The analgesic effects of intrathecal xylazine and detomidine in sheep and their antagonism with systemic atipamezole.
OBJECTIVE
To evaluate the analgesic and adverse side effects of intrathecal (IT) xylazine (XYL) and detomidine (DET) and the subsequent effects of two doses of intravenous (IV) atipamezole (ATI).


METHODS
Prospective, randomized, cross-over.


METHODS
Five adult healthy female sheep with mean body mass of 55 +/- 2.3 kg. Material and methods Each sheep underwent four treatments: 1) 50 microg kg(-1) XYL IT and 5 microg kg(-1) ATI IV, 2) 50 microg kg(-1) XYL IT and 2.5 microg kg(-1) ATI IV, 3) 10 microg kg(-1) DET IT and 5 microg kg(-1) ATI IV, 4) 10 microg kg(-1) DET IT and 2.5 microg kg(-1) ATI IV. Pain threshold (TH) was tested by applying pulsed and stepwise incremental direct current to the skin overlying the pastern. The current at the point of foot lift was recorded as the TH. Heart rate (HR), mean arterial pressure, arterial oxygen (PO(2)) and carbon dioxide (PCO(2)) tensions were monitored. Outcomes were derived as differences between baseline assessment and measurements after treatment. Two-way anova was used to analyse drug effects, treatment differences between groups were examined with an F-test or Wilcoxon's rank sum test in case of non-parametric data distribution. p was set at 0.05.


RESULTS
Both drugs increased the pain TH, caused small increases in PCO(2), and small decreases in HR, the latter was only significant for XYL recipients. Xylazine produced a significantly higher TH, more rapidly and for longer than DET. Atipamezole only significantly affected PaCO(2) in the XYL group 2. The pain TH was not affected in either group after IV ATI.


CONCLUSIONS
At the doses used, IT XYL, and to a lesser extent DET, induced pastern analgesia. Atipamezole 5 microg kg(-1) IV antagonized some side effects without affecting analgesia.


CONCLUSIONS
Intrathecal XYL may be useful as an analgesic in sheep. Its safety is increased because IV ATI antagonizes side effects, but not analgesia.
Christina Haerdi-Landerer
M
M
AO Research Institute, Davos, Switzerland. christina.haerdi@aofoundation.org
Schlegel
Urs
U
Neiger-Aeschbacher
Gina
G
D000316:Adrenergic alpha-Agonists / Q000008:administration & dosage* / Q000009:adverse effects; D000317:Adrenergic alpha-Antagonists / Q000008:administration & dosage / Q000009:adverse effects; D000700:Analgesics / Q000008:administration & dosage* / Q000009:adverse effects / Q000037:antagonists & inhibitors; D000818:Animals; D000830:Animals, Laboratory / Q000502:physiology*; D018592:Cross-Over Studies; D005260:Female; D006439:Hemodynamics; D007093:Imidazoles / Q000008:administration & dosage / Q000009:adverse effects / Q000037:antagonists & inhibitors; D011446:Prospective Studies; D012756:Sheep / Q000502:physiology*; D016896:Treatment Outcome; D014991:Xylazine / Q000008:administration & dosage / Q000009:adverse effects / Q000037:antagonists & inhibitors
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D000700:Analgesics; D007093:Imidazoles; C050701:atipamezole; D014991:Xylazine; C041255:detomidine