Methadone or Butorphanol as Pre-Anaesthetic Agents Combined with Romifidine in Horses Undergoing Elective Surgery: Qualitative Assessment of Sedation and Induction.
Authors: Nannarone Sara, Giannettoni Giacomo, Laurenza Chiara, Giontella Andrea, Moretti Giulia
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Romifidine combined with an opioid remains standard pre-anaesthetic practice in equine surgery, yet evidence comparing commonly available agents remains limited. Nannarone and colleagues (2021) evaluated sedation quality and induction characteristics in 20 horses receiving either methadone or butorphanol alongside romifidine, scoring sedation depth at 10 minutes post-injection and monitoring physiological parameters throughout induction and intubation. Although horses given methadone demonstrated lower overall sedation scores (p = 0.002), this did not translate to clinically meaningful differences in induction quality or intubation time—both drugs produced good-to-excellent induction in the majority of cases, with no animals experiencing excessive ataxia or falling. The principal physiological distinction was greater bradycardia in the methadone group (p = 0.017), including a higher frequency of atrioventricular blocks, though these resolved once general anaesthesia was established. For practitioners selecting pre-anaesthetic combinations, these findings suggest both agents are suitable choices when combined with romifidine; however, the relative analgesic potency of methadone may warrant consideration in horses anticipated to require enhanced perioperative pain control, whilst those with pre-existing cardiac concerns might be managed more conservatively with butorphanol given its more moderate effects on heart rate.
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Practical Takeaways
- •Methadone can be used as an alternative to butorphanol as a pre-anesthetic with romifidine; clinical induction quality is equivalent despite appearing lighter sedation
- •Monitor for increased bradycardia and cardiac arrhythmias when using methadone pre-operatively, though these resolve once general anesthesia is induced
- •Choice between methadone and butorphanol may depend on analgesic potency requirements post-operatively rather than induction quality alone
Key Findings
- •Methadone produced lower overall sedation scores than butorphanol (p = 0.002) when combined with romifidine
- •Despite lower sedation scores with methadone, quality and timing of induction and intubation remained unchanged between groups
- •Methadone induced greater bradycardia (p = 0.017) with higher incidence of atrioventricular blocks that resolved during general anesthesia
- •Both drugs provided good-to-excellent quality of induction in most animals with no safety concerns regarding extreme ataxia or lack of sedation