A hypertensive emergency is managed with an intravenous vasodilator titrated by infusion pump. After 72 hours the patient becomes confused with metabolic acidosis and the infusion must be stopped. Which toxicity explains this presentation?

• A Thiocyanate and cyanide accumulation from metabolism of the drug ✓
• B Reflex catecholamine surge causing myocardial ischemia
• C Iodine induced thyroid storm
• D Hemolytic anemia from glucose 6 phosphate dehydrogenase deficiency

Explanation

Sodium nitroprusside is metabolized to cyanide, which is converted to thiocyanate by the liver and excreted renally. Prolonged infusion, high doses, or renal impairment leads to cyanide toxicity presenting as lactic acidosis, confusion and refractory hypotension, and to thiocyanate toxicity causing psychosis. Treatment includes stopping the drug, thiosulfate, and hydroxocobalamin. Iodine relates to amiodarone, and hemolysis is a concern with dapsone or primaquine, not nitroprusside.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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