How Do Histamine H2 Antagonists Work?

Histamine H2 receptor antagonists (H2RAs) or H2-blockers are a class of stomach acid-suppressing agents and are used to treat gastroesophageal reflux and duodenal ulcers. H2RAs suppress the release of stomach acid to treat conditions caused by excess acid secretion. The stomach wall consists of acid-secreting cells (parietal cells), which have histamine receptors (H2) on them. Usually, after a meal, the stomach secretes a hormone (gastrin), which stimulates histamine release from cells called enterochromaffin-like cells. The released histamine binds to the H2 receptors located on parietal cells to release stomach acid.

H2RAs compete with histamine to bind to the H2 receptor, thereby inhibiting the binding and action of histamine. By blocking the action of histamine, H2RAs prevent the release of stomach acid from the parietal cells.

As H2RAs suppress the release of stomach acid, they are mainly used to treat:

• Mild gastroesophageal reflux disease
• Gastric or duodenal ulcers
• Heartburn
• Indigestion
• Hypersecretory conditions

H2RAs, when administered orally, can cause the following side effects:

• Headache
• Dizziness
• Confusion
• Diarrhea
• Nausea
• Vomiting
• Drowsiness
• Gynecomastia (swollen male breast tissue)
• Impotence
• Insomnia
• Itching
• Anxiety
• Abdominal pain

The information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with other medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.

Generic and brand names of H2RA drugs include:

• Acid controller
• Act
• Axid
• Cimetidine
• Dyspep HB
• Famotidine
• Fluxid
• Nizatidine
• Pepcid
• Ranitidine
• Tagamet HB
• Zantac
• Zantac 150 maximum strength
• Zantac 75