Comparison of the analgesic properties of transdermally administered fentanyl and intramuscularly administered buprenorphine during and following experimental orthopedic surgery in sheep

Objective-To evaluate the analgesic properties of transdermally administered fentanyl and IM administered buprenorphine in sheep undergoing unilateral tibial osteotomy. Animals-20 mature sheep. Procedures-Fentanyl patches (n = 15 sheep) or placebo patches (5 sheep) were applied 12 hours before sheep underwent general anesthesia and a unilateral tibial osteotomy. Buprenorphine was administered to the placebo group every 6 hours commencing at time of induction. Signs of pain were assessed every 12 hours after surgery by 2 independent observers unaware of treatment groups. Results-There were no differences in preoperative and intraoperative physiologic data between the 2 groups. Sheep treated with fentanyl required less preoperative administration of diazepam for sedation and had significantly lower postoperative pain scores, compared with those treated with buprenorphine. No complications associated with the antebrachium at the site of patch application were detected. Conclusions and Clinical Relevance-Under the conditions of this study, transdermally administered fentanyl was a superior option to IM administered buprenorphine for alleviation of postoperative orthopedic pain in sheep. This information can be used to assist clinicians in the development of a rational analgesic regimen for research and clinical patients. (Am J Vet Res'2009;70:418-422)