Autonomic Pharmacology USMLE Step 1 Practice Question
A 68-year-old man with hypertension presents to the emergency department with acute onset chest pain, diaphoresis, and dyspnea. Vital signs are BP 210/135 mmHg, HR 125/min, RR 24/min, O2 saturation 94% on room air. Physical examination reveals an anxious, diaphoretic patient with clear lungs. ECG shows sinus tachycardia without ischemic changes. Troponin is negative. The patient is administered intravenous labetalol for hypertensive emergency. Which of the following best explains the pharmacologic advantage of labetalol over a pure beta-blocker in this clinical scenario?
Answer choices
- ABeta-1 selectivity prevents bronchospasm and allows unopposed alpha-2 receptor activation
- BCombined alpha and beta-adrenergic blockade produces vasodilation while preventing reflex tachycardiaCorrect answer
- CIntrinsic sympathomimetic activity maintains cardiac output and prevents hypotension
- DSelective beta-2 blockade in coronary vessels improves myocardial perfusion
- EDual inhibition of ACE and renin-angiotensin system reduces afterload
- FAlpha-1 blockade causes direct coronary vasodilation without beta-receptor involvement
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