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cimetidine
Tagamet, Tagamet HBOTC

cimetidine hydrochloride
Tagamet HCl

Pregnancy Risk Category B

How supplied
Tablets:
100 mgOTC, 200 mg, 300 mg, 400 mg, 800 mg
Oral liquid:
300 mg/5 ml
Injection:
300 mg/2 ml; 300 mg in 50 ml normal saline solution

Action
Competitively inhibits action of H2 at receptor sites of the parietal cells, decreasing gastric acid secretion.

Indications & dosage
Short-term treatment and maintenance of duodenal ulcer-

Adults and children ages 16 and older:
800 mg P.O. h.s. Or, 400 mg P.O. b.i.d. or 300 mg q.i.d. (with meals and h.s.) or 200 mg t.i.d. with a 400-mg h.s. dose. Treatment continued for 4 to 6 weeks unless endoscopy shows healing. For maintenance therapy, 400 mg h.s. For parenteral therapy, 300 mg diluted to 20 ml with normal saline solution or other compatible I.V. solution by I.V. push over at least 5 minutes q 6 hours; or 300 mg diluted in 50 ml D5W or other compatible I.V. solution by I.V. infusion over 15 to 20 minutes q 6 hours; or 300 mg I.M. q 6 hours (no dilution needed). Parenteral dosage increased by giving 300-mg doses more frequently to maximum daily dose of 2,400 mg, p.r.n.; or, 900 mg/day (37.5 mg/hour) I.V. diluted in 100 to 1,000 ml of compatible solution by continuous I.V. infusion.
Active benign gastric ulceration-

Adults:
800 mg P.O. h.s., or 300 mg P.O. q.i.d. (with meals and h.s.) for up to 6 weeks.
Pathologic hypersecretory conditions (such as Zollinger-Ellison syndrome, systemic mastocytosis, and multiple endocrine adenomas)-
Adults and children ages 16 and older:
300 mg P.O. q.i.d. with meals and h.s.; adjusted to patient needs. Maximum oral daily dose is 2,400 mg.
For parenteral therapy, 300 mg diluted to 20 ml with normal saline solution or other compatible I.V. solution by I.V. push over at least 5 minutes q 6 hours; or 300 mg diluted in 50 ml D5W or other compatible I.V. solution by I.V. infusion over 15 to 20 minutes q 6 hours. Parenteral dosage increased by giving 300-mg doses more frequently to maximum daily dose of 2,400 mg, p.r.n.
Gastroesophageal reflux disease-

Adults:
800 mg P.O. b.i.d. or 400 mg q.i.d. before meals and h.s. for up to 12 weeks.
Prevention of upper GI bleeding in critically ill patients-

Adults:
50 mg/hour by continuous I.V. infusion for up to 7 days; 25 mg/hour to patients with creatinine clearance below 30 ml/minute.
Heartburn--

Adults:
200 mg (Tagamet HB only) P.O. with water as symptoms occur, or as directed, up to b.i.d. Maximum daily dose is 400 mg. Drug shouldn't be taken daily for more than 2 weeks.
Adjust-a-dose:
For patients with creatinine clearance less than 30 ml/minute, decrease dosage to 300 mg P.O. or I.V. q 12 hours.

Adverse reactions
CNS:
confusion, dizziness, headache, peripheral neuropathy, somnolence, hallucinations.
GI:
mild and transient diarrhea.
GU:
transient elevations in serum creatinine levels, impotence, mild gynecomastia if used longer than 1 month.
Hepatic:
increased serum alkaline phosphatase levels.
Musculoskeletal:
muscle pain, arthralgia.
Other:
hypersensitivity reactions.

Interactions
Drug-drug.
Antacids: interference with cimetidine absorption. Separate administration by at least 1 hour if possible.
Lidocaine, phenytoin, propranolol, some benzodiazepines, theophylline, warfarin:
inhibited hepatic microsomal enzyme metabolism of these drugs. Monitor serum levels.
Drug-herb.
Guarana: may increase caffeine serum levels or prolong serum caffeine half-life. Monitor patient.
Pennyroyal:
may change rate of formation of toxic metabolites of pennyroyal. Monitor patient.
Yerba maté
: may decrease clearance of yerba maté methylxanthines and cause toxicity. Use together cautiously.

Effects on diagnostic tests
Drug may antagonize pentagastrin's effect during gastric acid secretion tests; it may cause false-negative results in skin tests using allergen extracts.
  FD and C blue dye #2 used in Tagamet tablets may impair interpretation of Hemoccult and Gastroccult tests on gastric content aspirate. Wait at least 15 minutes after tablet administration before drawing sample and follow test manufacturer's instructions closely.

Contraindications
Contraindicated in patients with hypersensitivity to drug.

Nursing considerations

I.V. administration

Patient teaching

*Liquid contains alcohol. **May contain tartrazine.  †Canada  ‡Australia  §U.K.  OTCOver the counter
Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE-THREATENING

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