Kentucky Derby winner Medina Spirit tests positive for banned substance. Trainer Bob Baffert said Sunday morning Medina Spirit tested positive for the anti-inflammatory drug betamethasone after winning the Kentucky Derby on May 1 at Churchill Downs, a result that ultimately could lead to the horse's disqualification. Baffert, a seven-time Derby winner, disputed the positive test result and said he still plans to enter Medina Spirit in Saturday’s Preakness at Pimlico in Baltimore. Ref. USAToday.