Hi John . These cheats know exactly how to get their horses to the track with the use of these drugs without getting a positive . The 30 or so that have been caught are blokes just trying to keep up and they can't . Lance Armstrong got away with it since 1996 and they have only detected the masking agent which , beleive it or not , was a form of EPO which masks the use of other drugs after 24 hours . So they have to be caught working up on these drugs or straight after a booster shot .