Effects of acepromazine, butorphanol and buprenorphine on thermal and mechanical nociceptive thresholds in horses.
Authors: Love E J, Taylor P M, Murrell J, Whay H R
Journal: Equine veterinary journal
Summary
# Editorial Summary Love et al. (2012) set out to evaluate buprenorphine as an analgesic agent in horses, comparing its antinociceptive effects against butorphanol and control treatments when combined with acepromazine. Using a blinded, crossover design with six Thoroughbred geldings, researchers measured thermal and mechanical nociceptive thresholds following intravenous administration of three buprenorphine doses (5, 7.5, and 10 µg/kg) alongside acepromazine 0.05 mg/kg, with measurements continuing for up to 24 hours post-treatment. Thermal antinociception duration increased dose-dependently: buprenorphine 5 µg/kg produced 7.4 hours of analgesia, rising to 9.4 hours at 10 µg/kg, substantially outlasting butorphanol's 2.9-hour effect and matching or exceeding clinical requirements for perioperative pain management. No serious adverse effects were documented, though the assessment protocol revealed locomotor stimulation that interfered with mechanical threshold measurement—a finding worth considering in clinical applications. These results suggest buprenorphine merits further investigation as a viable analgesic for equine practice, particularly for procedures requiring sustained pain relief without the short duration limitations of traditional opioid protocols.
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Practical Takeaways
- •Buprenorphine combined with acepromazine offers significantly longer pain relief (7–9 hours) than butorphanol in horses, making it potentially valuable for post-operative or acute pain management in clinical settings
- •The antinociceptive effect appears dose-responsive within the 5–10 µg/kg range, allowing practitioners to tailor analgesia duration to specific clinical needs
- •Further clinical validation studies are needed before routine adoption, but buprenorphine warrants consideration as an alternative opioid for equine pain management protocols
Key Findings
- •Buprenorphine at 5, 7.5, and 10 µg/kg produced thermal antinociception lasting 7.4–9.4 hours when combined with acepromazine, significantly longer than butorphanol (2.9 h) or glucose control (0.5 h)
- •Duration of thermal antinociception increased dose-dependently with buprenorphine: 5 µg/kg (7.4 h), 7.5 µg/kg (7.8 h), and 10 µg/kg (9.4 h)
- •No serious adverse effects were reported with any buprenorphine dose, though mechanical threshold assessment was confounded by locomotor stimulation from acepromazine
- •Buprenorphine demonstrated superior and more sustained analgesic efficacy compared to the commonly used opioid butorphanol in horses