 This is in contrast with the genetic basis of primary erythromelalgia in which the disorder results from gain-of-function mutations.Local anesthetics such as lidocaine, but also the anticonvulsant phenytoin, mediate their analgesic effects by non-selectively blocking voltage-gated sodium channels.Nav1.7, as well as Nav1.3, Nav1.8, and Nav1.9, are the specific channels that have been implicated in pain signaling.