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Information about Cimetidine

Cimetidine is a histamine type 2 receptor antagonist (H2 blocker) which is widely used for treatment of acid-peptic disease and heartburn. 

Liver safety of Cimetidine

Cimetidine has been linked to rare instances of clinically apparent acute liver injury.

Mechanism of action of Cimetidine

Cimetidine (sye met' i deen) was the first H2 blocker introduced into clinical practice in the United States and remains a commonly used agent for treatment of duodenal and gastric ulcer and gastroesophageal reflux disease.  The H2 blockers are specific antagonists of the histamine type 2 receptor, which is found on the basolateral (antiluminal) membrane of gastric parietal cells.  The binding of cimetidine to the H2 receptor results in inhibition of acid production and secretion, and improvement in symptoms and signs of acid-peptic disease.  The H2 blockers inhibit an early, “upstream” step in gastric acid production and are less potent that the proton pump inhibitors, which inhibit the final common step in acid secretion.  Nevertheless, the H2 blockers inhibit 24 hour gastric acid production by about 70% and are most effective in blocking basal and nocturnal acid production. 

FDA approval information for Cimetidine

Cimetidine was first approved for use in the United States in 1977 and is still used widely both by prescription and in over-the-counter forms.  The listed indications for cimetidine include duodenal and gastric ulcer disease, gastroesophageal reflux and prevention of stress ulcers. 

Dosage and administration for Cimetidine

Cimetidine is available by prescription in tablets of 200, 300, 400 and 800 mg in several generic forms and in both oral and parenteral forms under the brand name Tagamet.  Over-the-counter preparations are usually tablets of 200 mg.  The typical recommended dose of cimetidine for peptic ulcer disease in adults is 300 to 400 mg twice daily or 800 mg at night for up to 8 weeks, and maintenance doses of 400 mg once daily.  Lower chronic or intermittent doses are commonly used to treat heartburn and indigestion. 

Side effects of Cimetidine

Side effects are uncommon, usually minor, and include diarrhea, constipation, fatigue, drowsiness, headache and muscle aches.  Cimetidine is metabolized by and can inhibit several isoforms of the hepatic cytochrome P450 system (CYP 1A2, 2C9 and 2D6), which can result in significant drug-drug interactions if administered with agents that rely upon their metabolism by these microsomal enzymes (such as digoxin, warfarin, oral contraceptives, isoniazid and phenytoin).

The antiulcer agents in clinical use

Proton Pump Inhibitors

Selective Histamine Type 2 Receptor Antagonists or H2 Blockers

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