Cimetidiini

Cimetidiini, also known as histamine H2-receptor antagonists, are a class of drugs that reduce gastric acid secretion. The class includes cimetidine and related agents such as ranitidine, famotidine, and nizatidine. They act by competitively inhibiting histamine H2 receptors on gastric parietal cells, decreasing both basal and meal-stimulated gastric acid production, which raises gastric pH and provides symptom relief in acid-related disorders.

Indications include peptic ulcer disease, gastritis, gastroesophageal reflux disease, and prevention of stress ulcers in hospitalized patients. They are also used for dyspepsia and to reduce acid injury in NSAID-associated ulcers; sometimes used before endoscopy.

Pharmacokinetics and administration: available orally and by injection; onset of action within 30-60 minutes; half-life a couple of hours; metabolism in the liver; excretion via the kidneys; long-term use requires monitoring of renal function.

Safety: generally well tolerated; common adverse effects include headache, dizziness, and constipation or diarrhea. Cimetidine in particular has been associated with antiandrogenic effects (galactorrhea, gynecomastia, impotence) and numerous drug interactions due to inhibition of cytochrome P450 enzymes (CYP1A2, 2C9, 2D6, 3A4). Other cimetidiini have fewer interactions. Caution in elderly and in patients with renal impairment; rare hepatic toxicity; pneumonia risk; and potential for rebound acid hypersecretion after abrupt discontinuation.

History: these agents were among the first to revolutionize the management of peptic ulcer disease after their introduction in the 1970s. While use has declined with the rise of proton pump inhibitors, cimetidiini remain available in many regions for acid-related conditions.