The comparative effects of prilocaine, lignocaine and cocaine on the response of the rabbit ear artery to adrenaline and noradrenaline.

The effects of prilocaine, lignocaine or cocaine together with either adrenaline or noradrenaline was tested by applying combinations of these preparations to an isolated rabbit ear artery and measuring changes in intra-arterial pressure. Potentiation of the response was greatest with combinations of local anaesthetic and adrenaline; with noradrenaline the response was significantly potentiated only when the lowest concentrations of cocaine were used. It is suggested that some of this effect could be attributed to the differential inhibition by the local anaesthetic agents of the neuronal uptake of the catecholamines. This inhibition was prominent with all combination which contained adrenaline, but only occurred with noradrenaline when that vasoconstrictor agent was combined with cocaine.