogrel into its active form, so platelet inhibition may be weaker. ## Why can long-term omeprazole lead to vitamin B12 deficiency? Gastric acid and pepsin free B12 from food proteins; with little acid, less B12 is released for absorption. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/pharmacology/omeprazole/) ## Related drugs - [Amoxicillin](https://durgical.com/en/pharmacology/amoxicillin/) ## Related conditions - [Gastro-oesophageal reflux disease (GERD)](https://durgical.com/en/conditions/gastro-oesophageal-reflux-disease/) - [Peptic ulcer disease](https://durgical.com/en/conditions/peptic-ulcer-disease/) - [Helicobacter pylori gastritis](https://durgical.com/en/conditions/helicobacter-pylori-gastritis/) - [Upper gastrointestinal bleeding](https://durgical.com/en/conditions/upper-gastrointestinal-bleeding/) [← Back to the class: Proton pump inhibitors (PPIs)](https://durgical.com/en/pharmacology/classes/proton-pump-inhibitors/) Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given. Sources: [Omeprazole: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a693050.html) (MedlinePlus (U.S. National Library of Medicine), 2023); [DailyMed - OMEPRAZOLE capsule, delayed release](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=934601b6-fbba-43c4-a8ef-7a7dfe9f9a51) (DailyMed (U.S. National Library of Medicine), 2024); [RCSB PDB - 5YLU: Crystal structure of the gastric proton pump complexed with vonoprazan](https://www.rcsb.org/structure/5YLU) (RCSB Protein Data Bank, 2026); [eEML - Electronic Essential Medicines List](https://list.essentialmeds.org/) (World Health Organization, 2025). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/pharmacology/omeprazole/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/omeprazole/