A 45-year-old with pheochromocytoma is scheduled for surgery. Prior to giving propranolol for tachycardia, an alpha-blocker must be given first because propranolol alone would cause:

• A Severe hypotension from blockade of beta-2 mediated vasodilation in skeletal muscle
• B Reflex bradycardia worsening cardiac output
• C Paradoxical hypertensive crisis from unopposed alpha-adrenergic stimulation ✓
• D Bronchospasm from beta-2 blockade in the lung

Explanation

Catecholamines from pheochromocytoma stimulate both alpha and beta receptors. In the presence of a beta-blocker, beta-2-mediated vasodilation is blocked while alpha-1-mediated vasoconstriction remains unopposed, producing a dangerous paradoxical hypertensive crisis. Phenoxybenzamine or doxazosin (alpha-blockade) must be established first to prevent this complication before adding a beta-blocker.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.