A comparative study of xylazine-induced mechanical hypoalgesia in donkeys and horses.

摘要

Objective: To compare the effects of xylazine on mechanical nociceptive thresholds in donkeys and horses. Study design: Randomized, controlled, crossover, Latin-square, operator-blinded design. Animals: Six 3.1+or-0.89 year old standard donkeys weighing 145.0+or-30.5 kg and six 9.6+or-4.4 year old Thoroughbred horses weighing 456.0+or-69.0 kg. Methods: Each animal received one of four doses of xylazine (0.5, 0.7, 0.9, and 1.1 mg kg-1), or acepromazine (0.05 mg kg-1) or saline solution (0.9%) intravenously and mechanical nociceptive thresholds were assessed over 90 minutes. The areas under the threshold change versus time curve values for 60 minutes (AUC_0-60) post-drug administration were used to compare the effect of treatment. A 1-week interval was allowed between successive trials on each animal. Results: All doses of xylazine, but not acepromazine or saline, increased mechanical thresholds for up to 60 minutes. Xylazine-induced hypoalgesia was dose-dependent and corresponding AUC_0-60 values for each treatment were not significantly different between donkeys and horses (p>=0.0697). Conclusion: The hypoalgesic effects of xylazine at four different doses were not different between donkeys and horses. Clinical relevance: Xylazine induced a similar degree of mechanical hypoalgesia in donkeys and horses suggesting that similar doses are needed for both species with regard to analgesia.