A comparison of detomidine in combination with saline, morphine or methadone in horses submitted to experimental oral stimuli

This study aimed to compare the sedative and cardiopulmonary effects of detomidine in combination with saline, morphine or methadone and to determine whether the addition of these opioids increases the degree of sedation in horses submitted to experimental oral stimuli. In a blinded, randomized, experimental study, six adult mares were evaluated using a crossover design with at least 15 days between trials: 10μg/kg detomidine in combination with saline (D/SAL), 0.1mg/kg morphine (D/ MORPH) or 0.1mg/kg methadone (D/METH). The degree of sedation, response to oral stimuli and cardiopulmonary parameters were monitored for 120 minutes. Parametric data were analyzed using the ANOVA and Tukey's tests, and non- parametric data were analyzed with the Kruskal-Wallis and Friedman's tests with the post-Dunn test (P<0.05). The degree of sedation was significantly greater for the D/SAL than for the D/MORPH and D/METH treatments at 30 min. The horses' responses to the oral stimuli decreased significantly following all treatments at 5 and 30 min from baseline values. The heart rate, respiratory rate, arterial pH and blood gas variables were all similar among the treatment groups. Mean arterial blood pressure was significantly higher in the D/MORPH group when compared with the D/SAL group between 75 and 120 min. It was concluded that all treatments provided sedative effects with mild cardiopulmonary changes. However the addition of morphine or methadone to detomidine did not improve the degree of sedation in horses submitted to experimental oral stimuli.