Famotidine (Pepcid®)

Stephanie Howe, DVM
Vet Reviewed
By Stephanie Howe, DVM on Jan. 31, 2023
Famotidine (Pepcid®)



PetMD’s medications content was written and reviewed by veterinary professionals to answer your most common questions about how medications function, their side effects, and what species they are prescribed for. This content shouldn’t take the place of advice by your vet.

What is Famotidine?

Famotidine is an antacid commonly used to reduce stomach acid production in the treatment and prevention of stomach ulcers in dogs and stomach ulcers in cats. It may be used as an additional medication to treat stomach ulcers in horses.  Famotidine is also used to treat and prevent stomach ulcers in cattle and small mammals.

Famotidine is FDA-approved for human use as a generic medication and under the brand name Pepcid®. Famotidine is currently not FDA-approved as a veterinary medication. However, it is readily utilized in the veterinary field and veterinarians can legally prescribe certain human drugs for use in animals in certain circumstances. This is called extra-label or off-label use because this use isn’t described on the drug label.

How Famotidine Works

Famotidine belongs to a class of medications called H2 blockers. H2 blockers decrease the amount of acid made in the stomach by blocking the effect of histamine on H2 receptors located along the stomach wall. Histamine is the chemical messenger that tells the cells in the stomach to release gastric acid into the stomach to digest food.

In certain circumstances, your veterinarian may recommend a compounded formulation of famotidine. Compounded medications are prescribed if there’s a specific reason your pet’s health can’t be managed by an FDA-approved drug, such as if your pet has trouble taking pills in capsule form, the dosage strength is not commercially available, or the pet is allergic to an ingredient in the FDA-approved medication. Compounded medications are not FDA-approved. They are created by either a veterinarian or a licensed pharmacist on an individual basis to best suit a patient’s particular needs. You can learn more about compounded medications here.

Famotidine Directions

Follow the directions on the drug label or as provided by your veterinarian. Dosages will depend on the type of pet but are typically given once or twice daily.

Famotidine is best given on an empty stomach, before the first meal of the day. If your pet has stomach upset when given this medication on an empty stomach, it can be given with a treat or a small amount of food.

Missed a Dose

Speak with your veterinarian about what to do if you forget to give a dose of famotidine. Generally, they may advise you to give it when you remember, or if it is almost time for your next dose, to skip the missed dose and resume your normal dosing schedule. In most cases, do not give extra or double doses.

Famotidine Possible Side Effects

Famotidine is usually well tolerated and side effects from this medication are rare. Side effects, when seen, may include:

  • Lack of appetite

  • Vomiting

  • Diarrhea

Human Side Effects

While this is a human prescription medication, there are different dosages and side effects that can occur in humans.  If you accidentally ingest a pet medication, call your physician or the national Poison Control Center hotline at 800-222-1222.  


No specific monitoring is required for this medication, but your veterinarian may recommend routine testing depending on your pet’s individual needs, other medications they may be on, and/or the issue that initially caused your pet to be placed on this medication.

Call Your Vet If:

  • Severe side effects are seen (see above)

  • Your pet’s condition worsens or does not improve with treatment

  • You see or suspect an overdose

  • You have additional questions or concerns about the use of famotidine

Famotidine Overdose Information

While famotidine has a wide margin of safety, overdoses are still possible and symptoms are dependent on the amount ingested. Moderate overdoses may cause vomiting, pale gums, drowsiness, restlessness, and a red tint to the ears and areas around the mouth. Large overdoses can cause low blood pressure, high heart rate, and collapse.

If you suspect an overdose, immediately contact your veterinarian, seek emergency veterinary care, or contact an animal poison control center. Consultation fees often apply.

Pet Poison Helpline (855) 764-7661

ASPCA Animal Poison Control (888) 426-4435

Famotidine Storage

Famotidine should be stored at controlled room temperatures between 68-77 F. Always confirm storage temperatures by reading the label. Keep the container tightly closed to protect from moisture and light.

Compounded medications should be stored according to the compounding pharmacy’s label.

Keep out of reach of children and pets.

Famotidine FAQs

How long does it take famotidine take to work in dogs?

Famotidine starts working in your dog’s system within the first 1-3 hours after administration. Depending on the reason that your pet was placed on this medication, symptoms should noticeably improve within the first few days.



Stephanie Howe, DVM
Vet Reviewed


Stephanie Howe, DVM


Dr. Stephanie Howe graduated from the University of Florida College of Veterinary Medicine in 2011, after receiving a Bachelor of Science...

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