Cyanide poisoning

Cyanide poisoning

Cyanide poisoning occurs when a living organism is exposed to cyanide. The cyanide ion, if used as poison, is generally delivered in the form of gaseous hydrogen cyanide or in the form of potassium cyanide or sodium cyanide.

Acute poisoning

Inhalation of high concentrations of cyanide causes a coma with seizures, apnea and cardiac arrest, with death following in a matter of minutes. At lower doses, loss of consciousness may be preceded by general weakness, giddiness, headaches, vertigo, confusion, and perceived difficulty in breathing. At the first stages of unconsciousness, breathing is often sufficient or even rapid, although the state of the victim progresses towards a deep coma, sometimes accompanied by pulmonary edema, and finally cardiac arrest. Skin colour goes pink from high blood oxygen saturation.

Chronic exposure

Exposure to lower levels of cyanide over a long period (e.g., after use of cassava roots as a primary food source in tropical Africa) results in increased blood cyanide levels, which can result in weakness and a variety of symptoms, including permanent paralysis.

Treatment of poisoning and antidotes

The United States standard cyanide antidote kit first uses a small inhaled dose of amyl nitrite, followed by intravenous sodium nitrite, followed by intravenous sodium thiosulfate. The nitrites oxidize some of the hemoglobin's iron from the ferrous state to the ferric state, converting the hemoglobin into methemoglobin. (Treatment with nitrites is not innocuous as methemoglobin cannot carry oxygen). Cyanide preferentially bonds to methemoglobin rather than the cytochrome oxidase, converting methemoglobin into cyanmethemoglobin. In the last step, the intravenous sodium thiosulfate converts the cyanmethemoglobin to thiocyanate, sulfite, and hemoglobin. The thiocyanate is excreted.

Alternative methods of treating cyanide intoxication are used in other countries. For example, in France hydroxycobalamin (a form of vitamin B12) is used to bind cyanide to form the harmless vitamin B12a cyanocobalamin. Cyanocobalamin is eliminated through the urine. Hydroxycobalamin works both within the intravascular space and within the cells to combat cyanide intoxication. This versatility contrasts with methemoglobin, which acts only within the vascular space as an antidote. Administration of sodium thiosulfate improves the ability of the hydroxycobalamin to detoxify cyanide poisoning. This treatment is considered so effective and innocuous that it is administered routinely in Paris to victims of smoke inhalation to detoxify any associated cyanide intoxication. However it is relatively expensive and not universally available.

4-Dimethylaminophenol (4-DMAP) has been proposed in Germany as a more rapid antidote than nitrites with (reportedly) lower toxicity. 4-DMAP is used currently by the German military and by the civilian population. In humans, intravenous injection of 3 mg/kg of 4-DMAP produces 35 percent methemoglobin levels within 1 minute. Reportedly, 4-DMAP is part of the US Cyanokit, while it is not part of the GERM Cyanokit due to side effects (e. g. hemolysis).

Cobalt salts have also been demonstrated as effective in binding cyanide. One current cobalt-based antidote available in Europe is dicobalt edetate or dicobalt-EDTA, sold as Kelocyanor. This agent chelates cyanide as the cobalticyanide. This drug provides an antidote effect more quickly than formation of methemoglobin, but a clear superiority to methemoglobin formation has not been demonstrated. Cobalt complexes are quite toxic, and there have been accidents reported in the UK where patients have been given dicobalt-EDTA by mistake based on a false diagnoses of cyanide poisoning.

The International Programme on Chemical Safety issued a survey (IPCS/CEC Evaluation of Antidotes Series) that lists the following antidotal agents and their effects: Oxygen, sodium thiosulfate, amyl nitrite, sodium nitrite, 4-dimethylaminophenol, hydroxocobalamin, and dicobalt edetate ('Kelocyanor'), as well as several others Other commonly-recommended antidotes are 'solutions A and B' (a solution of ferrous sulfate in aqueous citric acid, and aqueous sodium carbonate) and amyl nitrite.

Britain's Health and Safety Executive (HSE) has recommended against the use of solutions A and B because of their limited shelf life, potential to cause iron poisoning, and limited applicability (effective only in cases of cyanide ingestion, whereas the main modes of poisoning are inhalation and skin contact). The HSE has also questioned the usefulness of amyl nitrite due to storage/availability problems, risk of abuse, and lack of evidence of significant benefits, instead recommending Kelocyanor

Evidence from animal experiments suggests that coadministration of glucose protects against cobalt toxicity associated with the antidote agent dicobalt edetate. For this reason, glucose is often administered alongside this agent (e.g. in the formulation 'Kelocyanor').

It has also been anecdotally suggested that glucose is itself an effective counteragent to cyanide, reacting with it to form less toxic compounds that can be eliminated by the body. One theory on the apparent immunity of Grigory Rasputin to cyanide was that his killers put the poison in sweet pastries and madeira wine, both of which are rich in sugar; thus, Rasputin would have been administered the poison together with massive quantities of antidote. One study found a reduction in cyanide toxicity in mice when the cyanide was first mixed with glucose However, as yet glucose on its own is not an officially acknowledged antidote to cyanide poisoning.

Cyanide occurs in some foodstuffs, in small amounts. These are disposed of by enzymatic metabolism with rhodanase, combining cyanide with thiosulfate to produce comparatively harmless thiocyanate. Oral preparations of rhodanase are proposed as prophyllaxis and acute treatment for cyanide poisoining, currently under clinical trials.

Historical cases

Gas chambers

Hydrogen cyanide gas was the agent used during the Nazi regime in Germany for mass murder in some gas chambers during the Holocaust. It was released from Zyklon B pellets, which were a commercial biocide. It was also used in US execution chambers, where it was generated by reaction between potassium cyanide dropped into a compartment containing sulfuric acid directly below the chair in the chamber.


Cyanides were stockpiled in both the Soviet and the United States chemical weapons arsenals in the 1950s and 1960s. During the Cold War, the Soviet Union was thought to be planning to use hydrogen cyanide as a "blitzkrieg" weapon to clear a path through the opposing front line, knowing that the hydrogen cyanide would dissipate and allow unprotected access to the captured zone. However, as a military agent, hydrogen cyanide was not considered very effective, since it is lighter than air and needs a significant dose to incapacitate or kill.

Although there have been no verified instances of its use as a weapon, hydrogen cyanide may have been employed by Iraq in the war against Iran and against the Kurds in northern Iraq during the 1980s.


Cyanide salts are sometimes used as fast-acting suicide devices. Cyanide is reputed to work faster on an empty stomach, possibly because the anion is protonated by stomach acids to give HCN. Famous cyanide salt suicides include:

Members of the Liberation Tigers of Tamil Eelam which operate in north-eastern Sri Lanka are probably the most reported to use capsules made out of cyanide compound/compounds, where each member of the militia wears a capsule round their neck, which is used to commit suicide when they are about to be captured by the security forces of Sri Lanka.

Jonestown, Guyana was the site of a large mass suicide/murder, where 913 members of the Peoples Temple drank potassium cyanide-laced Flavor Aid in 1978.




In 2003, Al Qaeda reportedly planned to release cyanide gas into the New York City Subway system. The attack was reportedly aborted because there would not be enough casualties.

In 1995 a device was discovered in a restroom in the Kayabacho Tokyo subway station consisting of bags of sodium cyanide and sulfuric acid with a remote controlled motor to rupture them in what was believed to be an attempt to produce toxic amounts of hydrogen cyanide gas by the Aum Shinrikyo cult

In fiction

Poisoning by cyanide figures prominently in crime fiction, for example Agatha Christie's Sparkling Cyanide (also entitled Remembered Death) and And Then There Were None. Cyanide is also the instrument of murder in The Big Sleep by Raymond Chandler, "The Cradle Will Fall" by Mary Higgins Clark and Roald Dahl's short story "The Landlady". In the Joseph Kesselring play "Arsenic and Old Lace", two old ladies mix wine with arsenic, cyanide and strychnine to use to kill old men. In the book "Hit Man: A Technical Manual for Independent Contractors", the use of cyanide to poison a mark is explained in detail.

Though not as famous as his Joker toxin or his electric joy-buzzers, the Joker from Batman comics is also known to use cyanide pies as one of his "comedic" weapons.

Australian author Nevil Shute's novel about life after nuclear war, On the Beach, gives the scenario of the Australian government giving survivors free cyanide tablets to commit suicide rather than face death from radiation poisoning.

In the James Bond movies and novels, 00 agents are issued cyanide capsules for use in the event of capture by the enemy. James Bond is described as having thrown his away. Assassins in the films have also used cyanide as a quick suicide method such as Mr. Jones in Dr. No, and in The Spy Who Loved Me, British and American nuclear submarines are threatened with the injection of Cyanide gas to force their crews to surrender to the villain's henchmen.

In The 12.30 from Croydon a 1934 novel by Freeman Wills Crofts, the protagonist kills his uncle by cleverly inserting a fake pill carved from cyanide of potassium, into the old-man's medicine bottle.

In the TV series 24 there are many instances where terrorists will bite a cyanide capsule to avoid harsh interrogation.

Satirical song writer Tom Lehrer managed to work this toxin into a line in his song "Poisoning Pigeons in the Park": When they see us coming / The birdies all try an' hide / But they still go for peanuts / When coated with cyan-hide.

Potassium cyanide is also the main ingredient in the fake death pill from the Hideo Kojima game Metal Gear Solid 3: Snake Eater. It is an essential item to be used by Naked Snake in an emergency; it puts Naked Snake into a near-death state until he recovers himself using a revival pill. If he is left in the near-death state for too long then he will die.

In Phoenix Wright: Ace Attorney - Trials and Tribulations, the third case solved by the player involves a programmer who is murdered when potassium cyanide is slipped into his coffee at a restaurant.

Potassium cyanide was also featured in the novel and movie Battle Royale. Provided with a sample of the substance to use as a weapon, Yuko Sakaki, one of the female characters, employs the toxin to poison the spaghetti of another character. The tainted food reaches an unintended recipient in the form of Yuka Nakagawa, triggering the events in the infamous lighthouse scene.

Potassium cyanide is also used as a method of suicide in Shutter, an American remake of a Thai horror film.

See also


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