EFFECTS OF XYLAZINE GIVEN INTRAVENOUSLY TO HORSES

Xylazine (0.8 mg/kg, body weight) was given intravenously to four horses and to three horses which were administered atropine sulfate (0.5 mg/head) intravenously 25 minutes before xylazine was given. Transient increase in systolic and diastolic arterial blood pressures, and brady cardia with atrioventricular block (A-V) were induced by xylazine. Bradycardia and A-V block were prevented by injection of atropine sulfate. In one horse, A-V block was present before treatment and the frequency of occurrence was increased signifificantly by the administration of xylazine. Blood pressure which initially increased tended to decrease to less than control values. There was no significant change in the partial pressure of blood gases or in the blood pH during the study period (60 minutes after administration of xylazine) .Atropine sulfate should be administered before xylazine is given. It is desirable to use xylazine more carefully to the horse which has some abnormality in E.C.G..