Xylazine is widely used worldwide as a short-acting sedative in general equine and racing practice. In the UK, although it has a legitimate use during training, equine anti-doping rules state it is a prohibited substance on race day. The aim of the study was to produce a detection time (DT) to better inform European veterinary surgeons so that xylazine can be used appropriately under regulatory rules. Previous publications have various limitations pertaining to analysis method, particularly for plasma and limited length of time of sample collection. In this study, pharmacokinetic data were produced for xylazine and 4-OH-xylazine in equine urine and plasma following a single intravenous xylazine dose of 0.4 mg/kg to six Thoroughbred horses. Pharmacokinetic parameters were generated from a 3-compartmental model with clearance = 15.8 ± 4.88 ml min-1 kg-1 , Vss = 1.44 ± 0.38 L/kg, terminal half-life = 29.8 ± 12.7 hr and a DT determined at 71 hr for the administration of xylazine (Chanazine® ) in plasma and urine. Urine screening should aim to detect the 4-OH-xylazine metabolite, which can act as an indicator for the xylazine plasma concentration. A DT of 72 hr has been agreed by the European Horserace Scientific Liaison Committee, to be implemented in June 2019.

中文翻译：

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重新评估赛灵嗪对纯种马的药代动力学。

赛拉嗪在全球范围内被广泛用作马术和赛马中的短效镇静剂。在英国，尽管在训练中可以合法使用，但马防兴奋剂规则指出在比赛当天它是一种禁用物质。该研究的目的是产生检测时间（DT），以便更好地为欧洲兽医提供信息，以便可以根据法规规则适当使用甲苯噻嗪。先前的出版物具有与分析方法有关的各种限制，特别是对于血浆和有限的样品采集时间长度。在这项研究中，对六匹纯种马单次静脉注射甲苯噻嗪0.4 mg / kg的剂量后，在马尿和血浆中产生了甲苯噻嗪和4-OH-甲苯噻嗪的药代动力学数据。药代动力学参数由清除率= 15.8±4的3室模型产生。88 ml min-1 kg-1，Vss = 1.44±0.38 L / kg，终末半衰期= 29.8±12.7 hr，在血浆和尿液中使用甲苯噻嗪（Chanazine®）的DT在71 hr时确定。尿液筛查应旨在检测4-OH-甲苯噻嗪代谢产物，该代谢产物可作为甲苯噻嗪血浆浓度的指标。欧洲赛马科学联络委员会已同意将DT设为72小时，并将于2019年6月实施。