Comparative local anaesthetic and antiarrhythmic actions of levamisole hydrochloride and lignocaine hydrochloride.

Using the guinea-pig wheal preparation for determining the degree of infiltration anaesthesia, lignocaine was found to be 2 times more potent than levamisole. Lignocaine was, however, 1.27 times more toxic than levamisole in the mouse. It is suggested that levamisole could be used as a local anaesthetic agent for infiltration anaesthesia. As regards surface anaesthesia, lignocaine was 16.6 times more potent than levamisole. Levamisole would, therefore, not be of use in surface anaesthesia. Levamisole was more effective than lignocaine in protecting toads against deaths due to the minimum dose of ouabain which caused 100% mortality. The therapeutic indices for levamisole and lignocaine were 4.57 and 1.58 respectively. Unlike with lignocaine it was possible to achieve more than 50% protection with levamisole. Levamisole was, however, only marginally more effective than lignocaine in reverting to sinus rhythm, barium chloride-induced ventricular dysrhythmia in the rat. It is suggested that levamisole could have potential value as an antiarrhythmic agent.