286 ICRAV 2026 1. Dirección Técnica, Consejo Superior de la Hípica, Santiago, RM, Chile 2. Escuela de Medicina Veterinaria, Facultad de Agronomía y Sistemas Naturales, Facultad de Ciencias Biológicas y Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Región Metropolitana, Chile 3. Racing Analytical Services Ltd, Flemington, Victoria, Australia 4. Advisory Council of Equine Prohibited Substances and Practices, International Federation of Horseracing Authorities, Hong Kong ABSTRACT Formestane is a steroidal aromatase inhibitor, prohibited at all times under the IFHA and ARCI rules. In 2023, a postrace urine sample collected from a female Thoroughbred racehorse returned positive for formestane, 4-hydroxytestosterone, and 6α-hydroxyandrostenedione, from the Official Laboratory (RASL). The initial investigation identified a commercial supplement containing dehydroepiandrosterone (DHEA) and pregnenolone, administered at twice the daily dose recommended by the manufacturer. Subsequently, the responsible person submitted a report from their private veterinary advisor claiming endogenous production, requesting threshold implementation and Isotope Ratio Mass Spectrometry (IRMS) analysis, as recommended by WADA in human anti-doping. The investigation extended over several months so both hypotheses could be evaluated. This included compositional/metabolic assessment of the supplement, review of pharmacokinetic pathways from DHEA and pregnenolone, comparison of carnivorous versus herbivorous models, and literature review on endogenous formestane production. Importantly, the Official Laboratory provided continuous cooperation, hosting technical meetings to review data, while other national regulatory entities agreed to participate in interviews. The theory of an endogenous source was unlikely due to the gender of the horse and the estimated concentration of formestane detected in the sample. Additionally, the comparison between herbivore equine models and human omnivore/carnivore models was not applicable, as dietary sources markedly influence carbon isotope ratios (δ13C), making IRMS interpretations unreliable. Paula Soza-Ossandón1, 2, Adam Cawley3, David Batty3, Terence See Ming WAN4 Detection of Formestane, 4-Hydroxytestosterone, and 6α-Hydroxyandrostenedione in a Female Thoroughbred Racehorse in Chile: Analytical Findings, Origin Hypotheses, and Regulatory Collaboration
RkJQdWJsaXNoZXIy MTI3ODI1