Which drug is a reversible non-selective blocker of α adrenoreceptors and is used in pheochromocytoma?

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

Answer: (B)

In pheochromocytoma, blocking alpha receptors helps prevent dangerous blood pressure spikes caused by excess catecholamines. The drug described is a reversible, non-selective alpha-adrenergic blocker, meaning it blocks both α1 and α2 receptors and can be turned on and off quickly as needed. This allows rapid, titratable control of blood pressure during a pheochromocytoma crisis or diagnostic testing, with the ability to stop the effect if hemodynamics become favorable or riskier. Among options with similar roles, this drug stands apart because it is not permanently binding the receptors and it doesn’t selectively target one subtype. The irreversible option binds covalently and provides long-lasting blockade, which is useful for long-term preoperative preparation but not for acute control. A selective α1 blocker would miss the α2 component and isn’t used for pheochromocytoma, and an α2 antagonist would have opposing or different effects on sympathetic tone. Thus, the reversible non-selective alpha blocker used in pheochromocytoma is phentolamine.