Effect of acepromazine on the anesthetic requirement of halothane in the dog.

Five adult dogs were used to determine whether acepromazine maleate (ACP), administered IM, decreases the maintenance requirement of halothane and to measure any decrease for the ACP dosages of 0.02, 0.04, 0.06, 0.08, 0.10, and 0.20 mg/kg. The value minimal alveolar concentration, a measure of anesthetic potency, was used as the measure of anesthetic requirement of halothane before and after ACP was administered. All dogs were randomly exposed to each dosage of ACP, as well as to control of 0.2 ml of sterile water. At all dosages of ACP, the decrease in the minimal alveolar concentration of halothane was significant (P less than or equal to 0.05) when compared with that of the control. The decreases at the 0.04 and 0.20 mg/kg dosages were significantly (P less than or equal to 0.05) greater than those at the 0.02 and 0.06 mg/kg dosages. Halothane requirements at all other ACP dosages (0.08 and 0.10 mg/kg) were not significantly different from each other or from those at any of the other dosages. The percentage of decrease in anesthetic requirement after ACP was administered varied from 34% to 46%, with a mean decrease of 40%. The largest decrease was recorded at the dosage of 0.04 mg/kg.