Cyanide is a poison that has been used throughout time and is linked to such infamous people as Napoleon, Adolph Hitler, and Jim Jones. There are 4 forms of cyanide that may serve as chemical weapons: cyanogen chloride (CNCl), hydrocyanic acid (hydrogen cyanide, HCN), cyanogen bromide (CNBr), and cyanogen iodide (CNI). The signs and symptoms may be difficult to differentiate from those of other chemical warfare agents.

Hydrogen cyanide gas, the most toxic product of combustion, is a significant hazard in smoke inhalation – especially in closed-space fires – and is the most common cause of acute cyanide poisoning.

Cyanide acts as a systemic cellular asphyxiant. It inhibits cytochrome oxidase A3, thus inhibiting normal cellular respiration. This prevents normal oxygen use in the body and results in anaerobic metabolism with the generation of lactic acid.

The latency period for cyanides is from 10-15 seconds up to several minutes. Exposure is via inhalation or ingestion. Improperly prepared cassava has been linked to an outbreak of suspected cyanide poisoning in Uganda. Cyanogen chloride is an irritant and may produce lacrimation and upper airway irritation. When exposed to low concentrations of the other 3 forms of cyanide, victims will have 10-15 seconds of gasping, tachypnea, tachycardia, headache, giddiness, and dizziness, followed by nausea, vomiting, agitation, and confusion.

At higher concentrations, the victim will have all the above-mentioned initial signs and symptoms followed quickly by bradycardia, apnea, seizures, shock, coma, and death. Pupils may be unresponsive and dilated, but this is not specific to cyanide poisoning.

Timely supportive care and antidote administration are critical for survival in patients poisoned by cyanide.