['To investigate changes in axonal persistent Na(+) currents in patients with neuropathic pain and the effects of mexiletine, an analogue of lidocaine, on axonal excitability properties.', 'The technique of latent addition was used to estimate nodal persistent Na(+) currents in superficial radial sensory axons of 17 patients with neuropathic pain/paresthesias before and after mexiletine treatment. Brief hyperpolarizing conditioning currents were delivered, and threshold change at the conditioning-test interval of 0.2 ms was measured as an indicator of the magnitude of persistent Na(+) currents.', 'Threshold changes at 0.2 ms in latent addition were greater in the neuropathic patients than in the normal controls (p<0.001). After mexiletine treatment, there was a reduction in clinical pain scores (p<0.001), associated with decreased threshold changes at 0.2 ms (p<0.001).'] Does mexiletine suppress nodal persistent sodium currents in sensory axons of patients with neuropathic pain?