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ALIMENTARY TRACT AND METABOLISM › DRUGS FOR ACID RELATED DISORDERS › DRUGS FOR PEPTIC ULCER AND GASTRO-OESOPHAGEAL REFLUX DISEASE (GORD) › H2-receptor antagonists
cimetidine, combinations
A02BA51
Forms & Strengths
- Oral tablet: 200 mg, 300 mg, 400 mg, 800 mg
- Oral solution: 300 mg/5 mL
- Intravenous/Intramuscular injection: 150 mg/mL
- Combination products with antacids (e.g., cimetidine/magnesium hydroxide/aluminum hydroxide)
Adult Dosing
- Duodenal ulcer (active): 300 mg qid with meals and at bedtime, or 800 mg qhs for up to 8 weeks
- Gastric ulcer (active): 300 mg qid with meals and at bedtime for 8 weeks
- GERD: 300 to 400 mg qid with meals and at bedtime for up to 12 weeks
- Pathological hypersecretory conditions: 300 mg qid; may increase up to 2400 mg/day in divided doses
- Max recommended daily dose: 2400 mg
Pediatric Dosing
- Neonates (term): 5 to 10 mg/kg/day divided q6h to q8h
- Infants and Children (>1 month): 20 to 40 mg/kg/day divided q6h to q8h
- Safety and efficacy in pediatric patients under 16 years are not well established for long-term use
Indications
- Treatment of active duodenal and benign gastric ulcers
- Management of gastroesophageal reflux disease (GERD)
- Treatment of pathological hypersecretory conditions (e.g., Zollinger-Ellison syndrome)
- Short-term symptomatic relief of heartburn, acid indigestion, and sour stomach
Mechanism of Action
- Competitive, reversible histamine H2-receptor antagonist on the basolateral membrane of gastric parietal cells
- Inhibits both basal and stimulated gastric acid secretion induced by histamine, gastrin, and acetylcholine
- Reduces total daily gastric acid volume and hydrogen ion concentration
Contraindications
- Hypersensitivity to cimetidine or other H2-receptor antagonists
- Concurrent use with dofetilide (risk of severe arrhythmias)
Adverse Reactions
- Common: Headache, dizziness, fatigue, diarrhea, constipation
- Endocrine: Gynecomastia, galactorrhea, impotence (due to weak anti-androgenic effects with long-term/high-dose use)
- Hepatic: Transient elevations in serum transaminases and bilirubin, hepatitis
- Hematologic: Rare cases of neutropenia, thrombocytopenia, aplastic anemia
- Renal: Elevated serum creatinine, interstitial nephritis
- CNS: Confusion, delirium, hallucinations (primarily in elderly or renally impaired patients)
Drug Interactions
- CYP450 inhibitor (potent inhibitor of CYP1A2, CYP2C19, and CYP3A4; moderate inhibitor of CYP2D6)
- Increases plasma concentrations of warfarin, phenytoin, theophylline, lidocaine, and certain benzodiazepines
- Decreases absorption of drugs requiring an acidic gastric environment (e.g., ketoconazole, atazanavir, iron salts)
- Dofetilide: Cimetidine increases dofetilide plasma concentrations, risking QT prolongation and torsades de pointes
Curated Content: Needs Vetting Before Put to Clinical Use