Current Issues in Human Sport Drug Testing: Clenbuterol, Erythropoietin and Xenon

Abstract

Of topical interest are three physicochemically distinct substances included in the World Anti-Doping Agency (WADA) prohibited list, the β-adrenergic receptor agonist clenbuterol (277 Da), the glycoprotein hormone erythropoietin EPO (30 400 Da) and the gas xenon (131 Da). Clenbuterol is also prohibited as a named substance by WADA under “anabolic agents”, but adverse findings may result too from athletes innocently eating clenbuterol-tainted meat. Under WADA rules, the principle of strict liability applies and, because there is no cut-off concentration for urinary clenbuterol, investigations are always required to ascertain the source, no matter how small the finding. The history concerning clenbuterol and anti-doping is described, as it is germane to understanding how the present position arose concerning its control. Administration of EPO is prohibited, as athletes who administer this hormone can benefit from increased oxygen carrying capacity, particularly useful in endurance sports. Various approaches are used to detect EPO doping and are reviewed in this text, but the effectiveness of low dose rHuEPO administration, its short half-life (4–12 h) and the relatively long residence time of red blood cells (more than 100 days) produced by the rHuEPO administration justifies further research to provide more sensitive analytical methodologies. The mechanism of xenon's pharmacological activity is reviewed following the publicity surrounding its reported use by Russian athletes. The hypothesis that xenon inhalation raises the EPO level in the human needs to be tested, to help support the inclusion by WADA of xenon under “erythropoiesis-stimulating agents”.