Major Uses

Phenylbutazone is a non-steroidal anti-inflammatory drug used in the treatment of inflammation and pain in horses. This drug is more toxic than newer anti-inflammatory drugs and is therefore rarely still used in dogs. Phenylbutazone is generally not given to cats.

Phenylbutazone's primary use is to manage chronic inflammatory conditions and lameness in horses. It may also be used as an analgesic and antipyretic.

Common Precautions

The most common side effects associated with use of phenylbutazone include nausea, loss of appetite, and vomiting. The drug can cause significant stomach and mouth irritation. Mouth ulcers or other side effects should be reported to a veterinarian right away.

Phenylbutazone is not for use in animals intended for food.

If given in an artery, this drug can trigger seizures in horses. It should only be injected into the veins. It is not for injection under the skin or into the muscle, as it can cause pain and muscle damage. Due to its ability to inhibit enzymes needed to protect the stomach, blood cells, and kidneys, phenylbutazone should not be administered to animals with a history of stomach ulcers. Administering the drug misoprostol at the same time as phenylbutazone will help prevent adverse effects on the stomach.

Phenylbutazone should not be used in animals with anemia or a bleeding disorder; the drug can stop bone marrow from producing new blood cells. Additionally, phenylbutazone can cause kidney damage and should not be used in animals with existing kidney disease or in combination with other medications that are known to cause kidney problems. Drinking plenty of fresh water while using this medication reduces the risk of kidney damage. Because it can mask signs of lameness, phenylbutazone should not be used prior to soundness exams. It is also not for use in ponies and foals, and the drug may be toxic to these groups. Phenylbutazone has been shown to cause birth defects.

Due to the risk of potential interactions between phenylbutazone and other drugs and supplements, a veterinarian should be made of aware of all current treatments before prescribing phenylbutazone. Phenylbutazone is known to interact with furosemide, other non-steroidal anti-inflammatory drugs, penicillamine, hepatotoxic drugs, sulfanomides, warfarin, penicillin G, and others.

Phenylbutazone should not be used in animals with a known allergy or hypersensitivity to the drug. An overdose of phenylbutazone can cause severe symptoms and is considered a medical emergency. Any known or suspected overdose should be reported to a veterinarian right away.


Phenylbutazone should be stored in a light-resistant container, away from children and household pets. Phenylbutazone injection must be stored in the refrigerator, away from light.


Phenylbutazone is available as an oral powder, oral paste, and tablet. It should be given with food.

The typical dose of phenylbutazone varies depending on the reason for use and the species being treated. A veterinarian should be consulted for exact dosing information. Doses may vary in different species, when the drug is given by a different route or concurrently with other medications, and with regards to a patient's age, breed, and health status. A veterinarian's dosing instructions and/or those printed on the medication label should be followed closely.

If a dose of phenylbutazone is missed, it should be given as soon as possible. If it is almost time for the next dose, the missed dose should be skipped and the regular schedule resumed. Two doses of this medication should not be given at the same time. A double dose can be toxic.

This information is for general reference only and should not be used for the diagnosis or treatment of any condition of your pet. It's intended as a general reference, this information may not include all possible uses, precautions, directions, reactions (including allergic), drug interactions, or withdrawal times. Always consult your local veterinarian and have your pet examined for any advice concerning the diagnosis and treatment of your pet, including which products and doses are most appropriate. Any trademarks are the property of their respective owners. VetDepot is not a pharmacy. All prescription products are dispensed by our Pharmacy Partner. Article last updated 2/2014.