Pharmacology · single question

Atenolol is a commonly used antihypertensive. Its mechanism of action is BEST described as:

Alpha-1 adrenergic blocker → peripheral vasodilation
Non-selective beta-1 and beta-2 blocker
Calcium channel blocker → reduces vascular resistance
Cardioselective beta-1 adrenergic blocker → decreases heart rate and cardiac output

Show answer and explanation

Correct answer: D. Cardioselective beta-1 adrenergic blocker → decreases heart rate and cardiac output

A. Alpha-1 blockade (prazosin, doxazosin) causes peripheral vasodilation — not the mechanism of atenolol.
B. Non-selective beta blockers (propranolol) block both beta-1 and beta-2. Atenolol's cardioselectivity is its key feature.
C. Calcium channel blockers (amlodipine, nifedipine) block calcium channels in smooth muscle — not beta receptors.
D. Correct. Atenolol is a CARDIOSELECTIVE beta-1 blocker — it primarily blocks beta-1 receptors in the heart with minimal effect on beta-2 receptors (bronchi, peripheral vasculature). This reduces heart rate, contractility, and cardiac output, lowering blood pressure. Because it is cardioselective, it is relatively safer in asthmatic patients (though still used with caution).

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