Autonomic Pharmacology USMLE Step 1 Practice Question
A 42-year-old man with hypertension and benign prostatic hyperplasia is started on doxazosin. Thirty minutes after the first dose, he experiences dizziness and syncope upon standing. Vital signs show BP 92/58 mmHg, HR 108 bpm, RR 16, temp 37.2°C, and SpO2 98% on room air. His wife notes facial flushing. He denies chest pain or shortness of breath. Recent labs show normal electrolytes and creatinine. Which of the following best explains this adverse effect?
Answer choices
- Aβ-adrenergic receptor antagonism causing reflex tachycardia
- BMuscarinic receptor blockade producing anticholinergic effects
- CUnopposed α2-adrenergic agonism leading to vasoconstriction
- DInhibition of phosphodiesterase leading to cAMP accumulation
- EFirst-dose effect causing profound vasodilation and orthostatic hypotensionCorrect answer
- FInhibition of angiotensin-converting enzyme causing acute reduction in angiotensin II-mediated vasoconstriction
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.