SCN9A and erythromelalgia: Although the effects of mexiletine have been investigated previously in another (V872G) NaV1.7 mutation in vitro, where it was shown to induce use-dependent current blocking effects (Choi et al., 2009), to our knowledge, this is the first evidence that the mechanism of action of mexiletine on erythromelalgia channel mutations involves an effect on their gating properties.