Comparative antiarrhythmic and local anaesthetic effects of piperazine citrate and lignocaine hydrochloride.

The effect of pretreatment with lignocaine hydrochloride (0.1 mg/g body weight) and piperazine citrate (1 mg/g body weight) on the number of deaths due to ouabain (0.02-0.12 mg/g body weight) was determined in the toad. Lignocaine was at least 10 times more potent than piperazine. Considering the doses that gave 50% protection from the 100% deaths due to ouabain (0.09 mg/g), lignocaine was 14.8 times more potent, but it was 56-60 times more toxic than piperazine as shown by the LD50s in the mouse and toad. Lignocaine was also about 10 times more potent than piperazine in preventing electrically-induced arrhythmia in the isolated guinea-pig atrium suspended in low potassium Ringer-Locke solution. With regard to infiltration anaesthesia, lignocaine was about 158 times more potent than piperazine. Therefore the relative potencies of the antiarrhythmic activities of piperazine and lignocaine do not correlate with the relative local anaesthetic potencies. It was concluded that, although lignocaine is 10-15 times more potent than piperazine as an antiarrhythmic agent, piperazine should be a much safer drug and could have potential utility as a substitute for lignocaine as an antiarrhythmic agent.