Inhibits sodium channels Nav1.7/SCN9A and potassium channels Kv11.1/KCNH2. Also binds the voltage-sensor domain of the potassium channel KvAP (from the archaeon Aeropyrum pernix) with very slow apparent binding kinetics and affects channel gating. Reaches its target by dynamically partitioning into anionic or zwitterionic headgroup lipid membranes. May bind to the open state of KvAP