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Equine Health Resource

Phenylbutazone, Bute Trial



Phenylbutazone (bute) is an analgesic (pain reliever) and a non-steroidal anti-inflammatory (NSAID) that is commonly used for the treatment of lameness in horses. The short term use of bute “a bute trial” is often performed when pain is suspected as a reason for performance related limitations or problems.

Talk to and work with your vet when using this diagnostic, as it requires a team approach. Your vet may want to perform a lameness exam first, to help establish an objective baseline by which the results of this trial is evaluated.

Before bute is given, an objective baseline is established. Your vet evaluates the horse’s performance when asked to perform the maneuvers and patterns that are problematic. You should also evaluate your horse’s response carefully and objectively. Do this over 2-3 days, being as consistent as possible by performing the maneuvers in the same setting and in the same way each time.

Bute is then administered to the horse, usually 2 grams once, then 1 gram every 12 hours for 3-4 days for an average 1000 lb horse, or as recommended by your vet. For the next several days, perform the same maneuvers and patterns during this time, in order to help determine whether there is any improvement in your horse’s performance.

If there is improvement, the problem is likely pain-related and additional diagnostics provided by your vet may be recommended.


A bute trial is an inexpensive and noninvasive way to confirm that pain, rather than behavioral issues or vices, are causing the performance related problems.


This test is somewhat inexact given the difficulty horse owners have in objectively evaluating the results. Your assessment is only be as good as your interpretation. Involve your vet at the outset for a more objective, and possibly more accurate, analysis.

Do not maintain your horse on bute for long periods of time without the advice of your vet. It is unsafe in all horses at high doses for extended periods of time.


  • How should we proceed to secure the most objective and helpful results in performing this diagnostic?
  • What other diagnostics do you suggest before we do a bute trial?
  • Author: Doug Thal DVM Dipl. ABVP


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