Detection of nonsteroidal and steroidal selective androgen receptor modulators in equine hair after oral administrations.

This paper describes the detections of nonsteroidal and steroidal selective androgen receptor modulators (SARMs), namely, RAD140 and YK-11, in mane hair collected from horses having been orally administered with the respective drugs. SARMs are potent anabolic agents with a high potential of misuse in horseracing and equestrian sports, and the misuses of RAD140 and YK-11 in human sports have been reported. To better control the misuse of RAD140 and YK-11 in horses, two separate oral administration studies of RAD140 (0.3 mg/kg daily for 3 days) and YK-11 (0.2 mg/kg daily for 3 days) were previously conducted to investigate their metabolism and to identify target analyte(s) with the longest detection time in urine and plasma for doping control. In this work, segmental analyses of post-administration hair samples have revealed that (i) RAD140 and YK-11 could be detected in horse mane after oral administration and (ii) internal incorporation of RAD140 into hair via bloodstream and external incorporation through sweat or sebum were both observed, whereas YK-11 was primarily incorporated into hair via sweat or sebum.