Cimetidine (Tagamet) inhibits the action of histamine at the histamine₂ (H₂) receptors of the stomach, inhibiting gastric acid secretion and reducing total pepsin output.

Brand Names

• Tagamet
• Tagamet HB, Tagamet HB Suspension

Drug class

• Histamine₂ (H₂) antagonist
• Pregnancy Category B

Therapeutic actions

Inhibits the action of histamine at the histamine₂ (H₂) receptors of the stomach, inhibiting gastric acid secretion and reducing total pepsin output.

Indications

• Short-term treatment of active duodenal ulcer
• Short-term treatment of benign gastric ulcer
• Treatment of pathologic hypersecretory conditions (Zollinger-Ellison syndrome)
• Prophylaxis of stress-induced ulcers and acute upper GI bleeding in critical patients
• Treatment of erosive GERD
• OTC use: Relief of symptoms of heartburn, acid indigestion, sour stomach

Contraindications and Cautions

• Contraindicated with allergy to cimetidine.
• Use cautiously with impaired renal or hepatic function, lactation.

Available Forms

Tablets—100, 200, 300, 400, 800 mg; liquid—300 mg/5 mL; injection—150 mg/mL, 300 mg/2 mL

Dosages

ADULTS

• Active duodenal ulcer: 800 mg PO hs or 300 mg PO qid at meals and hs or 400 mg PO bid; continue for 4–6 wk. For intractable ulcers, 300 mg IM or IV q 6–8 hr.
• Maintenance therapy for duodenal ulcer: 400 mg PO hs.
• Active gastric ulcer: 300 mg PO qid at meals and hs or 800 mg hs.
• Pathologic hypersecretory syndrome: 300 mg PO qid at meals and hs, or 300 mg IV or IM q 6 hr. Individualize doses as needed; do not exceed 2,400 mg/day.
• Erosive GERD: 1,600 mg PO in divided doses bid–qid for 12 wk.
• Prevention of upper GI bleeding: Continuous IV infusion of 50 mg/hr. Do not treat beyond 7 days (if creatinine clearance < 30 ml/min, give 25 mg/hr).
• Heartburn, acid indigestion: 200 mg as symptoms occur, up to 4 tablets/24 hr.

PEDIATRIC PATIENTS

Not recommended for children < 12 yr.

GERIATRIC PATIENTS OR PATIENTS WITH IMPAIRED RENAL FUNCTION

Accumulation may occur. Use lowest dose possible, 300 mg PO or IV q 12 hr; may be increased to q 8 hr if patient tolerates it and levels are monitored; if creatinine clearance < 30 ml/min, give 25 mg/hr IV for prevention of upper GI bleed.

Adverse Effects

• CNS: Dizziness, somnolence, headache, confusion, hallucinations, peripheral neuropathy; symptoms of brain stem dysfunction (dysarthria, ataxia, diplopia)
• CV: Cardiac arrhythmias, cardiac arrest, hypotension (IV use)
• GI: Diarrhea
• Hematologic: Increases in plasma creatinine, serum transaminase
• Other: Impotence (reversible), gynecomastia (in long-term treatment), rash, vasculitis, pain at IM injection site

Interactions

Drug-drug

• Increased risk of decreased white blood cell counts with antimetabolites, alkylating agents, other drugs known to cause neutropenia
• Increased serum levels and risk of toxicity of warfarin-type anticoagulants, phenytoin, beta-adrenergic blocking agents, alcohol, quinidine, lidocaine, theophylline, chloroquine, certain benzodiazepines (alprazolam,chlordiazepoxide, diazepam, flurazepam, triazolam), nifedipine, pentoxifylline, TCAs, procainamide, carbamazepine when taken with cimetidine

Nursing Interventions

• Give drug with meals and hs.
• Administer IM dose undiluted deep into large muscle group.
• Arrange for regular follow-up, including blood tests to evaluate effects.