Mutations in the Nav1.7 encoding gene Scn9a are associated with various pain disorders, such as inherited erythromelalgia, paroxysmal extreme pain disorder and small-fiber neuropathy.70 Inhibiting Nav1.7 functions effectively mitigates neuropathic pain and stimulates the production of endogenous opioids.71 The role of Nav1.7 varies with different types of pain. This evidence concerns the gene SCN9A and paroxysmal extreme pain disorder.