Bitter almond odor on the breath of a patient exposed to smoke suggests cyanide poisoning; the best treatment is which agent?

• A. Atropine
• B. Pyridoxine
• C. Deferoxamine
• D. Sodium nitrite

Answer: (D)

Cyanide poisoning stops cells from using oxygen by inhibiting cytochrome oxidase, so tissues become hypoxic even with normal blood oxygen levels. In smoke inhalation, this is a key concern. Sodium nitrite works by inducing methemoglobinemia; methemoglobin has a high affinity for cyanide and binds it to form cyanomethemoglobin, freeing cytochrome oxidase to resume aerobic metabolism. This rapid shift helps restore cellular respiration. In many protocols, sodium nitrite is paired with sodium thiosulfate to help convert cyanide to thiocyanate for excretion, but the essential first-step antidote is nitrite. The other agents listed address different toxicities (anticholinergic, INH-related, iron chelation) and aren’t antidotes for cyanide poisoning.