"H2 Blockers" is the common name for histamine type 2 (H2) receptor antagonists. These medications relieve conditions such as ulcers and heartburn by decreasing stomach acid secretion. H2 blockers are available in both over the counter and prescription forms; for example, Pepcid® (famotidine), Tagamet® (cimetidine), Zantac® (ranitidine), and Axid® (nizatidine) are all over-the-counter H2 Blockers which are available by prescription at higher doses.
In their over-the-counter form, H2 Blockers are normally used for the treatment of heartburn and other discomforts caused by excess stomach acid. In prescription-strength form, H-2 Blockers are often used to treat and prevent the recurrence of gastric or duodenal ulcers. Although most ulcers can only be cured by eliminating the H. pylori bacteria which cause the condition, H2 blockers can help some ulcers heal more rapidly and prevent their return. H2 Blockers are also used to treat gastroesophageal reflux disease.
H2 Blockers act by preventing the stomach lining’s parietal cells from secreting acid. The stomach normally produces acid when histamine, a chemical messenger, reaches an H2 receptor in a particular cell in the stomach lining. H2 Blockers "block" the histamine from the receptor, preventing the cell from secreting acid into the stomach. In contrast, antacids work to neutralize the acid already produced.
H2 Blockers can interfere with skin tests for allergies, and they have not been studied on humans during pregnancy. However, side effects are unusual for this medication, except among elderly patients. When they do occur, they may include mild diarrhea, constipation, dry skin, rash, runny nose, headache, and dizziness.
Last updated: 25-Jun-03