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Bute, Phenylbutazone

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Phenylbutazone (bute) is an extremely useful and practical prescription drug that is commonly used in equine veterinary practice. Bute has been around for decades and is very effective for a variety of conditions, especially those involving the musculoskeletal system. It is also used (less often) in other species.

Bute is somewhat less effective than Banamine® (flunixin) in treating abdominal pain (colic), but it can still be useful.

Bute is supplied in pastes, powders, and tablets. In addition, Bute may be given as an intravenous injection.

Bute is in the same drug class as ibuprofen, flunixin meglumine and acetaminophen, the so-called NSAIDS (non-steroidal anti-inflammatory drugs), which work by reducing the formation of prostaglandins, a group of molecules that take part in inflammation. The inflammatory pathways also lead to swelling and pain. By reducing prostaglandin formation, pain and inflammation (swelling and redness) is decreased also.

However, there are a number of “good” or “housekeeping” prostaglandins that perform protective functions in the body. Bute eliminates these also, and this exposes certain body systems to injury. The two organs in horses that tend to be damaged by NSAIDS are the intestine and the kidney.

Although this drug requires a vet’s prescription, many horse owners keep a tube of bute handy to treat their horses when they see signs of lameness, swelling or less commonly abdominal pain (colic).

The problem is that horse owners often do not understand the benefits and limitations of this drug, and/or do not know what the underlying diagnosis is that they are treating. As a result, horse owners may use this drug inappropriately, and this can be life-threatening to a horse.

At minimum you should consult with your vet before you administer this drug to your horse. Depending on the problem, your vet may need to examine your horse, they may prescribe a different treatment, or they will provide you with careful guidelines for the use of bute.

In colic cases, bute may appear to resolve the problem, giving horse owners false confidence as the disease process continues or worsens. It is true that bute may help to resolve a simple spasmodic or “gas” type colic, but it may only provide temporary relief in more complicated or severe cases.

On numerous occasions, I have been called by a horse owner that thought bute “fixed” the colic, but their horse returns to pain after it wears off or, even worse, they find their horse dead the next day. This warning applies even more to Banamine®, which is more commonly used by horse owners without veterinary guidance in cases of colic, and carries even greater risk of masking a problem.

Consider Potential Side Effects & Complications

Bute is unsafe at high doses for long periods of time and can cause colonic ulcers (right dorsal colitis), gastric ulcers and kidney damage.

Signs of adverse reaction include diarrhea, salivation, oral ulceration, lethargy, weight loss, rough coat, loss of appetite, and change in urination habits.

Intravenous formulations of bute cause severe tissue damage if injected into the muscle or outside of the vein. For this reason, it should only be injected by a licensed vet or vet tech.

Bute is an effective enough pain reliever that in some cases, it may cause a horse to move more than it should, causing further injury. Bute may also mask the signs of an injury, causing an observer to underestimate the severity of the injury.

For all these reasons, bute should only be used under the supervision of a vet.

Consider Reasons Not To Use This Treatment

Bute should not be used in horses with an allergy to it. It is usually not used in horses with a history of kidney disease, bone marrow disease or gastrointestinal ulceration.

Generally, bute is not thought to be safe in foals.

It is not safe to use bute in combination with other NSAIDS. Bute may interact with or alter the effect of other drugs. It is used with other drugs only under veterinary supervision.

Is It working? Timeframe for effect

Given orally, you should see improvement in pain within about 30-60 minutes,. Peak effectiveness occurs at about 6 hours and gradually drops over time.

In cases of colic, the pain relieving effects drop off at about 6 hours. In cases of lameness, its effects drop off between 12-24 hours. Horses that are given bute long-term do accumulate higher levels that take longer to drop.

Signs of adverse reaction include diarrhea, depression, loss of appetite, and change in urination habits. If you notice even subtle problems, contact your vet immediately.

Questions To Ask My Vet

  • Should I be concerned about long-term side effects from the use of bute?
  • Are there any long-term safer alternatives?
  • How should I monitor my horse for some of the potential side effects?
  • What signs would I see that could indicate bute side effects?
  • How much improvement should I expect to see in my horse on bute?

Helpful terms & topics in HSVGWritten, Reviewed or Shared by Experts in Equine Health

A & G Pharmaceutical Inc. Equizone™, Palatable Phenylbutazone Flavored Powder
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Author: Doug Thal DVM Dipl. ABVP

RELATED REFERENCES

Plumb, DC. Veterinary Drug Handbook 7th Ed. Ames: Wiley Blackwell 2011.

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