“…In May 2014, aromatase inhibitors have been listed as one of the classes of hormone and metabolic modulators (Article 6E of the International Agreement of Breeding, Racing, and Wagering) which are prohibited to be administered to racehorses at any time in their career [11]. The metabolism of ATD has been reported in human [10,12], and the in vitro metabolic study of ATD in horses has been reported [13], but little is known about its biotransformation and elimination in horses. This paper describes the investigation of the in vitro and in vivo metabolism of ATD in horses with an objective to identify the most appropriate targets for detecting ATD administration.…”