Omeprazole for Dogs, Cats, and Horses: Uses and Side Effects

Omeprazole is a medication veterinarians use to help treat and prevent stomach and upper intestinal ulcers in dogs, cats, horses, and other animals. It works by reducing the amount of acid produced in the stomach.

In horses, omeprazole is available in the FDA-approved products GastroGard® and UlcerGard®. In dogs and cats, veterinarians may prescribe omeprazole extra-label for stomach ulcers, gastritis, and certain other gastrointestinal conditions.

What Is Omeprazole?

Omeprazole is a medication used to treat and prevent ulcers in the stomach and upper portions of the small intestine in dogs, cats, ferrets, and horses.

In dogs, cats, and ferrets: Omeprazole is used off-label to treat and prevent stomach ulcers and treat gastritis. It may also be used in combination with other medications to treat Helicobacter infections or inflammatory bowel disease.

In horses: GastroGard® and UlcerGard® are oral paste formulations of omeprazole that are FDA-approved for horses and foals 4 weeks of age and older for the treatment and prevention of gastric ulcers.

Off-label use: Off-label or extra-label use means a medication is prescribed for a use or species that is not specified on the medication label. Veterinarians can legally prescribe medications off-label in certain circumstances. Your veterinarian will determine whether omeprazole is right for your pet.

Compounded omeprazole: In certain circumstances, your veterinarian may recommend a compounded formulation if:

• Your pet has trouble taking the commercially available formulation.
• The dosage strength needed is not commercially available.
• Your pet is allergic to an ingredient in the FDA-approved medication.

Compounded medications are not FDA-approved. They are created by a veterinarian or licensed pharmacist on an individual basis to best suit a patient's particular needs.

How Omeprazole Works

Omeprazole works by blocking proton pumps in the stomach, which reduces the production of excess stomach acid.

Omeprazole belongs to a class of medications called proton pump inhibitors (PPIs). Proton pumps are enzymes found in the stomach lining that help produce stomach acid for digestion.

By binding to and blocking these proton pumps, omeprazole reduces excess stomach acid, helping treat ulcers and gastritis.

How To Give Omeprazole

Give omeprazole exactly as directed by your veterinarian. It is generally given by mouth once or twice daily and is best given on an empty stomach before the first meal of the day.

General administration instructions:

• Follow the directions on the medication label or those provided by your veterinarian.
• The dosing frequency depends on your pet's species and the condition being treated.

For GastroGard® and UlcerGard® in horses:

GastroGard® and UlcerGard® are oral pastes supplied in prefilled syringes.

• Before administering, turn the ring on the syringe to the left.
• Slide the ring to the correct body weight or dose.
• Turn the ring back to the right to lock it in place.
• Make sure there is no feed in your horse's mouth before administering the paste by mouth.
• Follow your veterinarian's instructions to ensure you give the correct amount.

Missed a Dose?

If you miss a dose of omeprazole, contact your veterinarian for guidance. Generally, they may instruct you to give it when you remember. 

If it is almost time for the next dose, they may recommend skipping the missed dose and resuming the normal dosing schedule.

Do not give extra or double doses.

Omeprazole Side Effects

Side effects from omeprazole are rare, but they can occur.

Possible side effects include:

• Loss of appetite
• Colic
• Vomiting
• Gas
• Diarrhea, especially in dogs

Human Side Effects

Omeprazole is also a prescription medication for humans, but human and veterinary doses and side effects may differ.

If you accidentally ingest a pet medication, call your physician or the National Poison Control Center hotline at 800-222-1222.

Monitoring Your Pet

No specific monitoring is required for omeprazole, but your veterinarian may recommend routine testing depending on your pet's individual needs, other medications they may be taking, and the condition being treated.

When To Call Your Veterinarian

Contact your veterinarian if:

• Your pet develops severe side effects.
• Your pet's condition worsens or does not improve.
• You see or suspect an overdose.
• You have additional questions or concerns about the use of omeprazole.

Omeprazole Overdose

Significant overdoses of omeprazole are unlikely to occur, but side effects can develop if your pet receives too much medication.

Signs of an overdose may include:

• Loss of appetite
• Vomiting
• Diarrhea
• Colic

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

• Pet Poison Helpline: (855) 764-7661
• ASPCA Animal Poison Control: (888) 426-4435

How To Store Omeprazole

Store omeprazole at controlled room temperatures between 68 F and 77 F (20 C–25 C).

Storage instructions:

• Brief exposure to temperatures between 59 F and 86 F (15 C–30 C) is acceptable.
• Keep the container tightly closed to protect the medication from moisture and light.
• Always confirm storage requirements by reading the medication label.
• Keep out of reach of children and pets.