Behavioral and cardiorespiratory effects of a medetomidine and tramadol combination in horses

Importance: The use of combinations of sedative and analgesic drugs during standing procedures in horses is necessary to provide reliable sedation with minimal ataxia and reduced responses to surgical or other stimuli in horses.Objective: This study assessed the behavioral and cardiorespiratory effects of medetomidine (M) administered with and without tramadol (T) in horses.Methods: Eight horses were sedated intravenously with M (5 µg/kg) alone or with T (2 mg/kg) in arandomized, blind, two-way crossover trial.Behavioral responses, including head height above the ground (HHAG), postural instability (PI), and response to pressure stimulus (RPS), and cardiorespiratory responses, including vital variables and blood analyses, were assessed following administration.Results: There were no clinical meaningful differences in cardiorespiratory values, HHAG, or PI between the groups.The RPS score over the scapula was significantly higher in the medetomidine and tramadol (MT) group (p < 0.05) and a trend towards a higher RPS score over the femur was observed (p = 0.08) in the MT group.Heart rate decreased significantly below baseline from 10 to 40 minutes in both treatments.Conclusions and Relevance: These results suggest that the MT combination may provide sufficient sedation and analgesia with minimal cardiorespiratory changes in horses.