Tetrodotoxin (TTX) is an amino-perhydroquinazoline compound and one of the most potent neurotoxins found in nature. It selectively and potently blocks sodium channels on excitable neural membranes. TTX is a low-molecular-weight, non-protein neurotoxin, with a toxicity more than 1,250 times greater than that of highly toxic sodium cyanide. A dose of just 0.5 mg can be fatal to humans. Tetrodotoxin causes local irritation in the intestinal tract and, after absorption, rapidly acts on nerve endings and the central nervous system, impairing nerve conduction and leading to paralysis and death. TTX is heat-stable and cannot be destroyed by salting or sun-drying. It decomposes only when heated at high temperatures for more than 30 minutes or under alkaline conditions. Heating at 220°C for 20–60 minutes completely destroys the toxin. The incubation period for TTX poisoning is very short, ranging from as little as 10–30 minutes to up to 3–6 hours. The onset of symptoms is rapid, and without timely treatment, the fastest death can occur within 10 minutes, while the longest may take 4–6 hours.

Tetrodotoxin also has pharmacological value, exhibiting analgesic and local anesthetic effects, as well as anti-cancer properties, making it a therapeutic agent for advanced-stage cancer treatment.