Differentiate dihydropyridine and non-dihydropyridine calcium channel blockers in terms of primary use and effect on heart rate.

• A. Dihydropyridines primarily vasodilate with minimal effect on heart rate.
• B. Dihydropyridines primarily affect the heart, lowering heart rate and contractility.
• C. Non-dihydropyridines are used mainly for hypertension with minimal cardiac effects.
• D. Non-dihydropyridines primarily dilate vascular smooth muscle.

Answer: (A)

Dihydropyridines mainly block calcium channels in vascular smooth muscle, especially arteries, so their primary effect is potent arterial vasodilation. This lowers blood pressure with little direct impact on the heart’s rate or force of contraction (though reflex tachycardia can occur from the drop in BP). Non-dihydropyridines, like verapamil and diltiazem, have stronger actions on the heart itself: they slow SA node firing, slow AV nodal conduction, and reduce myocardial contractility, which lowers heart rate and can affect cardiac output. Therefore, the statement that dihydropyridines primarily vasodilate with minimal effect on heart rate best captures the distinction. The other options mix up where these drugs act and how they affect heart rate.