Which drug produces alpha-adrenergic receptor and beta-adrenergic receptor blockade?

Which drug produces alpha-adrenergic receptor and beta-adrenergic receptor blockade?

• A. Captopril
• B. Hydralazine
• C. Minoxidil
• D. Labetalol

Answer: (D)

The main idea being tested is that some drugs can block both alpha-adrenergic and beta-adrenergic receptors, producing a combined hemodynamic effect. Labetalol does just that: it acts as a nonselective antagonist at both alpha-1 receptors and beta receptors. By blocking alpha-1 receptors, it causes vasodilation of peripheral arteries, lowering systemic vascular resistance and blood pressure. By blocking beta receptors, it reduces heart rate and contractility, and lowers renin release, which further helps decrease blood pressure. The combination helps achieve a smoother blood pressure reduction with less reflex tachycardia than would occur with a single-mechanism vasodilator. This dual blockade makes labetalol particularly useful in hypertensive emergencies and pregnancy-related hypertension. The other agents listed lower blood pressure through different pathways—for example, ACE inhibitors reduce angiotensin II formation, while direct vasodilators lower pressure by dilating vessels without adrenergic receptor blockade, so they don’t provide the dual receptor blockade.

The main idea being tested is that some drugs can block both alpha-adrenergic and beta-adrenergic receptors, producing a combined hemodynamic effect. Labetalol does just that: it acts as a nonselective antagonist at both alpha-1 receptors and beta receptors. By blocking alpha-1 receptors, it causes vasodilation of peripheral arteries, lowering systemic vascular resistance and blood pressure. By blocking beta receptors, it reduces heart rate and contractility, and lowers renin release, which further helps decrease blood pressure. The combination helps achieve a smoother blood pressure reduction with less reflex tachycardia than would occur with a single-mechanism vasodilator. This dual blockade makes labetalol particularly useful in hypertensive emergencies and pregnancy-related hypertension. The other agents listed lower blood pressure through different pathways—for example, ACE inhibitors reduce angiotensin II formation, while direct vasodilators lower pressure by dilating vessels without adrenergic receptor blockade, so they don’t provide the dual receptor blockade.