Clostebol and sport: about controversies involving contamination vs. doping offence.

Clostebol, the 4-chloro derivative of testosterone, available as Over The Counter product in pharmacies and drugstores in several countries, is mostly commercialized as a cream or spray in the form of acetate ester. As other anabolic steroids, clostebol is listed as a prohibited substance by the World Anti-Doping Agency (WADA). Controlled transdermal application of clostebol acetate has been reported to produce detectable amounts of its metabolites in urine, even after a single exposure. Indeed, a low urine concentration can be interpreted as the tail of a drug voluntarily used to enhance performance or a direct consequence of a contamination. The increased number of adverse analytical findings (AAFs) involving clostebol reported in the last years should lead to highlight the need for athletes to be warned against personal and /or accidental use/exposure of dermal preparation containing this doping agent. Further discussion on possible threshold limits and laboratory testing on different matrices (e.g. hair) to better clarify the origin of minimal amounts of clostebol in urines is advisable.