Cimetidine

Cimetidine treats gastrointestinal ulcers and acid reflux in dogs. Although it was one of the first drugs of its kind, cimetidine is usually not the first choice for treating conditions involving excess stomach acid secretion. Cimetidine may interact with or inhibit the body’s ability to absorb other medications.

Keep reading for more information on recommended dosage amounts of cimetidine for dogs, drug interactions, and other considerations.

Dosage

The standard recommended dose is 5 to 10 mg of cimetidine per kg. However, the dosage may vary depending on pre-existing conditions and the severity of your dog’s symptoms. The dosage is typically reduced for dogs with kidney or liver disease, as the drug’s effects last longer in their system. Consult your veterinarian for dosage instructions. 

Cimetidine is typically administered 2 to 4 times per day, at least 30 minutes before a meal. Cimetidine is most effective when administered on an empty stomach. If your dog vomits or refuses to take it, try giving it with a small amount of food or a treat.

Efficacy

The first drug of its class for veterinary use, cimetidine was once the gold standard for treating gastrointestinal disorders involving excess stomach acid secretion. However, it has fallen out of favor with many veterinarians due to its interactivity with other drugs. It is also less effective than famotidine in suppressing gastric acid secretion.

Active ingredients in cimetidine

Cimetidine is an antihistamine that binds to the H-2 receptors in the stomach to suppress acid production. This allows stomach ulcers to heal and relieves other symptoms such as erosion of the stomach lining.

Side effects

Few side effects have been observed in dogs taking cimetidine. Elderly dogs taking cimetidine may experience confusion. Cimetidine is also thought to worsen heartbeat irregularities in dogs diagnosed with heart arrhythmias. If you notice any adverse effects or signs of an allergic reaction, contact your veterinarian right away.

Considerations

Elderly dogs — as well as those with blood disorders, kidney disease, and liver disease — should use cimetidine with caution. Cimetidine can also skew the results of skin and allergen tests. If your dog is scheduled for a test, let your vet know if they are taking cimetidine.

Drug interactions

The list of drugs that interact with cimetidine is a long one. Cimetidine affects the body’s ability to eliminate these drugs, thereby prolonging, strengthening, or weakening their effects, depending on the drug. Possible drug interactions include:

• Opioids

• Antacids 

• Benzodiazepines

• Anesthetics (lidocaine)

• Allergy medications (loratadine)

• Appetite stimulants (mirtazapine)

• Immunosuppressants (cyclosporine)

• Blood thinners (clopidogrel, warfarin)

• Anti-worm medications (praziquantel)

• Respiratory medications (theophylline)

• Diabetes medications (glipizide, glyburide)

• Urinary medications (tamsulosin, triamterene)

• Other acid reflux medications (cisapride, domperidone)

• Cancer treatments (fluorouracil, myelosuppressive drugs)

• Antibiotics (cefpodoxime, chloramphenicol, metronidazole)

• Antidepressants (mirtazapine, SSRIs, tricyclic antidepressants)

• Antifungal medications (itraconazole, ketoconazole, terbinafine)

• Anti-seizure and anti-epileptic medications (carbamazepine, phenytoin)

• Heart and blood pressure medications (beta-blockers, calcium channel blockers, procainamide, quinidine, sildenafil, tolazoline)

If your dog is taking any medications on a regular basis, including over-the-counter supplements, be sure to tell your vet.

Allergic reactions and sensitivity

Though rare, it is possible for dogs to be allergic to cimetidine and similar antihistamines that suppress stomach acid secretion. If you notice signs of an allergic reaction, contact your veterinarian immediately.

Frequently asked questions

What does cimetidine for dogs treat?

Cimetidine is most effective in treating gastrointestinal symptoms associated with the following conditions, including:

• Chronic vomiting

• Gastritis

• Nausea

• Acid reflux

• Canine parvovirus

• Ingestion of toxins that cause stomach ulcers

• Stomach and intestinal ulcers

• Inflammatory bowel disease

• Inflammation or erosion of the stomach lining

Do I need a prescription for cimetidine?

Cimetidine for dogs is available over-the-counter and as a prescription. However, because it interacts with a wide variety of drugs, you should consult your veterinarian before administering cimetidine. 

My vet prescribed the liquid form of cimetidine. Do I need to refrigerate it?

Liquid cimetidine does not need to be refrigerated. It should be stored at room temperature.

What should I do if I miss a dose?

Give the next dose as soon as you remember, unless it’s within a few hours of the next dose. In this case, skip the missed dose and return to your regular dosing schedule. It’s important to administer all medications according to your vet’s instructions. Setting a reminder can help you remember to give your dog their medication on time.

Is it possible to overdose on cimetidine?

Overdose is extremely unlikely. Always keep medications out of your dog’s reach, and never give more than the prescribed amount.