H2blockerare

H2blockerare is a class of medicines that reduce gastric acid production by competitively blocking histamine H2 receptors on parietal cells in the stomach. By inhibiting these receptors, they decrease the intracellular signaling that stimulates acid secretion, leading to lower basal and meal-stimulated acid output. They are used to treat conditions related to excess stomach acid, such as peptic ulcers, gastroesophageal reflux disease (GERD), dyspepsia, and erosive esophagitis, and can be employed for short-term symptom relief or healing therapy.

Mechanism of action and pharmacology: H2blockerare are reversible antagonists of the histamine H2 receptor. Their effect reduces cAMP production in parietal cells, resulting in decreased acid secretion. They have a slower onset of action than some acid-suppressing drugs but provide relatively sustained suppression of acid production, particularly with nightly dosing. Dosing often requires adjustment for kidney function.

Common agents: The best known members are famotidine, ranitidine, cimetidine, and nizatidine. Ranitidine has been withdrawn from many markets due to concerns about nitrosamine contamination in some formulations, while famotidine remains widely used. Cimetidine is associated with more drug interactions and antiandrogenic effects, making it less favored in some settings. Nizatidine is less commonly used today.

Indications and use: H2blockerare are employed for short- and intermediate-term management of ulcers and GERD, relief of dyspeptic symptoms, and maintenance therapy to prevent relapse. They are usually prescribed for use over days to weeks, with longer-term use evaluated against alternative therapies, such as proton pump inhibitors.

Safety and side effects: Most people tolerate them well. Common adverse effects include headache, dizziness, constipation or diarrhea. Rare but notable risks include confusion in the elderly, gynecomastia and galactorrhea with cimetidine, and drug interactions due to cytochrome P450 inhibition. Long-term acid suppression may be associated with infection risk and nutrient malabsorption in some patients.

History: H2blockerare were introduced in the 1970s as the first targeted gastric acid–suppressing therapy. They have largely been superseded for many indications by proton pump inhibitors but remain useful for specific cases and shorter courses.