A 60-year-old patient with pheochromocytoma is undergoing preoperative preparation. Which sequence of adrenergic blockade is mandatory and why?
- A α-blocker first, then β-blocker if needed; β-blockade alone can cause paradoxical hypertension through unopposed α effects ✓
- B β-blocker first, then α-blocker; β-blockade reduces catecholamine synthesis
- C Simultaneous α- and β-blockade to prevent reflex tachycardia from the start
- D β-blocker first to prevent tachycardia, then α-blocker if blood pressure remains high
Correct answer: A. α-blocker first, then β-blocker if needed; β-blockade alone can cause paradoxical hypertension through unopposed α effects
Explanation
In pheochromocytoma, catecholamine excess acts on both α and β receptors. If a β-blocker is given first, it removes β2-mediated vasodilation while leaving α-mediated vasoconstriction intact, causing paradoxical and potentially fatal hypertension. Therefore, an α-blocker (phenoxybenzamine is preferred for its non-competitive, long-duration action; or prazosin) is started first for at least 10–14 days, followed by a β-blocker only if tachycardia persists. This principle is a classic high-yield pharmacology decision point.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.