Cyanide poisoning

Cyanide poisoning (also known as cyanide toxicity or hydrocyanic acid poisoning) is a potentially life-threatening condition caused by exposure to cyanide compounds, which may occur through inhalation (hydrogen cyanide gas), ingestion (cyanide salts such as potassium cyanide or sodium cyanide), or skin absorption. Cyanide is also released during combustion of certain synthetic materials, making smoke inhalation from fires a common source of exposure. Cyanide exerts its toxic effects by binding to cytochrome c oxidase (complex IV) in the mitochondrial electron transport chain, thereby blocking aerobic cellular respiration. This results in cellular hypoxia despite adequate oxygen delivery, forcing cells into anaerobic metabolism and causing lactic acidosis. The body systems most severely affected include the central nervous system and cardiovascular system, as these are highly dependent on oxidative metabolism. Key clinical features develop rapidly and include headache, dizziness, confusion, seizures, loss of consciousness, and coma. Cardiovascular manifestations include initial tachycardia and hypertension followed by bradycardia, hypotension, and cardiac arrest. Patients may exhibit cherry-red skin coloration (though this is not always present), rapid breathing progressing to respiratory failure, and a characteristic bitter almond odor on the breath. Severe metabolic (lactic) acidosis with an elevated anion gap is a hallmark laboratory finding. The condition can progress to death within minutes to hours depending on the dose and route of exposure. Treatment requires immediate intervention and includes supportive care with high-flow oxygen, decontamination when appropriate, and administration of specific antidotes. Approved antidotes include hydroxocobalamin (Cyanokit), which directly binds cyanide to form cyanocobalamin (vitamin B12), and the older cyanide antidote kit consisting of amyl nitrite, sodium nitrite, and sodium thiosulfate. Hydroxocobalamin is generally preferred due to its favorable safety profile. Sodium thiosulfate enhances the body's natural detoxification pathway by providing sulfur for the enzyme rhodanese, which converts cyanide to the less toxic thiocyanate. Early recognition and prompt antidote administration are critical for survival.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

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