A 72-year-old man with a 5-year history of benign prostatic hyperplasia and hypertension presents to the emergency department with syncope that occurred 30 minutes after taking his first dose of prazosin. He was standing at the bathroom sink when he felt lightheaded, experienced palpitations, and then lost consciousness briefly. He regained consciousness within seconds. His wife reports he was on hydrochlorothiazide for blood pressure control. Vital signs on arrival: supine BP 168/98 mmHg, HR 106 bpm; standing BP 112/62 mmHg, HR 118 bpm. Physical examination reveals mild diaphoresis but is otherwise unremarkable. Laboratory studies show sodium 138 mEq/L, potassium 3.8 mEq/L, and creatinine 1.0 mg/dL. Which of the following best explains the mechanism of this adverse drug effect?

1. A)Activation of baroreceptor reflexes leading to unopposed alpha-1 adrenergic stimulation and vasoconstriction
2. B)Blockade of alpha-1 adrenergic receptors on vascular smooth muscle with unopposed beta-2 mediated reflex tachycardia and relative hypovolemiaGABARITO
3. C)Inhibition of norepinephrine reuptake in sympathetic nerve terminals causing catecholamine accumulation
4. D)Direct inhibition of cardiac myocyte contractility through negative inotropic effects
5. E)Acute hypokalemia from concurrent diuretic use causing prolonged QT interval and torsades de pointes