Types of medicine
What Is an H2 Blocker? Acid-Reducing Medicines Explained
Histamine-2 receptor antagonist · say it: HIS-tuh-meen TOO ree-SEP-ter an-TAG-uh-nistAlso written: H2 blocker, H2 receptor antagonist, H2RA, H2 antagonist, famotidine
Short answer
An H2 blocker (histamine-2 receptor antagonist) is a type of medicine that reduces stomach acid by blocking histamine in the stomach lining.
What it means
Histamine-2 receptor antagonists, usually called H2 blockers, are medicines that lower the amount of acid the stomach makes. Histamine is a natural chemical that, among other jobs, tells acid-making cells in the stomach to produce acid. H2 blockers block the H2 receptors on those cells. Famotidine is an example; generic names usually end in '-tidine'.
They appear on over-the-counter and prescription labels for heartburn, acid indigestion, GERD and stomach or duodenal ulcers. Labels say to ask a doctor if heartburn lasts a long time or if you have trouble swallowing, vomiting with blood or unexplained weight loss, as these need checking. Some labels also mention dose changes for people with kidney problems.
H2 blockers are different from antihistamines used for allergies, which block H1 receptors. They are also different from proton pump inhibitors (PPIs), which reduce acid more strongly by a different route, and from antacids, which neutralise acid that is already there.
Where you may see it
- The 'Uses' and 'Directions' sections of over-the-counter acid reducer labels
- Prescription labels for ulcer and GERD treatment
- Pharmacy medication lists
📄 How it looks on a report
Uses: prevents heartburn associated with acid indigestion brought on by eating certain foods and drinks.
🙅 What it does not mean
- An H2 blocker is not the same as an allergy antihistamine, even though both block histamine.
- It does not work instantly like an antacid; it lowers acid production over time.
- Needing it often is a reason to see a doctor, not to keep increasing the dose yourself.
🗒️ Questions to ask your doctor
💊 Medicines whose labels mention “Histamine-2 receptor antagonist”
Plain-English explanations of each medicine, from its official FDA label.
- Aripiprazole
an atypical antipsychotic medicine
- Famotidine
A histamine-2 (H2) receptor blocker, a type of medicine that lowers stomach acid.
🔗 Read more from trusted sources
- “Histamine-2 receptor antagonist” on MedlinePlus ↗
US National Library of Medicine
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