Cyanide toxicity may be treated with all of the following except:

Cyanide toxicity may be treated with all of the following except:

• A. Sodium nitrite
• B. Hydroxycobalamin
• C. Sodium thiosulfate
• D. Methylene blue

Answer: (D)

Cyanide poisoning blocks cellular respiration by inhibiting cytochrome oxidase, so antidotes work either by binding cyanide to render it harmless or by converting cyanide into a form that can be safely excreted. Sodium nitrite helps by forming methemoglobin, which binds cyanide to make cyanomethemoglobin that’s easier to eliminate. Hydroxycobalamin directly captures cyanide to form cyanocobalamin, a non-toxic compound. Sodium thiosulfate provides sulfur to the enzyme rhodanase, transforming cyanide into thiocyanate, which is then cleared by the kidneys. Methylene blue, on the other hand, treats methemoglobinemia by reducing methemoglobin back to hemoglobin. It does not address cyanide’s mechanism and can counteract nitrite-based antidotes by reversing the beneficial methemoglobinemia, so it is not used to treat cyanide toxicity.

Cyanide poisoning blocks cellular respiration by inhibiting cytochrome oxidase, so antidotes work either by binding cyanide to render it harmless or by converting cyanide into a form that can be safely excreted. Sodium nitrite helps by forming methemoglobin, which binds cyanide to make cyanomethemoglobin that’s easier to eliminate. Hydroxycobalamin directly captures cyanide to form cyanocobalamin, a non-toxic compound. Sodium thiosulfate provides sulfur to the enzyme rhodanase, transforming cyanide into thiocyanate, which is then cleared by the kidneys. Methylene blue, on the other hand, treats methemoglobinemia by reducing methemoglobin back to hemoglobin. It does not address cyanide’s mechanism and can counteract nitrite-based antidotes by reversing the beneficial methemoglobinemia, so it is not used to treat cyanide toxicity.