Phenylbutazone is commonly used for pain in some racehorses prior to a race, but this practice could increase the chance of fatal injuries. A recent paper out of Argentina examined the use of phenylbutazone, commonly called bute, and the risk of musculoskeletal and fatal injuries in thoroughbred racehorses. Phenylbutazone is an anti-inflammatory medication that reduces pain and inflammation in horses, and at this point it is not a prohibited substance in the horse’s blood while racing in the United States. However, the last dose of bute can be given no less than 48 hours before the race and a maximum small amount of the drug is allowed in the horse’s system after a race.
In a study recently published in the AVMA Journal out of Argentina on almost 300,000 race starts, horses that recently received bute were identified as being at a significantly increased risk of musculoskeletal injuries leading to fatalities. The fatalities occurred not from the drug but from injuries received while racing that required euthanasia, and horses given bute before the race were twice as likely to have an injury that led to euthanasia. The study’s authors believe that many horses given bute are older ones with chronic disease that may increase their chances of injury. Also, the horses given bute are painful and lame to some degree as this is the reason they need bute to compete. Bute decreases pain and allows the horses to potentially run faster and increases the chance they can hurt themselves by taking away the pain.