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Cimetidine (brand name: Tagamet®) is an over-the-counter histamine2 (H2) blocker. Because it reduces acid production in the gastrointestinal tract, cimetidine may be recommended to treat or prevent stomach, esophageal, or intestinal ulcers or inflammation.
These conditions may occur without an identified cause or may be secondary to acid reflux, stress, drug reaction, or kidney disease.
Its use in cats, dogs, small mammals, and horses to treat stomach acid disorders is off label (extra label). Many drugs are commonly prescribed for off-label use in veterinary medicine.
“Off label” means the drug is being used in a way that has not been reviewed or approved by the U.S. Food and Drug Administration (FDA) or Health Canada. In these instances, follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label.
This medication should take effect within 1 to 2 hours, and improvements in clinical signs should follow.
If you miss a dose, give it as soon as you remember, and then continue with the regular dosing schedule. However, if it is almost time for the next dose, skip the missed dose and resume the regular dosing schedule. Do not give the pet two doses at once.
Side effects are uncommon and are not well documented in animals. Side effects reported in humans, which may be seen in animals, include:
In cats, drooling may occur due to the taste of the medication.
Other side effects may occur. If you notice anything unusual, contact your veterinarian immediately. This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.
DO NOT USE cimetidine in pets that:
USE WITH CAUTION in pets that:
Several medications should be used with caution when given with cimetidine, including:
This medication may also interfere with certain laboratory tests such as allergen skin tests; discontinue this medication at least 24 hours prior to these tests.
Certain medications may interact with cimetidine, so be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking before starting any new treatment.
If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility. Be prepared to provide information about the product and your pet’s weight and symptoms.
© Copyright 2025 LifeLearn Inc. Used and/or modified with permission under license. This content written by LifeLearn Animal Health (LifeLearn Inc.) is licensed to this practice for the personal use of our clients. Any copying, printing or further distribution is prohibited without the express written consent of LifeLearn. This content does not contain all available information for any referenced medications and has not been reviewed by the FDA Center for Veterinary Medicine, or Health Canada Veterinary Drugs Directorate. This content may help answer commonly asked questions, but is not a substitute for medical advice, or a proper consultation and/or clinical examination of your pet by a veterinarian. Please contact your veterinarian if you have any questions or concerns about your pet’s health. Last updated on Apr 3, 2025.
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