Furthermore, a study with 1600-mg oral dose in 5 erythromelalgia patients with a gain-of-function mutation in NaV1.7 was not decisive.9 Their reported median plasma concentration 4 and 6 hours after ingestion were above 100 μM, which is about 90-fold of our injected concentration. The gene discussed is SCN9A; the disease is erythromelalgia.