A comparison between methadone and buprenorphine for perioperative analgesia in dogs undergoing ovariohysterectomy

ObjectiveTo investigate whether preoperative methadone provides superior perioperative analgesia compared to buprenorphine in dogs undergoing ovariohysterectomy. MethodsEighty female dogs were recruited to an assessor-blinded, randomised, clinical trial. Dogs received a premedication dose of 0<bold></bold>05mg/kg acepromazine or 10g/kg medetomidine combined with either 0<bold></bold>3mg/kg methadone or 20g/kg buprenorphine intramuscularly. Anaesthesia was induced with propofol and maintained with isoflurane. Pain was assessed using two scoring schemes (a dynamic interactive visual analogue scale and the short form of the Glasgow Composite Pain Scale) before premedication, 30minutes later and every hour for 8hours after premedication. If indicated, rescue analgesia was provided with methadone. Meloxicam was administered after the final assessment. The area under the curve for change in pain scores over time and the requirement for rescue analgesia were compared between groups. ResultsGroups premedicated with buprenorphine had significantly higher pain scores than those premedicated with methadone. There was no interaction between opioid and sedative for any outcome measure. Rescue analgesia was required by significantly more dogs premedicated with buprenorphine (45%) than that of methadone (20%). Clinical SignificanceAt the doses investigated, methadone produced superior postoperative analgesia compared to buprenorphine in dogs undergoing ovariohysterectomy.