Comparison of the postoperative analgesic effects of buprenorphine and piritramide following experimental orthopaedic surgery in sheep

Introduction: Long-acting opioids may be needed for postoperative pain relief in sheep. Reports on the analgesic efficacy of the partial Ci agonist buprenorphine, however, are controversial. Therefore, the aim of this study was to compare the effects of buprenorphine with the mu full agonist piritramide on clinical pain following orthopaedic surgery in sheep. Material and methods: Postoperative analgesia of intramuscular buprenorphine (0.01 mg/kg) and piritramide (0.57 mg/kg) were evaluated in a prospective, randomised and blinded study in 22 ewes submitted to an experimental tibia osteotomy. For evaluation of postoperative analgesia the rime from extubation to first attempt to stand, to standing, to first food/water uptake, to first postoperative analgesic treatment, the number of animals treated per group, postoperative behaviour and lameness scores were compared. Results: The distribution of behavioural scores in standing/walking animals was significantly different (P = 0.018) between the two treatment groups. In the buprenorphine group behaviour scores ranged more in the lower score range while higher scores were recorded in the piritramide group. In both groups the same number of nine sheep required additional postoperative analgesic treatment at almost identical time intervals. No significant differences existed for the other variables. Conclusion: Buprenorphine and piritramide provided effective analgesia following tibia osteotomy in sheep with a slightly better quality in animals pre-treated with buprenorphine.