(cimetidine hydrochloride)


Tagamet, Cimetidine


  • Tablets: 100 mg, 200 mg (avail. in higher mg tablets as well).
  • Syrup: 40 mg/mL
  • Cimetidine HCL liquid: 300 mg/5mL


Cimetidine is an H2 receptor antagonist, which competitively blocks histamine to decrease daytime and nocturnal gastric acid secretion.

It inhibits gastric secretions stimulated by the following:  food, insulin, pentagastrin, and histamine; however, gastric emptying and lower esophageal pressure are not altered by this drug.

It has a demonstrated effect on reversal of suppressor T cell-mediated immunity.

Cimetidine is well absorbed by way of the GI tract and distributed in tissues. It is able to cross placental barrier.

It is metabolized in the liver, excreted in the kidneys, and through breast milk.


Used to treat gastric and duodenal ulceration, esophagitis and gastroesophageal reflux. Also used to treat in mega-esophagus by reducing gastric secretions.

Drug Interactions or Contraindications

  • Use cautiously in impaired hepatic and renal functions.
  • May increase serum levels of beta blocking agents, lidocaine, calcium channel blockers, benzodiazepines, metronidazole, phenytoin, quinidine, and theophylline.
  • Decreases renal clearance of procainamide.
  • May be incompatible with amphotericin B, ampicillin sodium, cefazolin sodium, pentobarbital sodium.

Adverse Reactions

CNS: disorientation

CV: cardiac arrhythmias

GI: diarrhea

Skin: pruritus (itching), pain

Blood: agranulocytosis

Dosage Recommendations

5 mg/kg to 10 mg/kg, PO, SQ, IM, q6hr to q12hr  1, 2, 27, 41, 42, 44


  • In the event of respiratory failure beta-adrenergic blockers may be given.
  • Store tablets in a tightly closed container, away from light, at room temperature.
  • Do not refrigerate injectables since they may precipitate.


Links to


The Rat Guide and its affiliates accept no responsibility for misuse or misunderstanding of its information. This guide in whole or part, exists solely for the purpose of recognizing and understanding the care and illnesses in the pet rat. Please seek advice and treatment from a qualified Veterinarian if your rat is ill.

2000 - 2023 by Karen Grant RN. All rights reserved.
All other written and visual materials used by permission of specific authors for the sole use of the Rat Guide. Please visit our Privacy Policy for details.
Brought to you by KuddlyKorner4u
See Logos page for linking to the Rat Guide.
Contact us here: Rat Guide Team
Please note: Rat Guide email is not checked daily. Send e-mail to if you have an urgent medical problem with your pet rat. When possible, it is always best to take your rat to a qualified rat veterinarian.