SUMMARY

Ventricular tachycardia was produced in the dog by intravenous injection of 2-3 (j.g/kg of adrenaline during nitrous oxide-halothane anaesthesia. On a weight basis, propio-mazine was found to be as effective as perphenazine in preventing the arrhythmias. Promethazine and promazine showed similar effects in much higher doses. The protec-tion provided by all these drugs could be surmounted by doses of adrenaline of 4-6 [Ag/kg. Propiomazine did not produce any action on blood pressure whereas the other drugs tested produced a prolonged fall in pressure in all the experiments. Since the clinical dose of propiomazine is 2-4 times that of perphenazine, it is possible that the former may prove superior to the latter in clinical trials. The occurrence of adrenaline-induced ventricular arrhythmias under halothane anaesthesia in the dog and in man is well documented (Raventos