Phenylbutazone

What is phenylbutazone?

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

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. However, if it is close to the time for the next dose, skip the dose you missed, give it at the next scheduled time, and return to the regular dosing schedule. Never give two doses at once or give extra doses.

Are there any potential side effects?

SERIOUS ADVERSE REACTIONS associated with this drug may occur without warning and could, in rare cases, lead to death. If any of the following signs develop, stop giving phenylbutazone and contact your veterinarian immediately: 

• skin sores, especially on the face and inside the mouth
• changes in eating/drinking or changes in urination
• yellowing of the skin, gums, or eyes
• swelling of the legs
• weight loss
• behavior change
• 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?

Phenylbutazone SHOULD NOT BE USED in pets that:

• are allergic to it
• have bone marrow disease
• have bleeding disorders
• have stomach or intestinal ulcers
• are pregnant, unless it is completely necessary

Phenylbutazone SHOULD BE USED CAUTIOUSLY in:

• foals and ponies
• pets with kidney disease or heart disease
• pets that are nursing

Are there any drug interactions I should be aware of?

Certain medications may interact with phenylbutazone, so it is important to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your horse is taking before starting any new treatment. Medications that should be used with caution when given with phenylbutazone include: 

• corticosteroids (e.g., prednisone, dexamethasone)
• furosemide (Lasix®)
• NSAIDs
• penicillin G
• phenobarbital

Phenylbutazone also interacts with thyroid function tests.

Is any monitoring needed with this medication?

• Your veterinarian should perform baseline bloodwork and urinalysis before your pet starts phenylbutazone.
• If your pet is taking phenylbutazone for extended periods, your veterinarian will do periodic blood and urine tests to check blood cell counts, protein levels, and kidney function. Complete blood cell counts should be performed weekly at first, and then biweekly. It is very important to attend these follow-up appointments.
• Your veterinarian may recommend recheck examinations to ensure the medication is working adequately to manage pain.
• At home, monitor for any side effects such as those noted above. If any side effects occur, discontinue the medication and contact your veterinarian.  

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.
• Keep the container out of reach of children and pets.
• Store compounded forms of this medication according to the label.

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.