A patient with pheochromocytoma crisis is given an alpha-blocker before beta-blocker therapy. If beta-blocker is administered first without prior alpha-blockade, which hemodynamic consequence occurs?
- A Severe bradycardia only with no change in blood pressure
- B Reflex tachycardia due to baroreceptor activation
- C Paradoxical hypertensive crisis due to unopposed alpha-adrenergic vasoconstriction ✓
- D Hypotensive crisis due to combined alpha and beta blockade
Correct answer: C. Paradoxical hypertensive crisis due to unopposed alpha-adrenergic vasoconstriction
Explanation
In pheochromocytoma, catecholamine excess acts on both alpha- and beta-receptors. Beta-blockers remove cardiac beta1-mediated vasodilation and beta2-mediated peripheral vasodilation, leaving only alpha1-mediated intense vasoconstriction unopposed, causing paradoxical severe hypertension. Alpha-blockade must precede beta-blockade to avoid this life-threatening complication. Options B, C, and D do not describe the correct pathophysiology of this dangerous drug-disease interaction.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
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