Ovariohysterectomy in dogs: does methadone premedication give better postoperative pain control than buprenorphine? — LIKELY

LIKELY: In female dogs undergoing ovariohysterectomy, methadone premedication gave better postoperative analgesia than buprenorphine in the single head-to-head randomised trial. In Shah 2018 (assessor-blinded, randomised clinical trial, 80 female dogs), dogs premedicated with methadone 0.3 mg/kg intramuscularly had significantly lower pain scores over 8 hours than dogs premedicated with buprenorphine 20 micrograms/kg intramuscularly (area under the curve for change in pain scores, on both a dynamic interactive visual analogue scale and the short form of the Glasgow Composite Pain Scale), and rescue analgesia was required by 20% of methadone dogs versus 45% of buprenorphine dogs — an absolute difference of 25 percentage points, a 56% relative reduction in the proportion needing rescue. Design class (a): randomisation and blinding are established by the carded record — Shah 2018 states 'assessor-blinded, randomised, clinical trial' in its own wording and carries MeSH Random Allocation; the blinding established is assessor (outcome-assessor) blinding, not double-blinding, and the balance claims no more than that. The honest limits: this is one trial at one pair of doses (methadone 0.3 mg/kg vs buprenorphine 20 micrograms/kg, each combined with acepromazine or medetomidine sedation); the record gives no absolute pain-score values, only the significant between-group comparison; meloxicam was withheld until after the final assessment, so the comparison is opioid against opioid without an NSAID background; and follow-up is 8 hours only. One clear, adequately sized, assessor-blinded randomised trial with consistent results across two pain scales and rescue use supports LIKELY, not PROBABLE. Drafted Nov 10, 2026 (VetMed build, topic #521); all figures from the abstract fetched and verified at drafting.