Bute is commonly used in the USA on racehorses and is not illegal, although it is illegal to use it on UK racehorses, it has been administrated, by unscrupulous ,vets ,trainers and staff, before and probably still is,for those Willing to take the risk!!!! There is no known drug which will make a horse RUN FASTER, just drugs to make them run up to to there very best of there ability.Although horses are drug tested at all racetracks, it is only done at random. As I said previous it is still being detected in horse meat, for human consumption,that has gone through the correct slaughter procedure!!!!!!! Ps bute is legal to administrate to horses in the UK..but not as in racehorses...Phenylbutazone, or ‘bute’ was banned for human consumption because it can slow white blood cell production and cause aplastic anaemia.