What it does
Omeprazole is a medication that reduces stomach acid. It helps relieve symptoms associated with acid-related conditions.
Commonly used for: stomach ulcers, gastroesophageal reflux disease (GERD), excessive stomach acid
Read more in plain English ↓Plain-language summary for general understanding - not medical advice. Always follow your pharmacist/doctor.
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Sourcing - Kenya onlyRegistration & product details
Source: Food and Drugs Authority · fetched 2026-04-18 08:33:03 · updated 2026-09-18 04:00:04
Drug Interactions
4Moderate (2)
Omeprazole - increases exposure
Cenobamate moderately increases the exposure to proton pump inhibitors (omeprazole). Adjust dose.
Omeprazole - increases exposure
Fedratinib moderately increases the exposure to proton pump inhibitors (omeprazole). Monitor and adjust dose.
Unknown (2)
Cilostazol - increases exposure
Omeprazole is predicted to increase the exposure to cilostazol. Adjust cilostazol dose, p. 253.
Omeprazole - decreases exposure
Apalutamide markedly decreases the exposure to proton pump inhibitors (omeprazole). Avoid or monitor.
Data from BNF 85 (British National Formulary). This is not a substitute for professional medical advice. Matched via: exact
About this medicine
Omeprazole is a medication that reduces stomach acid. It helps relieve symptoms associated with acid-related conditions.
What it treats
- stomach ulcers
- gastroesophageal reflux disease (GERD)
- excessive stomach acid
How it works
Omeprazole works by blocking the production of stomach acid, which helps heal ulcers and reduce heartburn.
Who it's for
Omeprazole is for adults and children over a certain age who have problems with too much stomach acid.
AI-assisted summary grounded in BNF data - general information only, not medical advice. Always confirm with your pharmacist or doctor.
Clinical monograph: Omeprazole
BNF-referencedOmeprazole is a proton pump inhibitor (PPI) that reduces gastric acid secretion by inhibiting the H+/K+ ATPase enzyme system at the secretory surface of the gastric parietal cells. It is primarily used for the treatment of conditions associated with excessive gastric acid production, such as peptic ulcers and gastro-oesophageal reflux disease (GERD).
Indications
- Gastric ulcer
- Duodenal ulcer
- Gastro-oesophageal reflux disease (GERD)
- Severe oesophagitis
- Helicobacter pylori eradication (in combination therapy)
- Prevention of NSAID-associated gastric and duodenal ulcers
- Zollinger-Ellison syndrome
Dosage
Adults: The usual dose for adults is 20 mg once daily for 4 weeks for duodenal ulcer and GERD. For gastric ulcer, the dose may be 20 mg to 40 mg once daily
Mechanism of action
Omeprazole works by specifically binding to the proton pump (H+/K+ ATPase) in the gastric parietal cells, leading to irreversible inhibition of acid secretion. This binding prevents the exchange of hydrogen ions for potassium ions, effectively reducing the production of gastric acid and promoting healing of acid-related conditions.
Pharmacodynamics
The pharmacodynamic effects of omeprazole manifest as a significant decrease in gastric acidity, which improves symptoms related to excessive acid secretion. The onset of action typically occurs within an hour of administration, with maximum effect seen within 2 to 4 days of continuous use. The duration of action allows for once-daily dosing in most indications.
Pharmacokinetics
Omeprazole is rapidly absorbed from the gastrointestinal tract, reaching peak plasma concentrations within 0.5 to 3.5 hours after oral administration. It is extensively metabolized in the liver via the cytochrome P450 system, primarily CYP2C19 and CYP3A4, leading to the formation of inactive metabolites. The elimination half-life is approximately 0.5 to 1 hour, but the effects on gastric acid secretion last much longer due to the irreversible nature of proton pump inhibition. Omeprazole is excreted mainly in the urine as metabolites, with less than 1% of the drug excreted unchanged.
Contra-indications
- Hypersensitivity to omeprazole or any component of the formulation
- Use with caution in patients with severe liver impairment
Adverse effects
- Nausea
- Vomiting
- Diarrhea
- Headache
- Abdominal pain
- Flatulence
- Constipation
- Dizziness
- Fatigue
- Rash
- Muscle weakness
- Gastrointestinal candidiasis
- Aggression
- Agitation
- Bronchospasm
- Encephalopathy
Interactions
- Cenobamate may increase exposure to omeprazole
- Fedratinib may increase exposure to omeprazole
- Apalutamide may decrease exposure to omeprazole
- Cilostazol may increase exposure to omeprazole
Precautions
- Monitor patients for gastrointestinal symptoms
- Use caution in patients with a history of liver disease
- Consider potential for vitamin B12 deficiency with long-term use
- Monitor for signs of Clostridium difficile infection in the colon
Pregnancy
Not known to be harmful during pregnancy, but should be used only if clearly needed.
Breast-feeding
Excreted in breast milk, caution is advised when administered to nursing mothers.
Storage
Store below 25 degrees Celsius. Protect from moisture. Keep out of reach of children.
Formulations
- Orodispersible tablets
- Gastro-resistant capsules
- Intravenous injection
- Oral suspension
AI-synthesized from BNF references - general information only, not a substitute for professional medical advice or the current BNF. Verify doses with a pharmacist.
Molecular reference: Omeprazole
PubChem CID 4594Molecular formula: C17H19N3O3S
Biological pathways
Source: PubChem (NCBI) · pathways from PathBank, Reactome, WikiPathways & PharmGKB.
This drug in other countries
The same active ingredient registered across other registries we cover - including different brands.