Phenylbutazone, or commonly called "bute" is an anti-inflammatory drug useful for swelling, musculoskeletal pain, and fever. Probably the most commonly used medication in horses, bute is effective and safe when used according to label directions. This article is about the contraindications, toxic effects, dosages, comparison to other NSAID's, and association drug rules that apply to phenylbutazone.

Possible contraindications for the use of phenylbutazone would be gastric ulcers, untreated dehydration, renal disease, and the concurrent use of other NSAID's. It should be used cautiously in pregnant and nursing mares as though problems are rarely reported safe dosages have not been established. Flunixin may be a better choice in these mares.

Phenylbutazone should be used carefully in older horses, foals, and ponies as they seem to be more sensitive to the toxic effects. Lower doses or less frequent dosing is recommended for these groups. TMP/SMZ, trimethoprim sulfas, and sulfa drugs may increase the blood levels of bute so reduced dosages should be used in the presence of these drugs.