SEDATIVE AND ANALGESIC EFFECTS OF DETOMIDINE AND ROMIFIDINE IN HORSES

In a double blind study, eight horses were treated intravenously at se ven-day intervals with detomidine at doses of 10, 20 and 10 mu g/kg, o r with romifidine at doses of 40, 80 and 120 mu g/kg, or with a placeb o solution. Their sedative and analgesic effects were evaluated by obj ective measurements and by a clinician at 15-minute intervals for thre e hours and the horses' instability in stocks, locomotor ataxia and he art rate were recorded simultaneously. The administration of both drug s at all doses resulted in sedation. The sedation achieved with romifi dine was significantly shallower and shorter-lived than with detomidin e at the recommended doses (P<0.05). The results obtained with the hig hest dose of romifidine were in some cases significantly inferior and shorter-lived than those obtained with the medium dose (P<0.05). Detom idine at the 10 mu g/kg dose was similar in its effects to the two hig hest doses of romifidine. At all doses detomidine had analgesic proper ties against the effects of electrical pain stimulation at the withers , the coronary bands on the front and hind legs, and in the perianal r egion, which were dose-dependent in depth and duration, whereas romifi dine was devoid of any analgesic effect. Instability and ataxia were m ore pronounced with detomidine than with romifidine but the effects we re only slight to moderate and not regarded as a hindrance to procedur es for which sedation is needed. Bradycardia was evident with both dru gs at all doses; its severity and duration was related to the sedative properties of the drugs and was dose related. No other side effects w ere observed.