Methadone-fluconazole formulations provide superior clinical efficacy compared to buprenorphine injection in dogs...

To determine the perioperative efficacy and safety of methadone-fluconazole injection followed by oral methadone-fluconazole-naltrexone (methadone-fluconazole) compared to IM buprenorphine followed by oral codeine (buprenorphine).

Healthy dogs undergoing elective ovariohysterectomy or castration from October 2019 through December 2019 were blocked to treatment by week. The methadone-fluconazole group treatment included methadone-fluconazole (0.5 and 2.5 mg/kg, SC) preoperatively and once postoperatively; methadone-fluconazole-naltrexone (0.5, 2.5, and 0.125 mg/kg, PO, q 12 h) and an NSAID started approximately 24 hours after surgery. The buprenorphine group included buprenorphine preoperatively (0.02 mg/kg, IM) and postoperatively (0.01 mg/kg, IM), and then codeine (1 to 2 mg/kg, PO, q 8 h) and an NSAID started approximately 8 hours postoperatively. Preoperative sedation included acepromazine; anesthetic induction included ketamine-midazolam and isoflurane anesthesia. Faculty-supervised veterinary students performed the anesthesia and surgery. The Glasgow Composite Measure Pain Scale assessed postoperative pain; treatment failures included total pain scores > 5 (if nonmobile), > 6 (if mobile), and need for additional analgesia/sedation. Variables of interest were compared between groups.

Enrollment included 119 dogs in the methadone-fluconaze group (47 male, 72 female) and 120 dogs in the buprenorphine group (44 male, 76 female). One dog was excluded (methadone-fluconazole) due to requiring additional surgery. Propofol was needed for anesthetic induction in 2 methadone-fluconazole and 8 buprenorphine dogs. Ephedrine was administered for intraoperative hypotension to 4 of 119 (methadone-fluconazole) and 8 of 120 (buprenorphine) dogs. One dog (methadone) received atropine. Mean ± SD postoperative rectal temperatures were significantly lower in methadone-fluconazole (35.6 ± 1.1 °C) than buprenorphine (36.1 ± 1.0 °C) dogs. Significantly more treatment failures occurred from buprenorphine (8 of 120) than methadone-fluconazole (1 of 119).

Methadone-fluconazole formulations provided superior clinical efficacy compared to buprenorphine.

Methadone-fluconazole formulations provide effective analgesia with twice-daily administration.