Hypotension in the horse induced by acepromazine maleate

The hypotensive effect of acepromazine maleate was related to both the dose and route of administration. The degree and duration of hypotension varied between individual horses. In general, intravenous administration produced a more rapid maximum effect than intramuscular injection and the larger the dose the longer blood pressure remained at low levels. Average systolic pressure (of 6 horses) remained significantly below control values for more than 6 h after an intramuscular injection of 0.05 mg acepromazine maleate/kg body weight. Respiratory rate was markedly decreased, with the duration, but not the degree of bradypnoea related to the dose administered. A slight, transient decrease in body temperature was observed. Heart rate was not significantly influenced by administration of acepromazine maleate.