Two doses of subcutaneous methadone for postoperative analgesia in dogs undergoing tibial plateau levelling osteotomies.

Objectives: To evaluate analgesia, sedation and adverse effects of two doses of subcutaneous methadone in dogs undergoing tibial plateau levelling osteotomy. Materials and Methods: Seventeen client‐owned dogs undergoing unilateral tibial plateau levelling osteotomy were randomly allocated to receive either 0.25 mg/kg methadone (eight dogs) or 0.5 mg/kg methadone (nine dogs). All dogs were premedicated with methadone and 2 to 6 mcg/kg dexmedetomidine subcutaneously. They were induced and maintained on a standard protocol. All animals received a second dose of methadone subcutaneously 4 hours after premedication and a 4.4 mg/kg dose of carprofen subcutaneously at 8 hours after premedication. During surgery, blood pressure, heart rate and temperature were assessed every 5 minutes. Postoperatively, sedation scores, temperature, heart rate and Glasgow composite modified pain score – short form were assessed for 12 hours postoperatively. Results: One of 17 (5.9%) dogs had intraoperative hypotension, nine of 17 dogs had intra‐operative bradyarrhythmias and 17 of 17 dogs had intra‐operative hypothermia. No dogs required intra‐operative rescue. Composite modified pain score – short form scores were below the threshold for intervention in 16 of 17 (94.1%) animals. Only one of 17 (5.9%) dogs required rescue analgesia. Median sedation score was 0 by the T8 time point. Adverse events were rare in both groups with only vocalisation and hypothermia reported commonly postoperatively. Clinical Significance: Two doses of methadone at either 0.25 or 0.5 mg/kg administered via subcutaneous injections pre‐operatively and 4 hours later, along with 4.4 mg/kg carprofen subcutaneously 8 hours after the first methadone dose appear to provide sufficient pain control for up to 12 hours in dogs undergoing tibial plateau levelling osteotomy. [ABSTRACT FROM AUTHOR]