A 57-year-old man with hypertensive emergency is managed with a continuous infusion for BP control. After 60 hours of therapy he develops confusion, seizures, and worsening lactic acidosis with a high anion gap. He also has advanced chronic kidney disease. Which agent is responsible for this complication?

• A Fenoldopam
• B Nicardipine
• C Esmolol
• D Sodium nitroprusside ✓

Explanation

Sodium nitroprusside metabolism releases cyanide, which is normally converted to thiocyanate by hepatic rhodanese using thiosulfate. With prolonged infusion, high doses, liver disease, or impaired thiocyanate clearance from renal failure, cyanide accumulates, inhibits cytochrome oxidase, and produces anaerobic metabolism with refractory lactic acidosis and neurotoxicity. Treatment includes stopping the drug plus thiosulfate or hydroxocobalamin. Nicardipine, esmolol and fenoldopam lack this metabolic liability.

Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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