Methandienone is an anabolic-androgenic steroid that is prohibited in equine sports due to its potential performance enhancing properties. Metabolism and detection of methandienone in equine urine have been investigated comprehensively in literature; however, there is a limited knowledge about its metabolites in equine plasma and no information about its detection in equine hair. Following a multi-dose oral administration of methandienone to two Thoroughbred horses, 17-epimethandienone, methyltestosterone, two mono-hydroxylated, two di-hydroxylated and three 17α-methylandrostanetriol metabolites were detected in plasma. The majority of these were present as free analytes, whilst the mono-hydroxylated metabolites and one isomer of 17α-methylandrostanetriol were partially conjugated. Estimated peak concentrations of methandienone were 6,000 and 11,100 pg/ml; meanwhile, they were 25.4 and 40.5 pg/ml for methyltestosterone. The most abundant analyte in the post-administration plasma samples of both horses was the mono-hydroxylated metabolite; however, the parent compound provided the longest detection (up to 96 h). Screening analysis of hair enabled the detection of methandienone in mane hair samples only, for up to 3 months. Its mono- and di-hydroxylated metabolites were detected with greater peak responses for up to 6 months post-administration in both mane and tail samples, showing that these metabolites could be better analytical targets for hair analysis when administered orally. A follow-up methodology with an extensive wash procedure confirmed the presence of methandienone and its metabolites in a number of post-administration hair samples. Final wash samples were also analysed to assess the degree of internal incorporation (via bloodstream) against possible external deposition (via sweat/sebum).

中文翻译：

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多剂量口服后马尿、血浆和毛发中大力二酮及其代谢物的检测

大力补是一种合成代谢雄激素类固醇，由于其潜在的性能增强特性，在马术运动中被禁止使用。文献对马尿中大力二酮的代谢和检测进行了全面的研究；然而，对其在马血浆中的代谢物的了解有限，也没有关于其在马毛发中检测的信息。两匹纯种马口服多剂量大力雄酮后，血浆中检测到 17-表雄二酮、甲基睾酮、两种单羟基化、两种二羟基化和三种 17α-甲基雄甾三醇代谢物。其中大部分以游离分析物的形式存在，而单羟基化代谢物和 17α-甲基雄甾烷三醇的一种异构体则部分结合。估计的大力二酮峰值浓度为 6,000 和 11,100 pg/ml；与此同时，甲基睾酮含量分别为 25.4 pg/ml 和 40.5 pg/ml。两匹马给药后血浆样本中最丰富的分析物是单羟基化代谢物；然而，母体化合物提供了最长的检测（长达 96 小时）。对头发进行筛选分析，仅在鬃毛样本中检测出大力补，持续时间长达 3 个月。在鬃毛和尾部样本中，在给药后长达 6 个月内检测到其单羟基化和二羟基化代谢物具有更高的峰值响应，这表明这些代谢物在口服给药时可以成为毛发分析的更好的分析目标。采用广泛清洗程序的后续方法证实了许多给药后头发样本中存在大力二酮及其代谢物。还分析了最终的洗涤样品，以评估内部结合程度（通过血流）与可能的外部沉积（通过汗液/皮脂）的程度。