Sedative and analgesic effects of medetomidine in dogs

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Abstract
The sedative and analgesic effects of medetomidine were studied in 18 laboratory beagles in a randomized cross-over study which was carried out in a double-blind fashion. Xylazine was included as a positive control and placebo as a negative control. Medetomidine was used at doses of 10, 30, 90 and 180 .mu.g/kg i.m. compared to a dose of 2.2 mg/kg xylazine i.m. Parameters closely related to sedation wre used to measure the degree of sedation. These were a posture variable (including evaluation of the dog''s posture without external disturbance and resistance when laid recumbent) and a relaxation variable (including relaxation of the jaws, upper eyelids and anal sphincter). The first signs of sedation were recorded 1.5-3.5 min after administration of both drugs. The dogs sat down at 0.6-2.6 min post-injectionand became prone at 1.9-5.9 min. Medetomidine dose-dependently affected the posture of the dogs and the relaxation variable-the higher the dose, the stronger and longer lasting the effect recorded. The sedative effect of xylazine was comparable to a medetomidine dose of 30 .mu.g/kg. The analgesic effect was assessed as changes in the response to superficial pain induced by electrical stimuli. The response threshold increased significantly with both drugs and the effect of medetomidine was dose-dependent. The effects of the doses of 30 .mu.g/kg medetomidine and 2.2 mg/kg xylazine did not differ significantly. In summary, medetomidine possessed an excellent sedative effect associated with analgesia in dogs.