Abstract

The antifibrillary action of mephentermine sulfate has been investigated under conditions of immersion hypothermia in dogs. The incidence of hypothermic ventricular fibrillation was reduced significantly from 91 per cent in 33 control dogs to 37 per cent in 19 dogs treated with mephentermine (3 to 5 mgm./kgm.). The protective action of this agent is not exerted at the expense of a depressed pacemaker since dogs treated with mephentermine could be cooled to lower temperatures than untreated control animals. A higher arterial pressure was observed in all dogs following the injection of mephentermine at a rectal temperature of 25°C. This pressor effect apparently was unrelated to its antifibrilary action, since no difference in blood pressure was noted between the mephentermine-treated dogs which fibrillated and those which were protected.