ACEPROMAZINE-XYLAZINE COMBINATION IN DOGS - ANTAGONISM WITH 4-AMINOPYRIDINE AND YOHIMBINE

  • 1 January 1983
    • journal article
    • research article
    • Vol. 44  (11) , 2037-2042
Abstract
Groups of fasted atropinized crossbred dogs of both sexes were injected i.m. with a standard dosage of a xylazine-acepromazine combination (2.2 and 0.5 mg/kg, respectively). Righting reflex was uniformly lost and considered to be the point of maximum sedation. After maximal sedation, dogs were injected i.v. with 4-aminopyridine (4-AP, 0.5 mg/kg), yohimbine (0.25 mg/kg) or a combination of 4-AP and yohimbine. Controls were given 1 ml of saline solution i.v. The 4-AP, yohimbine and 4-AP + yohimbine significantly reduced walk times (time to arousal and ability to walk on a leash) from a control value of 43.1 to 7.6, 4.4 and 1.9 min, respectively (P < 0.05). Relapse to unconsciousness did not occur with any antagonist regimen and recovery was uneventful. In 3 dogs sedated with the xylazine-acepromazine combination supplemented with halothane having surgically placed cannulas and electrodes for measurement of EEC, ECG and electromyographic (EMG) responses, arterial blood pressure and respiratory rates and depth, i.v. injection of 4-AP + yohimbine causes transient femoral arterial hypotension with tachycardia, increases in respiratory rate, depth, and minute volume, increased EMG and EEG activities preceding and accompanying gross movements, slight speeding of ECG, and behavioral arousal within 3 min. Increased heart rate was also observed in intact dogs given yohimbine. Increased rate and depth of respiration was also seen in all intact dogs given antagonists. The xylazine-acepromazine combination did not induce arterial hypotension as expected from the product literature. To what extent pretreatment with atropine sulfate may have counteracted this effect is unknown. Apparently, the xylazine-acepromazine combination produced a state of relaxation, immobility, deep sedation and moderate analgesia that could be useful in restraint, preanesthetic medication and minor surgical procedures in veterinary medicine. A major advantage of this sedative combination is that it can be safely antagonized with 4-AP and yohimbine.