Histamine H2-receptor antagonists, also called H2 blockers, are medications that help reduce the production of gastric acid.
Because of that, they can be used to treat peptic ulcers; gastroesophageal reflux disease, or GERD; and Zollinger-Ellison syndrome, which is a rare condition caused by gastrin-secreting tumors. In addition, histamine H2-receptor antagonists can be used to prevent stress-induced ulcers.
These medications include cimetidine, which can be administered orally, intravenously, and intramuscularly; famotidine, which is given orally or intravenously; and nizatidine, which is given orally.
Now, gastric acid is secreted by the parietal cells, which have different membrane receptors that modulate their activity. One of them is the H2 histamine receptor.
Normally, the stomach is protected from the acidic environment by the mucus secreted by foveolar cells, and the esophagus is protected by the lower esophageal sphincter, which prevents gastric acid from coming back up.
When some of these mechanisms fail, the person can develop peptic ulcers or gastroesophageal reflux disease.
Histamine H2-receptor antagonists block H2 receptors so histamine can’t bind them, which decreases gastric acid secretion, and in turn mitigates the harmful effects of gastric acid in these disorders.
Generally, histamine H2-receptor antagonists are safe medications. However, they may cause some side effects, since H2 receptors are not only located in the stomach.