What is the primary mechanism through which dihydropyridine calcium-channel blockers reduce blood pressure?

• A. Decrease heart rate
• B. Decrease cardiac output
• C. Decrease peripheral resistance
• D. Decrease blood volume

Answer: (C)

Dihydropyridine calcium-channel blockers primarily reduce blood pressure through the mechanism of decreasing peripheral resistance. These medications work by selectively blocking L-type calcium channels on vascular smooth muscle cells, leading to relaxation and dilation of blood vessels. This vasodilation reduces the resistance that the heart must work against to pump blood, ultimately resulting in a decrease in blood pressure.

When peripheral resistance is lowered, there is less constriction in the arterioles and arteries, which allows blood to flow more freely. This reduction in resistance is critical in managing hypertension, as elevated peripheral resistance is a key factor contributing to high blood pressure.

While other factors, such as heart rate and cardiac output, do play roles in blood pressure regulation, the primary effect of dihydropyridine calcium-channel blockers is the significant vasodilatory action that directly decreases peripheral resistance. This makes option C the most accurate choice in this context.