Cagnardi P, Villa R, Ravasio G, Lucatello L, Di Cesare F, Capolongo F, Boccardo A, Pravettoni D
a Department of Health, Animal Science and Food Safety , Università degli Studi di Milano , Milan 20133 , Italy.
b Department of Veterinary Medicine , Università degli Studi di Milano , Milan 20133 , Italy.
N Z Vet J. 2017 Jan;65(1):14-18. doi: 10.1080/00480169.2016.1237313. Epub 2016 Oct 12.
To evaluate the pharmacokinetics of dexmedetomidine (DEX) administered I/V at a dose of 5 µg/kg bodyweight in dairy calves and to compare the sedative effects of anaesthetic protocols involving DEX and xylazine.
Nine dairy calves, aged 17-20 days, were treated with 5 µg/kg I/V dexmedetomidine. For pharmacokinetic evaluation, blood samples were collected over 12 hours and serum samples were analysed by high performance liquid chromatography-mass spectrometry. Another nine dairy calves, aged 16-20 days, were treated with 0.2 mg/kg I/V xylazine. After both treatments, heart rate, respiratory rate and rectal temperature were measured for 20 minutes. Sedation quality and recovery times were also assessed.
The kinetics of DEX was best described by a two-compartment model. The distribution and elimination half-lives were 8.7 (SD 5.0) and 83.5 (SD 67.5) minutes, respectively. Mean maximum concentration and body clearance were 12.5 (SD 8.6) ng/mL and 27.9 (SD 13.1) mL/minute/kg, respectively; the mean volume of distribution at steady state was 2,170.8 (SD 1,657.5) mL/kg. A decrease in heart rate was observed after treatments with both DEX and xylazine. No differences in heart or respiration rate, or rectal temperature were observed between the two treatment groups. The onset of sedation occurred after 2.7 (SD 0.67) minutes for calves treated with DEX and 2.8 (SD 0.78) minutes for calves treated with xylazine, and was characterised by a similar degree of deep sedation and ease of handling of the calves. All recoveries were eventless, and no adverse reactions were noted.
Dexmedetomidine treatment resulted in a reliable and long lasting sedation in calves, a transient decrease in heart rate and no modification in respiratory rate or rectal temperature. The results were comparable to xylazine, the most popular alpha-2-agonist among bovine practitioners. The use of DEX in dairy calves for rapid procedures such as dehorning or castration could be suggested.
评估以5μg/kg体重静脉注射右美托咪定（DEX）在犊牛中的药代动力学，并比较包含DEX和赛拉嗪的麻醉方案的镇静效果。
对9头17 - 20日龄的犊牛静脉注射5μg/kg的右美托咪定。为进行药代动力学评估，在12小时内采集血样，血清样本通过高效液相色谱 - 质谱法进行分析。另外9头16 - 20日龄的犊牛静脉注射0.2mg/kg的赛拉嗪。两种处理后，测量心率、呼吸频率和直肠温度20分钟。还评估了镇静质量和恢复时间。
DEX的动力学最好用二室模型描述。分布半衰期和消除半衰期分别为8.7（标准差5.0）分钟和83.5（标准差67.5）分钟。平均最大浓度和全身清除率分别为12.5（标准差8.6）ng/mL和27.9（标准差13.1）mL/分钟/千克；稳态时的平均分布容积为2170.8（标准差1657.5）mL/千克。DEX和赛拉嗪处理后均观察到心率下降。两个处理组之间在心率、呼吸频率或直肠温度方面未观察到差异。接受DEX处理的犊牛在2.7（标准差0.67）分钟后出现镇静，接受赛拉嗪处理的犊牛在2.8（标准差0.78）分钟后出现镇静，其特征是犊牛的深度镇静程度相似且易于处理。所有恢复过程均顺利，未观察到不良反应。
右美托咪定处理在犊牛中产生了可靠且持久的镇静效果，心率短暂下降，呼吸频率或直肠温度无变化。结果与赛拉嗪相当，赛拉嗪是牛从业者中最常用的α-2激动剂。可建议在犊牛中使用DEX进行诸如去角或阉割等快速操作。
