Analgesic effects of butorphanol tartrate and phenylbutazone administered alone and in combination in young horses undergoing routine castration.
OBJECTIVE
To compare the analgesic efficacy of administration of butorphanol tartrate, phenylbutazone, or both drugs in combination in colts undergoing routine castration.


METHODS
Randomized controlled clinical trial.


METHODS
36 client-owned colts.


METHODS
Horses received treatment with butorphanol alone (0.05 mg/kg [0.023 mg/lb], IM, prior to surgery and then q 4 h for 24 hours), phenylbutazone alone (4.4 mg/kg [2.0 mg/lb], IV, prior to surgery and then 2.2 mg/kg [1.0 mg/lb], PO, q 12 h for 3 days), or butorphanol and phenylbutazone at the aforementioned dosages (12 horses/group). For single-drug-treated horses, appropriate placebos were administered to balance treatment protocols among groups. All horses were anesthetized, and lidocaine hydrochloride was injected into each testis. Physical and physiological variables, plasma cortisol concentration, body weight, and water consumption were assessed before and at intervals after surgery, and induction of and recovery from anesthesia were subjectively characterized. Observers assessed signs of pain by use of a visual analogue scale and a numerical rating scale.


RESULTS
Significant changes in gastrointestinal sounds, fecal output, and plasma cortisol concentrations were evident in each treatment group over time, compared with preoperative values. At any time point, assessed variables and signs of pain did not differ significantly among groups, although the duration of recumbency after surgery was longest for the butorphanol-phenylbutazone-treated horses.


CONCLUSIONS
With intratesticular injections of lidocaine, administration of butorphanol to anesthetized young horses undergoing routine castration had the same apparent analgesic effect as phenylbutazone treatment. Combined butorphanolphenylbutazone treatment was not apparently superior to either drug used alone.
Sanz
Macarena G
MG
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman, WA 99164, USA.
Sellon
Debra C
DC
Cary
Julie A
JA
Hines
Melissa T
MT
Farnsworth
Kelly D
KD
D000700:Analgesics / Q000008:administration & dosage / Q000627:therapeutic use; D000818:Animals; D002077:Butorphanol / Q000008:administration & dosage / Q000627:therapeutic use*; D004359:Drug Therapy, Combination / Q000662:veterinary; D006736:Horses / Q000601:surgery*; D008297:Male; D009919:Orchiectomy / Q000379:methods / Q000662:veterinary*; D010149:Postoperative Pain / Q000188:drug therapy / Q000662:veterinary*; D010653:Phenylbutazone / Q000008:administration & dosage / Q000627:therapeutic use*; D013997:Time Factors
D000700:Analgesics; D010653:Phenylbutazone; D002077:Butorphanol