Effect of acepromazine, butorphanol, or N-butylscopolammonium bromide on visceral and somatic nociception and duodenal motility in conscious horses.
OBJECTIVE
To evaluate effects of butorphanol, acepromazine, and N-butylscopolammonium bromide (NBB) on visceral and somatic nociception and duodenal motility in conscious, healthy horses.


METHODS
6 adult horses.


METHODS
Visceral nociception was evaluated by use of colorectal distention (CRD) and duodenal distention (DD) threshold. Somatic nociception was evaluated via thermal threshold (TT). Nose-to-ground height, heart rate, and respiratory rate were also measured. Each horse received each treatment in randomized order; investigators were not aware of treatments. Butorphanol was administered IV as a bolus (18 microg/kg) followed by constant rate infusion at 13 microg/kg/h for 2 hours, whereas acepromazine (0.04 mg/kg), NBB (0.3 mg/kg), and saline (0.9% NaCl) solution (2 mL) were administered IV as a bolus followed by constant rate infusion with saline solution (10 mL/h) for 2 hours. Variables were measured before and for 3 hours after treatment. Data were analyzed by use of a 3-factor ANOVA followed by a Bonferroni t test for multiple comparisons.


RESULTS
Nose-to-ground height decreased after acepromazine. Respiratory rate decreased after acepromazine and increased after butorphanol. Heart rate increased briefly after NBB. Some horses had an increase in TT after butorphanol and acepromazine, but there was not a significant treatment effect over time. Drug effect on DD or motility was not evident. The CRD threshold increased significantly at 5, 65, 155, and 185 minutes after acepromazine and from 5 to 65 minutes after NBB.


CONCLUSIONS
Each drug caused predictable changes in sedation and vital signs, but consistent anti-nociceptive effects were not evident.
Sanchez
L Chris
LC
Island Whirl Equine Colic Research Laboratory, Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610, USA.
Elfenbein
Johanna R
JR
Robertson
Sheilah A
SA
D000075:Acepromazine / Q000494:pharmacology*; D000818:Animals; D001831:Body Temperature / Q000187:drug effects; D002077:Butorphanol / Q000494:pharmacology*; D002086:Butylscopolammonium Bromide / Q000494:pharmacology*; D004386:Duodenum / Q000187:drug effects* / Q000502:physiology; D005260:Female; D005769:Gastrointestinal Motility / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D006736:Horses / Q000502:physiology*; D008297:Male; D018727:Muscarinic Antagonists / Q000494:pharmacology*; D010147:Pain Measurement / Q000187:drug effects* / Q000379:methods / Q000662:veterinary; D011897:Random Allocation; D012119:Respiration / Q000187:drug effects
D018727:Muscarinic Antagonists; D002086:Butylscopolammonium Bromide; D000075:Acepromazine; D002077:Butorphanol