Cyanide poisoning

Cyanide poisoning is a toxic emergency in which cyanide blocks cytochrome oxidase in cells, halting aerobic respiration so that tissues cannot use oxygen. It is rare, and exposure usually follows inhalation of hydrogen cyanide gas, most often from burning plastics and other synthetic materials in fires, or ingestion of cyanide salts, certain plants and cyanogenic chemicals. Prolonged infusion of certain vasodilator drugs can also release cyanide. Symptoms begin within seconds to minutes after inhalation and include headache, giddiness, confusion, rapid breathing, flushing, nausea, convulsions and loss of consciousness, with low blood pressure and cardiac arrhythmias in severe cases. No single readily available test confirms the diagnosis, so assessment is clinical, supported by findings such as marked lactic acidosis. Treatment is urgent and covers removal from exposure, high-concentration oxygen, resuscitation and supportive care, and a cyanide antidote such as hydroxocobalamin.

Seek urgent care for severe symptoms that come on suddenly, for difficulty breathing, or for drowsiness or confusion. See a doctor when symptoms persist, keep coming back, or affect daily life. Call the local emergency number for any symptom that is sudden and severe. This page is a reference for healthcare professionals and does not replace an assessment.