Question

Given below are two statements:
Statement I: Metoprolol is a $\beta$-adrenergic receptor blocker.
Statement II: Nifedipine is a potassium channel opener.
In light of the above statements, choose the correct answer from the options given below:

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is true but Statement II is false
• D. Statement I is false but Statement II is true

Hint:

To remember this classification, look at the suffixes: drugs ending in "-olol" (like metoprolol, propranolol) are $\beta$-blockers, while dihydropyridine calcium channel blockers typically end in "-dipine" (like nifedipine, amlodipine).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Cardiovascular pharmacology involves several classes of drugs that modulate heart rate, vascular tone, and blood pressure.
These include $\beta$-adrenergic antagonists, calcium channel blockers, and potassium channel openers, each acting through distinct cellular receptors and ion channels.

Step 2: Detailed Explanation:
Let us analyze both statements in detail:
1. Statement I: Metoprolol is a $\beta$-adrenergic receptor blocker.
This statement is correct.
Metoprolol is a cardioselective $\beta_1$-adrenergic receptor antagonist.
By selectively blocking $\beta_1$-receptors in cardiac tissue, it reduces heart rate, myocardial contractility, and cardiac output, making it highly effective for treating hypertension, tachyarrhythmias, and chronic heart failure.
Therefore, Statement I is true.
2. Statement II: Nifedipine is a potassium channel opener.
This statement is incorrect.
Nifedipine belongs to the dihydropyridine class of calcium channel blockers.
It selectively inhibits L-type voltage-gated calcium channels in vascular smooth muscle cells, reducing intracellular calcium influx and causing systemic vasodilation.
It does not act as a potassium channel opener.
In contrast, potassium channel openers (such as minoxidil, pinacidil, or diazoxide) work by opening ATP-sensitive potassium channels ($K_{\text{ATP}}$), hyperpolarizing the cell membrane to cause smooth muscle relaxation.
Therefore, Statement II is false.

Step 3: Final Answer:
Statement I is true because metoprolol is a $\beta$-blocker, but Statement II is false because nifedipine is a calcium channel blocker.
Therefore, the correct option is (C).