Responses of horses to acepromazine maleate administered orally in a paste

The effects of acepromazine maleate (ACP), given orally in a paste form, were examined in six standard-bred geldings over a 12 hour period. Three dose rates, zero (placebo paste), 0.13 mg kg-1 and 0.26 mg kg-1, given before or after feeding, were investigated. The data were divided into two sampling periods for analysis, one from zero to 120 minutes and the other from four to 12 hours. Sedation was assessed by a score (TS score) based on general appearance, anal sphincter relaxation and penile protrusion. This TS score was significantly elevated 40 minutes after dosing with ACP, irrespective of whether the horses had been fed or not. Dose rate had no significant effect on TS in the zero to 120 minute sampling period, but the TS score was significantly (P less than 0.01) higher at the higher dose rate in the four to 12 hour period. At both dose rates, the TS scores were still significantly higher than their pretreatment values 12 hours after dosing. Systolic blood pressure (SBP), measured indirectly from the coccygeal artery, haematocrit (PCV) and total plasma protein concentration (TPP) were also examined. ACP caused significant falls in SBP and PCV, but the effect was complicated by feeding. ACP given after feeding had a reduced effect on SBP and PCV. Feeding appeared to cause a rise then a fall in PCV and TPP which was superimposed upon the fall caused by ACP. There was no difference between the two dose rates of ACP on SBP and PCV.(ABSTRACT TRUNCATED AT 250 WORDS)