Which statement best describes the primary site of action of dihydropyridine calcium channel blockers?

• A. Non-dihydropyridines primarily affect the heart with negative inotropy.
• B. They block the Na+/K+-ATPase in myocardium.
• C. They primarily cause arteriolar vasodilation with limited cardiac effects.
• D. They inhibit the RAAS system.

Answer: (C)

Dihydropyridine calcium channel blockers mainly target vascular smooth muscle in arterioles. By blocking L-type calcium channels, they reduce calcium influx into these smooth muscle cells, leading to relaxation and dilation of arterioles. This vasodilation lowers systemic vascular resistance and blood pressure with relatively little direct effect on the heart’s contractility or conduction. That’s why the best description is that they primarily cause arteriolar vasodilation with limited cardiac effects. The other statements don’t fit because Na+/K+-ATPase inhibition is the action of digitalis on the myocardium, RAAS inhibitors affect the renin-angiotensin system, and non-dihydropyridines have more pronounced effects on the heart (negative inotropy and chronotropy) rather than selective vascular dilation.