A patient receiving high-dose intravenous sodium nitroprusside infusion for hypertensive emergency for four days develops metabolic acidosis, confusion, and seizures. The definitive antidotal treatment is:

• A N-acetylcysteine
• B Methylene blue
• C Flumazenil
• D Sodium thiosulfate with oxygen therapy ✓

Explanation

Nitroprusside metabolism releases cyanide ions, which inhibit cytochrome oxidase and cause lactic acidosis; prolonged infusions also produce thiocyanate toxicity with neurological features, especially in renal failure. Cyanide poisoning is treated with sodium thiosulfate, which donates sulfur for conversion of cyanide to thiocyanate by rhodanese, combined with high-flow oxygen. N-acetylcysteine treats paracetamol injury, flumazenil reverses benzodiazepines, and methylene blue treats methemoglobinemia.

Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.