Cardiorespiratory and metabolic effects of xylazine, detomidine, and a combination of xylazine and acepromazine administered after exercise in horses.

The research sought to understand the sedative, cardiorespiratory, and metabolic effects of xylazine hydrochloride, detomidine hydrochloride, and a combination of xylazine and acepromazine when administered at double the standard dose to Thoroughbred horses post-exercise.

Research Methodology

• The research involved 6 adult Thoroughbred horses which were preconditioned on a treadmill to establish a uniform fitness level.
• Each horse was made to run 4 simulated races with at least 14 days intervening between each race. The treadmill speed was set to a level that made the horses exercise at 120% of their maximum oxygen consumption.
• The horses ran until they were fatigued or for a maximum of 2 minutes.
• One minute after the end of exercise, the horses were given intravenous (i.v.) treatments with xylazine (2.2 mg/kg of body weight), detomidine (0.04 mg/kg), a combination of xylazine (2.2 mg/kg) and acepromazine (0.04 mg/kg), or a saline (0.9% Sodium Chloride) solution.
• These treatments were randomized so that each horse received all treatments once, in a random order.
• Cardiopulmonary indices were measured and samples of arterial and venous blood were collected right before and at specific times for 90 minutes after each race.

Research Findings

• All the sedatives were found to produce effective sedation in the horses.
• Cardiopulmonary depression, a condition where the heart and lungs do not function optimally, was induced by the administration of these sedatives. This depression was qualitatively the same as that induced by administering these sedatives to resting horses, and was not severe.
• The administration of sedatives after exercise was found to prolong the exercise-induced increase in body temperature.

Research Conclusion

• It was concluded that administering xylazine, detomidine, or a combination of xylazine-acepromazine at twice the standard doses produces safe and effective sedation in horses that have just undergone intense, short bouts of exercise.