Histamine 2 antagonists
Histamine 2 antagonists, commonly referred to as H2 blockers or acid blockers, are medications designed to reduce stomach acid production by blocking histamine from binding to the H2 receptors in the stomach lining. These drugs are particularly useful for treating conditions such as gastroesophageal reflux disease (GERD), multiple endocrine neoplasia (MEN), Zollinger-Ellison syndrome, and Barrett's esophagus, a precancerous condition linked to chronic acid exposure. They can be administered via various routes, including intravenously and orally in forms such as tablets or liquids.
H2 antagonists work by decreasing the secretion of hydrochloric acid, which is crucial for digestion, thereby alleviating symptoms associated with excess stomach acid. While generally safe, these medications may cause side effects, such as mild diarrhea, allergic reactions, and potential gastrointestinal absorption issues. In rare cases, intravenous use may lead to irregular heartbeat or elevated blood pressure. Additionally, some research suggests that H2 blockers may play a role in reducing tumor growth in certain colorectal cancer cell lines, although the underlying mechanisms are not yet fully understood.
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Histamine 2 antagonists
ATC CODE: A02BA
DEFINITION: Histamine 2 antagonists block acid production in the stomach.
Cancers treated:Multiple endocrine neoplasia (MEN), Zollinger-Ellison syndrome, Barrett's esophagus (BE)
Delivery routes: These drugs are administered intravenously or orally as tablets, capsules, chewable tablets, or liquids.
How these drugs work: Fluids in the stomach, composed primarily of hydrochloric acid and enzymes that break down proteins, aid in the digestion of food. Hydrochloric acid secretion can be triggered when histamine binds to one of its receptors, the H2 receptor, in the cells lining the stomach (parietal cells). If the lower esophageal sphincter (the muscle between the stomach and the esophagus) is not working correctly, stomach acids may flow into the esophagus, causing heartburn and esophageal cell damage. Prolonged exposure to stomach acid in the esophagus can lead to gastroesophageal reflux disease (GERD) or acid reflux disease.
Histamine 2 antagonists (H2RAs), also known as acid blockers or H2 blockers, are competitive and reversible inhibitors of histamine. They block histamine's ability to bind to the H2 receptor and, therefore, decrease stomach acid production, reduce the risk of acid reflux, and help prevent ulcers in the stomach and small intestine.
H2RAs may treat multiple endocrine neoplasia (MEN) and Zollinger-Ellison syndrome, where digestive tract tumors stimulate excess stomach acid production. Barrett's esophagus (BE) is a precancerous condition in which normal cells lining the esophagus are damaged due to GERD and replaced with abnormal or cancerous cells. It may also be treated with H2RAs. Additionally, H2RAs may be administered before chemotherapy to help manage gastrointestinal side effects.
Side effects: Common side effects of H2RAs include mild diarrhea, allergic reactions, flu-like symptoms, and bruising or bleeding easily. Intravenous (IV) administration of H2RAs has been associated with rare cases of irregular heartbeat and elevated blood pressure. H2RAs may also reduce the body’s ability to absorb drugs that require an acidic stomach environment.
Some studies have shown that histamine can also promote the growth of certain colorectal cancer cell lines, with H2RAs abrogating these effects and inducing tumor cell death. The mechanism behind these observations has yet to be fully understood.
Bibliography
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