METOMIDATE/AZAPERONE ANAESTHESIA IN THE HORSE: A CLINICAL AND PHARMACOLOGICAL STUDY

Abstract

The hypnotic/ataractic combination of metomidate and azaperone was found to be an excellent casting agent in ponies, providing good, though short-lived, hypnosis and muscular relaxation. Intubation could readily be carried out and there were no marked changes in cardiovascular and respiratory functions. Once the animals had regained the standing position, recovery to normal consciousness was rapid. Certain undesirable features were encountered. These included a prolonged period of recumbency in some animals after sensory perception had returned, symptoms of excitability during the recovery phase in some ponies, and a small degree of haemolysis in all animals. These findings are of a preliminary nature and there are many aspects of the clinical and pharmacological effects of metomidate/azaperone that will require further study, including: 1 the cause and significance of the haemolysis, 2 the possibility of reducing the time of recumbency, without increasing the incidence of emergence excitement, by varying the dose, and the route and time of administration, of azaperone, 3 the efficacy of the drug combination in larger horses, in view of the manufacturers' suggestion that it is less satisfactory in riding horses than in ponies ; 4 the suitability of administering metomidate/azaperone as a means of inducing anaesthesia, which is to be maintained with a volatile agent such as haIothane, 5 the effects of repeated dosing with metomidate to assess the degree of accumulation.