It has a half-life of about 4 hours and would do nothing for the horse 3 days out but will probably still show in the test, It was used for years without being tested for before they finally let you give it with lasix by the vet in some states. Has probably not been getting tested for again for awhile and was a compound in a bleeder shot that someone came up with. That would explain a bunch of positives all of a sudden.