By Rania Gollakner, BS, DVM, MPH

What is phenylbutazone?

Phenylbutazone (brand names: Butazolidin®, VetriBute®, Butatron®, Phenylbute®) is a nonsteroidal anti-inflammatory drug (NSAID) used to treat pain and inflammation in pet animals only; it is not used in farmed animals.

While its use in horses is FDA-approved, its use in dogs to treat pain and inflammation is ‘off label’ or ‘extra label’. Many drugs are commonly prescribed for off label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully as their directions may be significantly different from those on the label.

How is phenylbutazone given?

Phenylbutazone is given by mouth in the form of a tablet, powder, paste, or granules. It may also be given as an injection into the vein by your veterinarian. Give this medication with food. Make sure your pet has access to water at all times while giving this medication.

This medication will take effect quickly, in about 1 to 2 hours, and improvement in clinical signs should follow.

What if I miss giving my pet the medication?

If you miss a dose, give it when you remember, but if it is close to the time for the next dose, skip the dose you missed and give it at the next scheduled time, and return to the regular dosing schedule. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

Serious side effects include skin sores, especially on the face and inside the mouth, changes in eating/drinking, changes in urination, yellowing of the skin, gums, or eyes, swelling of the legs, weight loss, behavior change, or abnormal bleeding.

This moderate-acting medication should stop working in a few days, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this medication?

Do not use phenylbutazone in pets that are allergic to it, or in pets with bone marrow disease, bleeding disorders, stomach or intestinal ulcers, or those that are pregnant unless it is completely necessary. Use cautiously in foals and ponies, pets with kidney disease, heart disease, or pets that are nursing.

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with phenylbutazone: angiotensin-converting-enzyme (ACE) inhibitors, corticosteroids, digoxin, furosemide (and other loop diuretics), hepatotoxic drugs, methotrexate, misoprostol, NSAIDs, penicillamine, penicillin G, phenobarbital, potassium-sparing diuretics, sulfonamides, tricyclic antidepressants, selective serotonin reuptake inhibitor (SSRIs), or warfarin.

Phenylbutazone also interacts with thyroid function tests.

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is there any monitoring that needs to be done with this medication?

Your veterinarian may monitor your pet to be sure that the medication is working. Regular monitoring of  blood cell counts, protein levels, kidney function, and urinalysis should be performed, especially with long-term use. Complete blood cell counts should be performed weekly at first, and then bi-weekly. Monitor your pet at home for serious side effects.

How do I store phenylbutazone?

Store the oral forms in tight containers at room temperature, between 59°F and 86°F (15°C and 30°C), and do not exceed 104°F (40°C). Store the injectable form in the refrigerator between 46°F and 59°F (8°C and 15°C). Protect from light.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.

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