Phenylbutazone, often referred to as "bute",[1] is a nonsteroidal anti-inflammatory drug (NSAID) for the short-term treatment of pain and fever in animals.

[5] It is used for the following purposes: In the 1968 Kentucky Derby, Dancer's Image, the winner of the race, was disqualified after traces of phenylbutazone were allegedly discovered in a post-race urinalysis.

Owned by prominent Massachusetts businessman Peter D. Fuller and ridden by jockey Bobby Ussery, Dancer's Image was the first horse to win the Kentucky Derby and then be disqualified.

About 20% of adult dogs are affected with osteoarthritis, which makes the management of musculoskeletal pain a major component of companion animal practice.

Gastrointestinal-protectant drugs, such as misoprostol, cimetidine, omeprazole, ranitidine, or sucralfate, are frequently included as a part of treatment with any NSAID.

Overdose or prolonged use can cause gastrointestinal ulcers, blood dyscrasia, kidney damage (primarily dose-dependant renal papillary necrosis), oral lesions if given by mouth, and internal hemorrhage.

[13] Effects of gastrointestinal damage include edema of the legs and belly secondary to leakage of blood proteins into the intestines, resulting in decreased appetite, excessive thirst, weight loss, weakness, and in advanced stages, kidney failure and death.

Phenylbutazone displaces warfarin from plasma binding sites, and toxic blood levels leading to haemorrhage can occur.

High doses of phenylbutazone may be considered a rules violation under some equestrian organizations, as the drug may remain in the bloodstream four to five days after administration.

Maekawa et al. (1987) found no increased cancer incidence in DONRYU rats fed a diet containing 0.125% or 0.25% phenylbutazone over two years.

[19] The World Health Organization's International Agency For Research On Cancer (IARC) stated in 1987 that there was inadequate evidence for a carcinogenic effect in humans.

Phenylbutazone may affect blood levels and duration of action of phenytoin, valproic acid, sulfonamides, sulfonylurea antidiabetic agents, barbiturates, promethazine, rifampicin, chlorpheniramine, diphenhydramine, and penicillin G.[22] Overdoses of phenylbutazone can cause kidney failure, liver injury, bone marrow suppression, and gastric ulceration or perforation.