Toxicology USMLE Step 1 Practice Question
A 59-year-old man receiving high-dose nitroprusside for hypertensive emergency (BP 210/120 mmHg, HR 102, RR 18, SpO2 98% on room air) becomes progressively confused over 6 hours. Laboratory studies reveal severe lactic acidosis (pH 7.21, lactate 8.2 mmol/L) despite adequate oxygenation and normal renal function. He denies chest pain and has no focal neurologic deficits. Which of the following best explains this complication?
Answer choices
- AGeneration of cyanide with inhibition of cytochrome oxidaseCorrect answer
- BAccumulation of NAPQI
- CInhibition of aldehyde dehydrogenase
- DAcetylcholinesterase inhibition
- EDirect oxidation of hemoglobin iron to Fe3+ only
- FInhibition of pyruvate dehydrogenase with shunting of pyruvate to lactate
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.