Potassium Cyanide - Toxicity

Toxicity

KCN can be detoxified most efficiently with hydrogen peroxide:

KCN + H₂O₂ → KOCN + H₂O

Cyanide is a potent inhibitor of cellular respiration, acting on mitochondrial cytochrome c oxidase and hence blocking oxidative phosphorylation. This prevents the body from oxidizing food to produce useful energy. Lactic acidosis then occurs as a consequence of anaerobic metabolism. Initially, acute cyanide poisoning causes a red or ruddy complexion in the victim because the tissues are not able to use the oxygen in the blood. The effects of potassium and sodium cyanide are identical. The person loses consciousness, and death eventually follows over a period of time. During this period, convulsions may occur. Death occurs not by cardiac arrest, but by hypoxia of neural tissue.

The lethal dose for potassium cyanide is 200-300 mg. The toxicity of potassium cyanide when ingested depends on the acidity of the stomach, because it must react with an acid to become hydrogen cyanide, the deadly form of cyanide. Grigori Rasputin may have survived a potassium cyanide poisoning because his stomach acidity was unusually low.

A number of prominent persons were killed or committed suicide using potassium cyanide, including members of the Black Hand and members of the Nazi Party, such as Hermann Göring and Heinrich Himmler, World War II era British agents (using purpose-made suicide pills), computer scientist Alan Turing, and various religious cult suicides such as by the Peoples Temple and Heaven's Gate. Also members of the LTTE involved in the assassination of Indian prime minister Rajiv Gandhi committed suicide using potassium cyanide. Potassium cyanide (and other forms of cyanide) is a popular method of murder in fiction, especially in the books written by Agatha Christie.