Objective assessment of detomidine-induced analgesia and sedation in the horse

Abstract

The effects of detomidine, a veterinary sedative analgesic, were studied in the horse. Novel objective techniques were employed to assess the analgesic and sedative potency of this compound. Intravenous doses of 0.010, 0.020 and 0.040 mg/kg were administered to eight adult Thoroughbred racehorses according to a double-blind crossover design. Analgesia was measured by determining the latency to onset of the skin twitch and hoof withdrawal reflexes following noxious thermal stimulation of the withers and fetlock, respectively. Sedation was assessed by quantifying spontaneous locomotor activity in horses confined to an activity chamber, and by electronic measurement of head ptosis. Linear, dose-related increases in the intensity and duration of analgesia were observed. However, dose-related increases in duration, rather than intensity of sedation were observed. In conclusion, detomidine is an effective analgesic in the horse, but it is more potent in producing sedation than analgesia.