EVALUATION OF THE ARRHYTHMOGENICITY OF A LOW-DOSE OF ACEPROMAZINE - COMPARISON WITH XYLAZINE

Alteration in the arrhythmogenic dose of epinephrine (ADE) was determi ned in 6 healthy dogs under halothane anesthesia following the adminis tration of xylazine at 1.1 mg/kg IV and acepromazine at 0.025 mg/kg IV . The order of treatment was randomly assigned with each dog receiving both treatments and testing was carried out on 2 separate occasions w ith at least a 1 wk interval. The ADE determinations were made prior t o drug administration during halothane anesthesia (CNTL) and then 20 m in and 4 h following drug treatment. Epinephrine was infused for 3 min at increasing dose rates (2.5, 5.0, 10.0 mu g/kg/min) until the arrhy thmia criterion (4 or more intermittent or continuous premature ventri cular contractions) was reached within the 3 min of infusion or the 1 min following cessation, The interinfusion interval was 20 min. There was a significant difference (P = 0.0001) in the ADE determined follow ing acepromazine administration at 20 min (20.95 mu g/kg +/- 2.28 SEM) compared to CNTL (6.64 mu g/kg +/- 1.09), xylazine at 20 min (5.82 mu g/kg +/- 0.95) and 4 h (6.13 mu g/kg +/- 1.05), and acepromazine at 4 h (7.32 mu g/kg +/- 0.34). No other significant differences existed ( P < 0.05). In this study we were unable to show any sensitization to e pinephrine following xylazine administration during halothane anesthes ia, while a protective effect was shown with a low dose of acepromazin e.