Evaluation of the analgesic effects of phenylbutazone administered at a high or low dosage in horses with chronic lameness.
OBJECTIVE
To compare analgesic effects of phenylbutazone administered at a dosage of 4.4 mg/kg/d (2 mg/lb/d) or 8.8 mg/kg/d (4 mg/lb/d) in horses with chronic lameness.


METHODS
Controlled crossover study. Animals-9 horses with chronic forelimb lameness.


METHODS
Horses were treated i.v. with phenylbutazone (4.4 mg/kg/d or 8.8 mg/kg/d) or saline (0.9% NaCl) solution once daily for 4 days. All horses received all 3 treatments with a minimum of 14 days between treatments. Mean peak vertical force (mPVF) was measured and clinical lameness scores were assigned before initiation of each treatment and 6, 12, and 24 hours after the final dose for each treatment.


RESULTS
Compared with values obtained after administration of saline solution, mPVF was significantly increased at all posttreatment evaluation times when phenylbutazone was administered. Clinical lameness scores were significantly decreased 6 and 12 hours after administration of the final dose when phenylbutazone was administered at the low or high dosage but were significantly decreased 24 hours after treatment only when phenylbutazone was administered at the high dosage. No significant differences in mPVF and clinical lameness scores were found at any time when phenylbutazone was administered at the low versus high dosage.


CONCLUSIONS
Results suggest that the high dosage of phenylbutazone was not associated with greater analgesic effects, in terms of mPVF or lameness score, than was the low dosage. Considering that toxicity of phenylbutazone is related to dosage, the higher dosage may not be beneficial in chronically lame horses.
Hu
Helen H
HH
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Oklahoma State University, Stillwater, OK 74078, USA.
MacAllister
Charles G
CG
Payton
Mark E
ME
Erkert
Ronald S
RS
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000627:therapeutic use*; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D005260:Female; D006734:Horse Diseases / Q000188:drug therapy*; D006736:Horses; D007794:Lameness, Animal / Q000188:drug therapy*; D008297:Male; D010653:Phenylbutazone / Q000627:therapeutic use*; D016896:Treatment Outcome
D000894:Anti-Inflammatory Agents, Non-Steroidal; D010653:Phenylbutazone