Cyanide poisoning

Cyanide poisoning is a life-threatening toxicity resulting from exposure to cyanide ions, which inhibit cellular respiration by blocking mitochondrial cytochrome c oxidase, leading to rapid cellular hypoxia and metabolic failure.

Cyanide binds to the ferric ion (Fe³⁺) in cytochrome c oxidase (complex IV) within the mitochondrial electron transport chain, inhibiting oxidative phosphorylation and halting ATP production. This blockade forces cells into anaerobic metabolism, resulting in lactic acidosis and rapid energy failure. The toxic effects are rapid in onset and systemic, often leading to cardiovascular collapse, seizures, coma, and death if not promptly treated.

Cyanide poisoning is rare in the US, with 208 cases reported to the American Association of Poison Control Centers in 2023.

Risk factors include exposure to smoke from residential or industrial fires or fumes, occupational contact with cyanide-containing compounds (such as in mining, metallurgy, or chemical industries including textile, paper, and plastic manufacturing), ingestion of cyanogenic plants (such as bitter almonds, apricot or peach seeds, cassava roots, lima beans, bamboo shoots) or compounds, and intentional ingestion or inhalation in suicide or homicide attempts.

Onset of symptoms is often rapid, including headache, dizziness, confusion, dyspnea, nausea, and seizures, progressing to cardiovascular instability, respiratory failure, and coma. Without immediate treatment, such as administration of hydroxocobalamin, sodium nitrite, or sodium thiosulfate, the condition may rapidly become fatal. Early recognition and prompt antidotal therapy are critical for survival and neurological recovery.