Corticosteroids are the mainstay of joint treatment in performance horses and are used routinely. However, there are regulations governing the use of these drugs in performance horses in various events, and it is important to make sure your horses does not have excessive cortisone in the blood when tested. Due to their potent antiinflammatory effects, using corticosteroids close to the time of competition is illegal due to its ability to mask injuries. After being injected in a joint, several of the common corticosteroids have been tested at a certain level, and we have found an appropriate timeframe during which the horse must not be used in an event after being injected. That period of time is seven days for triamcinolone, 21 days for Depo-Medrol, and seven days for betamethasone; those are the three most commonly used drugs with which to inject horse joints. Since there is no actual recommended dosage of these drugs and there is no actual limit for the number of joints injected, the horses could be injected with these drugs and show positive on drug tests, which could cause disqualification.
A study was published in Equine Veterinary Education that studied the use of several different corticosteroids injected in multiple joints either alone or separately and found that triamcinolone and Depo-Medrol were cleared at seven and 21 days respectively as expected. However, betamethasone was detected above normal limits up to 10 days after joint injection, not seven. So all of this means that if you are showing performance horses and are injecting their joints, it is important to know the product used and the withdrawal period of the drug.