Pharmacology · single question

A patient takes metoprolol for cardiovascular disease. What is the mechanism of action of this medication?

Blocks alpha-1 receptors causing vasodilation
Selectively blocks beta-1 adrenergic receptors, reducing heart rate and myocardial contractility
Inhibits ACE, reducing angiotensin II production
Blocks calcium channels in vascular smooth muscle

Show answer and explanation

Correct answer: B. Selectively blocks beta-1 adrenergic receptors, reducing heart rate and myocardial contractility

A. Incorrect. Alpha-1 blockers (prazosin) cause vasodilation. Metoprolol is a beta-blocker.
B. Correct. Metoprolol is a cardioselective BETA-1 blocker. It reduces heart rate (negative chronotropy) and contractility (negative inotropy), decreasing cardiac output and blood pressure — reducing cardiac workload.
C. Incorrect. ACE inhibitors (lisinopril, enalapril) block angiotensin-converting enzyme. Not metoprolol's MOA.
D. Incorrect. Calcium channel blockers (amlodipine, verapamil) block L-type calcium channels. Not metoprolol's MOA.

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