Alpha adrenergic blocking agent used as a vasodilator?

Alpha adrenergic blocking agent used as a vasodilator?

• A. Phentolamine
• B. Yohimbine
• C. Prazosin
• D. Phenoxybenzamine

Answer: (D)

Blocking alpha receptors on vascular smooth muscle stops catecholamine-induced vasoconstriction, producing vasodilation. Phenoxybenzamine is the best answer because it irreversibly blocks both alpha-1 and alpha-2 receptors, giving a long-lasting, diffuse vasodilator effect. This prolonged action is especially useful in situations like preoperative management of pheochromocytoma to prevent hypertensive crises. In contrast, the other agents are either shorter-acting (phentolamine), more alpha-1 selective (prazosin), or act on alpha-2 receptors (yohimbine) and don’t provide the same broad, sustained vasodilation.

Blocking alpha receptors on vascular smooth muscle stops catecholamine-induced vasoconstriction, producing vasodilation. Phenoxybenzamine is the best answer because it irreversibly blocks both alpha-1 and alpha-2 receptors, giving a long-lasting, diffuse vasodilator effect. This prolonged action is especially useful in situations like preoperative management of pheochromocytoma to prevent hypertensive crises. In contrast, the other agents are either shorter-acting (phentolamine), more alpha-1 selective (prazosin), or act on alpha-2 receptors (yohimbine) and don’t provide the same broad, sustained vasodilation.