Which drug class blocks calcium entry into cardiac cells, decreasing contraction and causing vasodilation?

Which drug class blocks calcium entry into cardiac cells, decreasing contraction and causing vasodilation?

• A. Calcium Channel Blockers
• B. Sodium Channel Blockers
• C. Potassium Channel Blockers
• D. Beta Blockers

Answer: (A)

Calcium entry is essential for both heart muscle contraction and the tone of vascular smooth muscle. Drugs that block L-type calcium channels prevent calcium from entering cardiac cells and smooth muscle cells. With less intracellular calcium, the heart contracts more weakly (negative inotropy), and the smooth muscle relaxes, leading to vasodilation. The combined effect is a lower cardiac workload and reduced blood pressure due to decreased afterload and systemic vascular resistance. This is exactly what calcium channel blockers do. Other drug classes act by different mechanisms—sodium channel blockers affect depolarization, potassium channel blockers affect repolarization, and beta blockers blunt sympathetic stimulation—so they don’t produce the same direct calcium-entry blockade.

Calcium entry is essential for both heart muscle contraction and the tone of vascular smooth muscle. Drugs that block L-type calcium channels prevent calcium from entering cardiac cells and smooth muscle cells. With less intracellular calcium, the heart contracts more weakly (negative inotropy), and the smooth muscle relaxes, leading to vasodilation. The combined effect is a lower cardiac workload and reduced blood pressure due to decreased afterload and systemic vascular resistance. This is exactly what calcium channel blockers do. Other drug classes act by different mechanisms—sodium channel blockers affect depolarization, potassium channel blockers affect repolarization, and beta blockers blunt sympathetic stimulation—so they don’t produce the same direct calcium-entry blockade.