Which antidote is used for cyanide poisoning and typical dose?

• A. Hydroxocobalamin 5 g IV; may be repeated
• B. Sodium nitrite 12 g IV; may be repeated
• C. Amyl nitrite inhalation
• D. N-acetylcysteine 140 mg/kg IV

Answer: (A)

When cyanide poisoning is suspected, the antidote strategy centers on removing cyanide from its toxic site of action by binding it so that cells can resume aerobic metabolism. Hydroxocobalamin does this directly and rapidly: it binds cyanide to form cyanocobalamin (vitamin B12), which the body can then excrete. This direct, high-affinity binding makes it the most effective and fastest-acting antidote for cyanide exposure, and it avoids the risks associated with other approaches. The typical adult dose is 5 grams given IV, and it can be repeated if symptoms or acidosis persist or worsen.

Other options either work indirectly or carry more risks in cyanide poisoning. Sodium nitrite induces methemoglobinemia to sequester cyanide, but that reduces the blood’s oxygen-carrying capacity and can cause dangerous hypotension or hypoxia, especially in seriously ill patients. Amyl nitrite is an older inhaled agent with limited and slower efficacy in modern practice. N-acetylcysteine is specific to acetaminophen poisoning and has no role in cyanide detoxification.