What is the antidote used to treat cyanide poisoning?

• A. Hydroxocobalamin
• B. Atropine
• C. Pralidoxime
• D. Dimercaprol

Answer: (A)

Cyanide blocks cellular respiration by inhibiting cytochrome c oxidase, so tissues can’t use oxygen even when blood oxygen is normal. Hydroxocobalamin provides a rapid antidote by binding cyanide to form cyanocobalamin (a form of vitamin B12) that is safely excreted. This detoxifies cyanide quickly, allowing oxidative phosphorylation to resume and tissues to regain oxygen use. It’s given intravenously and has a favorable safety profile, making it a preferred immediate treatment. Other agents mentioned are for different poisonings: atropine to counteract muscarinic effects in cholinergic toxidromes, pralidoxime to reactivate acetylcholinesterase in organophosphate poisoning, and dimercaprol to chelate certain metals.