title: A comparative study of xylazine-induced mechanical hypoalgesia in donkeys and horses.
abstract: OBJECTIVE
  To compare the effects of xylazine on mechanical nociceptive thresholds in donkeys and horses.
  
  
  METHODS
  Randomized, controlled, crossover, Latin-square, operator-blinded design.
  
  
  METHODS
  Six 3.1 ± 0.89 year old standard donkeys weighing 145.0 ± 30.5 kg and six 9.6 ± 4.4 year old Thoroughbred horses weighing 456.0 ± 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).
  
  
  CONCLUSIONS
  The hypoalgesic effects of xylazine at four different doses were not different between donkeys and horses.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Pathobiology, Ross University School of Veterinary Medicine, Basseterre, St. Kitts, West Indies. ilizarraga@rossvet.edu.kn
authors.forename: Ignacio
authors.initials: I
authors.lastname: Lizarraga
authors.forename: Thierry
authors.initials: T
authors.lastname: Beths
mesh_terms: D000075:Acepromazine / Q000493:pharmacokinetics / Q000494:pharmacology; D000700:Analgesics / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D000818:Animals; D019540:Area Under Curve; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D018397:Equidae; D005260:Female; D008297:Male; D010146:Pain / Q000517:prevention & control / Q000662:veterinary*; D014991:Xylazine / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*
chemical_list: D000700:Analgesics; D014991:Xylazine; D000075:Acepromazine