Tetrodotoxin is a quinazoline alkaloid that is a marine toxin isolated from fish such as puffer fish. It has been shown to exhibit potential neutotoxicity due to its ability to block voltage-gated sodium channels. It has a role as a voltage-gated sodium channel blocker, a neurotoxin, a marine metabolite, an animal metabolite and a bacterial metabolite. It is a quinazoline alkaloid, an azatetracycloalkane and an oxatetracycloalkane. It is a conjugate base of a tetrodotoxin(1+).