By Rania Gollakner, BS, DVM, MPH

What is cimetidine?

Cimetidine (brand name: Tagamet®) is an over-the-counter histamine2 blocker used to reduce acid production in the gastrointestinal tract in order to treat or prevent stomach or intestinal ulcers, stomach inflammation and erosion due to kidney disease, stress or drug reactions, acid reflux, or esophageal inflammation.

Its use in cats, dogs, small mammals, and horses to treat stomach acid disorders is ‘off label’ or ‘extra label’. Many drugs are commonly prescribed for off label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully as their directions may be significantly different from those on the label.

How is cimetidine given?

Cimetidine is given by mouth in the form of a tablet or liquid solution. Give this medication about 30 minutes prior to a meal, usually in the morning. If vomiting occurs when dosed on an empty stomach, give future doses with a meal. Measure liquid forms carefully. Do not switch forms of this medication without consulting your veterinarian as the dosages may be different.

This medication should take effect within 1 to 2 hours, and improvements in clinical signs should follow.

What if I miss giving my pet the medication?

If you miss a dose, give it when you remember, but if it is close to the time for the next dose, skip the dose you missed and give it at the next scheduled time, and return to the regular dosing schedule. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

Side effects are uncommon and are not well documented in animals. Side effects reported in humans that may be seen in animals include confusion and headache. In cats, drooling may occur due to the taste of the medication.

This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this medication?

Do not use cimetidine in pets that are allergic to it or other histamine2 blockers. Use cautiously in geriatric pets or those with liver or kidney dysfunction. Use cautiously in pregnant and/or lactating pets, as safety has not been established.

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with cimetidine: antacids, benzodiazepines, beta-blockers, calcium channel blockers, carbamazepine, cefpodoxime, chloramphenicol, cisapride, clopidogrel, cyclosporine, domperidone, doxepin, fluorouracil, glipizide, glyburide, itraconazole, ketoconazole, lidocaine, loratadine, metronidazole, mirtazapine, myelosuppressive drugs, opioids, pentoxifylline, phenytoin, praziquantel, procainamide, quinidine, sildenafil, SSRIs, Tamsulosin, theophylline, terbinafine, tolazoline, triamterene, tricyclic antidepressants, or warfarin.

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.

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is there any monitoring that needs to be done with this medication?

There is no specific monitoring that needs to be done while your pet is taking this medication. Your veterinarian may monitor your pet to be sure that the medication is working. Monitor your pet at home for serious side effects.

How do I store cimetidine?

Store the tablet form of this medication at room temperature and protected from light and moisture. Follow the directions on the bottle of the liquid form of the medication.

What should I do in case of emergency?

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.

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