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Objectives

To determine whether methadone, administered before orthopaedic surgery, results in improved postoperative analgesia compared to buprenorphine.

Methods

Thirty-eight dogs undergoing orthopaedic surgeries (the majority being tibial tuberosity advancement or elbow arthrotomy) were premedicated with 0 · 03 mg/kg acepromazine and either 20 µg/kg buprenorphine or 0 · 5 mg/kg methadone, intramuscularly, allocated randomly. Anaesthesia was induced with propofol intravenously to effect and maintained with isoflurane in oxygen. 0 · 2 mg/kg meloxicam was administered at anaesthetic induction. Sedation was assessed by means of a dynamic interactive visual analogue and simple descriptive scales and pain by dynamic interactive visual analogue and the short form Glasgow composite pain scales, by a single observer blinded to treatment group at intervals for 8 hours following premedication.

Results

Sedation scores were higher than baseline in both groups following premedication until the end of the assessment period (P = 0 · 0001), with no differences between groups. Pain scores were lower overall in dogs premedicated with methadone (dynamic interactive visual analogue scale P = 0 · 048; short form Glasgow composite pain scale P = 0 · 0045), and these dogs required less additional analgesia (42%, compared to 79% premedicated with buprenorphine, P = 0 · 045).

Clinical Significance

At the doses investigated, methadone produced superior analgesia to buprenorphine for 8 hours postoperatively in dogs undergoing orthopaedic surgery.