Famotidine is a commonly used H2 receptor antagonist which can be found in Pepcid. It binds to H2 receptors in the stomach lining causing a lowered production of stomach acid which can improve conditions like acid reflux, though it’s mainly used to help dogs recover from internal ulcers. These internal ulcers known as peptic (or stomach) ulcers can be caused by many different things, but they most commonly develop when certain gastric structures are damaged by stomach acid, or following infection with bacteria such as H. pylori. They often develop in the gut but can also occur in the intestine quickly becoming dangerous if they bleed. Unlike other H2 antagonists such as cimetidine, this drug does not interact with any known substances and does not effect the CYP enzyme system meaning there are not as many side effects.

Ulcers, or cancer?

If you suspect stomach ulcers it’s important that you see your vet for a diagnosis. This is because some of the signs of stomach cancer can mimic the symptoms of ulcers including pain in the abdomen and loss of appetite. A formal diagnosis will be able to rule out the possibility of cancer, and also provide you with a solid treatment plan.

Recommended Dosage

Note: Always speak to your vet before giving famotidine to your dog.

The famotidine dosage most often recommended for the treatment of dogs is 0.25 to 0.5 mg/lb administered twice daily. Even though the medicine is available over-the-counter it’s still a good idea to seek your vet’s approval first. Refer to the chart below to find the typical dosage for your dog’s weight.

A dosage chart for the drug famotidine

10 mg is the most common strength of famotidine tablets, though 20 mg pills are also available for use. When treating ulcers caused by H. pylori a course of antibiotics will also be required, with treatment usually lasting between one and two weeks.

Example: A 40 lb dog would need one 10 mg pill every 12 hours. On the higher end of the scale they would need 20 mg twice daily.

Is It Safe?

Famotidine is safe for most dogs and can be obtained at most local pharmacies. It is not currently FDA-approved for use in dogs, however, it is still prescribed often due to its advantages over other common H2 receptor antagonists.

The drug has not yet been tested in regards to pregnancy, but it has been shown to pass through breast milk in trace amounts. Though the amount passed through milk is very small the manufacturers suggest avoiding use in nursing animals unless absolutely necessary.

Contraindications & Interactions:

Dogs with the following medical conditions may be unsuitable for treatment:

  • Kidney problems
  • Liver problems
  • Stomach cancer
  • Sensitivity to other H2 receptor antagonists

It is believed that no interactions exist between famotidine and other drugs making it a safe treatment option for dogs who are on other medication.

Safety Guidelines

Famotidine lacks drug interactions making it safe for use in most cases. However, you should still notify a vet prior to use, and should also seek a formal diagnosis for peptic ulcers in case of cancer. Always tell the vet about any medical conditions your dog suffers from.

Ulcer safety:

If your dog has peptic ulcers, the main concern is bleeding. In these cases you should never administer NSAIDs like aspirin which thin the blood and reduce the body’s ability to form clots as doing so could lead to dangerous efffects including massive blood loss.


Pepcid is mainly indicated for the treatment of peptic ulcers, though its inhibition of stomach acid production makes it suitable for treating various other conditions related to acid levels. These conditions include:

  • Acid reflux
  • GERD
  • Heartburn
  • Esophagitis

It is also useful for the treatment of Zollinger-Ellison syndrome.

Side Effects

Your dog is unlikely to experience serious adverse reactions. However understanding the most common side effects can help keep your pet protected. Expect and be aware of the following potential sides:


  • Diarrhea
  • Constipation
  • Headaches
  • Nausea

Incidence Unknown

  • Stomach pain
  • Diminished appetite
  • Bad breath
  • Fatigue
  • Insomnia


If your pet develops any signs of a serious reaction such as difficulty breathing, wheezing or seizures, stop administering the medicine and call the vet immediately.

Symptoms of overdose:

Overdoses of famotidine are rare. If you suspect an overdose you should call the vet right away and look out for signs such as:

  • Vomiting
  • Diarrhea
  • Fatigue
  • Hypotension *
  • Abnormally low heartbeat
  • Abnormally high heartbeat
  • Breathing difficulties

* Symptoms of hypotension (low blood pressure) includes fainting, blurred vision, rapid/irregular heartbeat, dizziness and confusion.

If you have accidentally overdosed your pet or believe they have ingested an overdose, ring for emergency assistance from a vet. US and Canadian citizens can also reach the Pet Poison Helpline on 800-213-6680.