Different pathophysiologic mechanisms are responsible for the development of chronic pain disorders. Pain pathways are triggered in part by ectopic discharges of voltage-sensitive sodium channels, which are in abundance in both the peripheral and the central nervous systems. Tetrodotoxin (TTX) is a selective blocker of Na+ channels and causes analgesia either by decreasing the propagation of action potentials by Na+ channels and/or by blocking of ectopic discharges associated with chronic pain. TTX is extracted from the puffer fish (fugu). Results from animal pharmacology studies revealed that TTX is a more potent analgesic than standard analgesic agents such as aspirin, morphine or meperidine.