COMPARISON OF THE SEDATIVE EFFECTS OF MEDETOMIDINE AND XYLAZINE IN HORSES

The sedative effects in horses of the new alpha-2 agonist medetomidine were compared with those of xylazine. Four ponies and one horse were treated on separate occasions with two doses of medetomidine (5-mu-g/kg bodyweight and 10-mu-g/kg bodyweight) and with one dose of xylazine (1 mg/kg bodyweight) given by intravenous injection. Medetomidine at 10-mu-g/kg was similar to 1 mg/kg xylazine in its sedative effect but produced more severe and more prolonged ataxia, and one animal fell over during the study. Medetomidine at 5-mu-g/kg produced less sedation but a similar degree of ataxia to 1 mg/kg xylazine.