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si-MET-ih-deen - Pronunciation guide

Brand Names

  • Cimetidine Hydrochloride Solution
  • Cimetidine Tablets USP
  • Tagamet


Rx symbolCimetidine is an anti-ulcer medication that works as a histamine H2 receptor antagonist and prevents the stomach from producing acid. It is also used in the treatment of benign melanomas in horses.


Cimetidine is used to treat equine gastric ulcers, often found in foals and race horses, which are two populations with a higher risk for gastric ulcers than other horses. After a diagnosis of ulcers, cimetidine is usually prescribed for two to three weeks to give the ulcers time to heal. Studies show that ulcers may not heal if horses remain in training or experience stressful conditions.

Cimetidine is sometimes prescribed as a precaution to be used with nonsteroidal anti-inflammatory drugs, corticosteroids, and other drugs that can cause gastric ulcers.

Cimetidine is also used to treat melanomas in horses, either alone or in combination with surgery or immunotherapy. The recommended duration of treatment is usually three months or more.

Dosage and Administration

Prescription medicationCimetidine
Method Dosage
(click row for calculator)
Concentration Period Duration
Oral 2.5 mg/kg 200 mg/tablet 3 or 4 times a day NA
Oral 2.5 mg/kg 300 mg/tablet 3 or 4 times a day NA
Oral 2.5 mg/kg 400 mg/tablet 3 or 4 times a day NA
Oral 2.5 mg/kg 800 mg/tablet 3 or 4 times a day NA
Intravenous injection 6.6-10 mg/kg 150 mg/ml 3 or 4 times a day NA


  • Federal law restricts this drug to use by or on the order of a licensed veterinarian.
  • This drug is not approved for use in horses, but may be prescribed by a veterinarian for extra-label use.
  • Calculator is for educational purposes only. Follow your veterinarian's instructions regarding use of this, or any medication.

Dose Form: HCL injectable: 150 mg/ml

Tablets: 200 mg, 300 mg, 400 mg, 800 mg

Side Effects

Drug side effects are rare, but cimetidine should be used with caution or in smaller doses in horses with decreased liver or kidney function. In some cases, cimetidine has been associated with breathing difficulties and heart rhythm disturbances, but little is known about these cases.


Cimetidine is not FDA approved for use with horses, but is a commonly used and accepted practice when lawfully prescribed by a licensed veterinarian. Use of cimetidine is forbidden in drug-free competition. Horse owners and handlers should check with a knowledgeable veterinarian and the individual regulatory group regarding rules for therapeutic use of cimetidine.


Cimetidine may slow the metabolism of other drugs that are metabolized by the liver. Some veterinarians recommend separating oral doses of cimetidine from antacids, metoclopramide, and sucralfate. Cimetidine may also affect blood clotting in animals on warfarin.


Overdoses of cimetidine have been associated with breathing difficulties and heart rhythm disturbances, but little is known about these cases.


Cimetidine Hydrochloride SolutionCimetidine Hydrochloride Solution

Cimetidine Tablets USPCimetidine Tablets USP



About the Author

EquiMed Staff

EquiMed staff writers team up to provide articles that require periodic updates based on evolving methods of equine healthcare. Compendia articles, core healthcare topics and more are written and updated as a group effort. Our review process includes an important veterinarian review, helping to assure the content is consistent with the latest understanding from a medical professional.