Products
H2 receptor antagonists were commercially available in many countries in tablet, effervescent tablet, and solution for injection forms, among others. Currently, no more drugs are available. Due to proton pump inhibitors (PPI), H2 antagonists have become less important. The first active ingredient, cimetidine (Tagamet), was developed in the 1960s and 70s under the leadership of Sir James Black and became commercially available in the 1970s. Cimetidine quickly became a blockbuster.
Structure and properties
The H2 receptor antagonists are usually low-molecular-weight and nitrogen-containing compounds that contain heterocycles (e.g., imidazole, thiazole). They are organic cations that have similarities to the natural ligand histamine and have also been developed as histamine analogs.
Effects
H2 receptor antagonists (ATC A02BA) inhibit basal and stimulated secretion of gastric acid and pepsin. The effects are due to antagonism at the histamine H2 receptor. The effect generally occurs after about one hour.
Indications
Possible indications include:
- Stomach burning, acidity of the stomach.
- Acid regurgitation (gastroesophageal reflux), reflux esophagitis.
- Gastric and intestinal ulcers
- Zollinger-Ellison syndrome
- Helicobacter pylori eradication (combination therapy).
- Stomach protection
Dosage
According to the professional information. The tablets are usually taken one to three times a day. Administration depends on the active ingredient.
Active ingredients
The drugs are not currently marketed in many countries:
- Ranitidine (Zantic, generic, off-label).
- Cimetidine (Tagamet, generic, over-the-counter).
- Famotidine (Pepcid)
- Nizatidine (Tazac, Axid)
- Roxatidine
- Lafutidin
Contraindications
Contraindications include (selection):
- Hypersensitivity, including to other H2 receptor antagonists.
- Children and adolescents (eg, cimetidine).
For complete precautions, see the drug label.
Interactions
H2 receptor antagonists are organic cations that are subject to renal secretion. There, they may compete competitively with other organic cations. Other interactions are possible because of the elevation of gastric pH. Cimetidine is an inhibitor of several CYP450 isozymes.
Adverse effects
The most common possible adverse effects include digestive upset, headache, and dizziness.
