Cimetidine
Cimetidine is an H2 receptor antagonist that reduces stomach acid production by blocking histamine signals in the stomach, treating peptic ulcers, GERD, and related conditions.
Cimetidine is an acid-reducing medication used to treat ulcers and heartburn by blocking stomach acid production.
Key facts at a glance
- ATC
- A02BA01
- RxNorm
- 2541
- Generic
- Cimetidine
- Class
- atc-a02
- Brands
- Tagamet
- Availability
- rx
- Lactation
- unknown
- Routes
- oral
- Forms
- tablet, suspension, solution
- Regions
- US, EU, CN, JP
- Monitoring
- —
This page is for informational purposes only.
Do not use this information to diagnose yourself or to replace a physician's advice. Always consult a qualified healthcare provider before starting, stopping, or changing any medication. If you believe you are experiencing a medical emergency, call your local emergency number immediately.
Cimetidine treats gastric and duodenal ulcers, gastroesophageal reflux disease (GERD), heartburn, and conditions involving excessive stomach acid secretion such as Zollinger-Ellison syndrome. It may also be used to prevent ulcer recurrence and manage indigestion.
Cimetidine works by blocking H2 (histamine-2) receptors on stomach cells called parietal cells, which are responsible for acid secretion. By inhibiting this pathway, it reduces the amount of acid produced in the stomach, allowing ulcers to heal and relieving acid-related symptoms.
Cimetidine can interact with numerous medications by inhibiting liver enzymes (cytochrome P450), potentially altering their effects. It may cause side effects such as headache, dizziness, diarrhea, and in rare cases, anti-androgenic effects. Patients should inform their healthcare provider of all medications and medical conditions before use.
Official drug label
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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 25, 2026. · Read our editorial policy