Omeprazole

Omeprazole is a medication used to reduce the amount of acid produced in the stomach. Omeprazole is used for Gastroesophageal Reflux Disease (GERD), Peptic Ulcer Disease and Erosive Esophagitis.

Also called: Prilosec (United States) · Mezzopram (United Kingdom) · Olex (Canada) · Acimax (Australia) · Omezol (New Zealand)

Pronunciation: oh-MEP-rah-zole.

Last medically reviewed: September 28, 2026, by Dr. Roshan Basnet, MBBS, MD (Internal Medicine).

Generic name: Omeprazole
Brand names: Omee, Losec, Olex, Prilosec, UlcerGard, Acimax
Drug class: Proton Pump Inhibitor (PPI)

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What Omeprazole is and how it works

Omeprazole is a medication used to reduce the amount of acid produced in the stomach. It is commonly prescribed for conditions such as gastroesophageal reflux disease (GERD), peptic ulcer disease, erosive esophagitis, and Zollinger-Ellison syndrome. Omeprazole works by blocking the proton pumps in the stomach lining, which are responsible for secreting gastric acid. By decreasing acid production, it helps relieve symptoms like heartburn, allows ulcers to heal, and prevents damage to the esophagus caused by acid. Key points for patients: Omeprazole is usually taken once daily before a meal. It may take a few days to feel the full effect. Do not stop taking it suddenly without consulting your healthcare provider, and always follow the prescribed dose. (2) (3) (4)

Uses, formulations, monitoring, and supply rules can differ by patient, product, and country. Follow the exact local product information and professional advice.

Mechanism of action: how Omeprazole works

Omeprazole is a selective and irreversible proton pump inhibitor. It inhibits the H+/K+-ATPase enzyme system (proton pump) in the gastric parietal cells, leading to suppression of gastric acid secretion. This effect is dose-dependent and results in both basal and stimulated acid reduction. (1)

What is Omeprazole used for?

Gastroesophageal Reflux Disease (GERD)

Gastroesophageal Reflux Disease (GERD) (2) (3) (4)

Peptic Ulcer Disease

Peptic Ulcer Disease (2) (3) (4)

Erosive Esophagitis

Erosive Esophagitis (2) (3) (4)

Zollinger-Ellison Syndrome

Zollinger-Ellison Syndrome (2) (3) (4)

Prevention of NSAID-induced ulcers

Prevention of NSAID-induced ulcers (2) (3) (4)

Before taking Omeprazole

Do not take / not appropriate for

hypersensitivity to substituted benzimidazoles or to any component of the formulation. (Contraindication) (2)
concomitant use with rilpivirine-containing products. (Contraindication) (2)
when used in H. pylori combination therapy, also refer to clarithromycin and amoxicillin labeling for their own contraindications. (Contraindication) (2)

Tell your clinician about

(2) (3) (4)

Omeprazole dosage and how to take it

General Instructions: Take omeprazole exactly as prescribed, usually once daily before a meal. Swallow capsules or tablets whole; do not crush or chew.. Adult Dosing: Typical adult dose for GERD or ulcers: 20 mg to 40 mg once daily for 4-8 weeks. Dose may vary based on condition.. Pediatric Dosing: Dosing in children is based on weight and indication. For children over 1 year and ≥10 kg: 10 mg once daily, may increase as directed by a healthcare provider.. Administration: Take before meals, preferably in the morning. For oral suspension, mix with water as directed and take immediately.. When To Seek Review: Do not stop omeprazole suddenly without consulting your doctor, especially if used for long-term conditions. If a severe allergic reaction or serious side effect occurs, seek emergency medical attention; do not resume omeprazole without medical assessment.. Storage: Store at room temperature, away from moisture and heat. Keep out of reach of children.
This page does not provide a dose calculator. Dosing must follow the prescriber, pharmacist, or product label.

(2) (3) (4)

Procedures and treatment changes

Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (2) (3) (4)

Missed dose

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, contact your prescriber or pharmacist for guidance on the missed dose. Do not take two doses at the same time.

Overdose

Symptoms of overdose may include confusion, drowsiness, blurred vision, rapid heartbeat, nausea, and vomiting. Seek emergency medical attention or contact a poison control center immediately. (2) (3) (4)

Omeprazole side effects

Side effects and their urgency vary; report severe, persistent, or concerning symptoms to a healthcare professional.