A quantitative assessment of pyrethroid-induced paraesthesia in the guinea-pig flank model.

Pyrethroids are known to induce cutaneous effects in man which are distinct from the classical irritation and vascular responses. These effects are characterised by transient facial burning and tingling sensations. The aetiology of this cutaneous effect is related to the ability of pyrethroids to produce trains of nerve impulses in afferent nerves by prolonging the opening of the neuronal sodium channel. The veratrum alkaloids which are structurally dissimilar to the pyrethroids are known to affect the sodium channel in a similar manner. Using the guinea-pig flank model which has been developed to study this cutaneous phenomenon we have constructed dose-response curves to three structurally related pyrethroids (permethrin, cypermethrin and deltamethrin) and to a mixture of veratrum alkaloids (veratrine). In addition we have examined the time course over which these chemicals elicit a response.