CIMETIDINE (Tagamet): What is used for?

What is Cimetidine?

Cimetidine is an active ingredient used for the treatment of gastric and duodenal ulcer, symptomatic treatment of gastroesophageal reflux, GERD, Zollinger-Ellison syndrome, prevention of Mendelson’s syndrome. The product ingredient is Cimetidine hydrochloride (hcl).

The brand names of Cimetidine in the United States are: Tagamet, Tagamet HB, Leader Heartburn Relief, Equaline Acid Reducer.

Cimetidine Mechanism of Action (MOA)

Antagonizes histamine H2 receptors from parietal cells of the stomach. Inhibits basal and food-stimulated acid secretion and reduces pepsin production. Cytoprotective.

Therapeutic Indications and Dosage of Cimetidine


TABLET: 200 mg/1, 300 mg/1, 300 mg/5mL, 400 mg/1, 800 mg/1.


– Gastric and duodenal ulcer: oral, single dose 800 mg at bedtime, or 400 mg/12 hours, or 200 or 400 mg with 3 meals and 400 mg at bedtime; gastritis: 200 mg with 3 meals and 200 mg at bedtime. Minimum 4 weeks.
Maintenance for recurrence prophylaxis: 400 mg at bedtime or 400 mg/12 hours.

– Symptomatic treatment of gastroesophageal reflux: oral, 200 mg with 3 meals, maximum 15 days.

– GERD (from heartburn to peptic esophagitis): oral, single dose 800 mg at bedtime, or 400 mg/12 hours.
Severe cases: 400 mg 4 times/day (with meals and at bedtime), 12 weeks.

– Prevention of stress ulcer in severe patients at risk of bleeding; treatment of bleeding from peptic ulcer or upper gastrointestinal tract erosions.
Intramuscular: 200 mg /4-6 hours.
Intermittent intravenous infusion (dilute 400 mg in 100 ml 5% dextrose solution or another compatible solution and infuse minimum 15 minutes, maximum 2.4 g/24 hours) or continuous (maximum 74 mg/h for 24 hours).
Intravenous slow minimum 5 minutes: dilute 200 mg in ClNa 0.9% solution or another compatible one up to 20 ml/3-6 hours, maximum 2 g/day. When the bleeding has stopped orally: 200-400 mg/4-6 hours; maximum 2.4 g/day.

– Zollinger-Ellison syndrome: oral, up to 2 g/day in 5 doses of 400 mg.

– Pancreatic insufficiency (as a complement): oral (60-90 min before meals), 0.8-1.6 g/day in 4 doses.

– Prevention of Mendelson’s syndrome: oral, 400 mg 90-120 minutes before general anaesthesia, and preferably another dose of 400 mg the night before.

Obstetrical patients: 400 mg at the start of labor followed by 200 mg/2 hours, maximum 1.6 g.
Parenteral (preferably intramuscular): 300-400 mg 1 hour before general anaesthesia, followed by 200-300 mg/4 hours.

– Reduction of malabsorption and fluid loss in short bowel syndrome: oral, maximum 1 g/day in spaced doses.

– Treatment of NSAID-induced lesions: oral, single dose at bedtime 800 mg/day or 400 mg/12 hours, 8 weeks.
If response is adequate and further treatment with NSAIDs is necessary, maintenance: 400 mg at bedtime.

Children 1-12 years:

20-40 mg/kg/day; < 1 year: 20 mg/kg/day; neonates: 5 mg/kg/day.

Divide the dose every 4-6 h.

– Severe liver failure: maximum 600 mg/day.

– Kidney failure: reduce daily dose (except with dose ≤ 400 mg/day) by 66% if Clcr = 0-4 ml/min; 50% if Clcr = 5-29 ml/min and 25% if Clcr = 30-49 ml/min.

Method of administration of Cimetidine

Take preferably with meals and in the cases indicated at bedtime. In case of administration as a complement in pancreatic insufficiency, it should be taken between 60 and 90 minutes before meals.

Contraindications of Cimetidine


Concomitance with dofetilide due to increased risk of ventricular arrhythmias (torsades de pointes).

Warnings and precautions with Cimetidine

  • Severe liver failure and kidney failure, adjust dosage.
  • Children, limited experience, not recommended except for benefit > risk, adjust dose according to age.
  • Discard malignant lesions.
  • Increased risk of developing community-acquired pneumonia in: elderly, immunocompromised, diabetic, or with chronic lung disease.
  • Concomitance with: coumarins (control prothrombin time); phenytoin, theophylline (adjust dose).
  • Worsens arthritis symptoms.
  • Mild and reversible confusional states described.
  • Avoid rapid intravenous injection (< 5 min).

Liver failure

Caution. With severe liver failure: maximum 600 mg/day.

Kidney failure

Caution. Reduce daily dose (except with dose ≤ 400 mg/day) by 66% if Clcr = 0-4 ml/min; 50% if Clcr = 5-29 ml/min and 25% if Clcr = 30-49 ml/min.

Interactions with Cimetidine

  • Increases plasma level of: tricyclic antidepressants (e.g. amitriptyline), class I antiarrhythmics (e.g. lidocaine and quinidine), Ca channel blockers (e.g. nifedipine and diltiazem), oral sulfonylureas, metoprolol, propranolol, procainamide, metformin, cyclosporine, tacrolimus, diazepam, and chlordiazepoxide.
  • Increases absorption of: atazanavir.
  • Decreases absorption of: ketoconazole, itraconazole, posaconazole.
  • Power myelosuppressor effect of: carmustine, fluorouracil, epirubicin, radiotherapy.
  • Parenteral: physical incompatibility with pentobarbital.

Pregnancy and Cimetidine

Limited experience in pregnancy.
Do not use unless benefit outweighs risk.


There are insufficient human data on the use of cimetidine during breastfeeding.
Cimetidine is excreted in breast milk, therefore it should not be administered during lactation. In the case of caesarean section in patients receiving cimetidine in conjunction with general anaesthesia, the relatively short half-life of cimetidine (2 hours) may exclude the presence of significant amounts of cimetidine in breast milk when recovery time has progressed sufficiently to allow lactation.

Effects on driving ability

Although no such effects are to be expected, if dizziness occurs, do not drive or use dangerous machinery.

Adverse reactions and side effects of Cimetidine

  • Headache,
  • Dizziness.
  • Diarrhea.
  • Skin rashes.
  • Myalgia.
  • Tiredness.


Source: The content of this active ingredient has been written taking into account the clinical and molecular information of all medicines authorised and marketed in the United States under the Unique Ingredient Identifier (UNII) by the Substance Registration System (SRS) of the Food and Drug Administration (FDA) and the United States Pharmacopeia (USP).

In order to know in detail the information authorized by the FDA for each drug, you should consult the corresponding medication guide authorized by the FDA.


UNII: 80061L1WGD
PubChem CID: 2756
NCI Thesaurus: C374


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