Pharmacokinetic Characterization of Xylazine in Goats with Simultaneous Anesthesia Studies

The aim was to study the pharmacokinetics of xylazine as a stable anesthetic in goats.In this study,goats were injected with xylazine at the rate of 0.3 mL·kg^-1 intramusculally,and blood samples were collected at 1,3,5,10,20,30,45,60,90,120,180,and 240 min after administration,respectively.Xylazine was extracted by liquid-liquid extraction and separation method,and blood concentration was determined by high performance liquid chromatography （HPLC）.The pharmacokinetic characteristics of xylazine in healthy goats were analyzed by pharmacokinetic software.The results showed that the chromatographic peak time of xylazine chromatography was 9-11 min.The specificity of the method was good.The linear correlation coefficient R~2 of the standard curve was 0.9982 when the concentration of xylazine was in the range of 10^-1×1 000 ng.The pharmacokinetic model of xylazine in goats was a one-chamber model with first-order rate absorption,distribution half-life t_1/2Ka was （0.49±0.041） min,elimination half-life t_1/2Ke was （23.3±2.5） min,and the peak time （T_p） of the highest concentration was （2.8±0.2） min.The total drug clearance CL/F was（0.00016±0.000016） mg·kg^-1·min^-1 (ng·mL^-1),and the minimum effective blood concentration was 56.6 ng·mL^-1,which was consistent with the clinical anesthetic effect.The results showed that xylazine had the characteristics of rapid absorption,wide distribution,short peak time,slow clearance rate,and long anesthetic time in goats,which could be used as the basic drug for the development of goat complex anesthetic preparation.