Sedative and mechanical antinociceptive effects of four dosages of romifidine administered intravenously to donkeys

•Information about sedation and analgesia with romifidine in donkeys is scarce.•Sedation scores (SS) and head heights above ground (HHAG) were used to assess sedation.•Mechanical nociceptive thresholds (MNT) were used to assess analgesia.•Romifidine (40-100 μg/kg IV) increased SS and MNT, and reduced HHAG.•Romifidine induced both sedation and analgesia; only analgesia was dose-dependent.

Although romifidine is commonly used to provide sedation and analgesia for the facilitation of clinical procedures in donkeys, limited scientific information is available for this drug in this species. This randomized, controlled, crossover, Latin-square, blinded study compared the sedative and antinociceptive effects of four dosages of romifidine (40, 60, 80, and 100 μg/kg IV; R40, R60, R80, and R100, respectively), acepromazine (0.1 mg/kg IV; ACE) and saline (0.9%, 5 mL IV) by assigning sedation scores (SS) and measuring head heights above ground (HHAG) and mechanical nociceptive thresholds (MNT) in donkeys. Areas under the curve (AUC) from 0 to 30, 30-60, 60-120, and 120-180 min after administration were computed for SS, HHAG, and MNT and compared among treatments. Romifidine and ACE, but not saline, induced clinical signs of sedation. SS-AUC0-30 for R60, R80 and R100, and SS-AUC30-60 for R100 were higher than corresponding values for saline. HHAG-AUC30-60 for R40 and R80, and HHAG-AUC60-120 for R40, R60, R80 and R100 were smaller than for saline. HHAG-AUC60-120 for R100 were also smaller than those for ACE. Romifidine, but not saline or ACE, increased MNT. MNT-AUC0-30 and MNT-AUC30-60 for R40, R60, R80 and R100, and MNT-AUC60-120 for R80 and R100 were higher than corresponding values for saline and ACE. MNT-AUC60-120 for R100 were higher than for all other romifidine treatments. In donkeys, the degree of sedation was similar for the four dosages of romifidine, but antinociception was dose-dependent.