Which drug class blocks calcium entry into cardiac cells, decreasing contractility and automaticity, with a negative dromotropic effect and causing vasodilation?

Which drug class blocks calcium entry into cardiac cells, decreasing contractility and automaticity, with a negative dromotropic effect and causing vasodilation?

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

Answer: (A)

Calcium channel blockers block L-type calcium channels, reducing calcium entry into cardiac and smooth muscle cells. In the heart, less calcium means weaker muscle contractions (negative inotropy) and slower depolarization in pacemaker and conduction tissues, which lowers automaticity and slows conduction through the AV node (negative dromotropy). In vascular smooth muscle, decreased intracellular calcium causes relaxation, leading to vasodilation and lower systemic vascular resistance. Together these effects explain why this drug class decreases contractility and automaticity, slows AV conduction, and causes vasodilation. Other classes don’t produce this combination of direct calcium-entry blockade in both heart and vessels, so they don’t fit the described effects.

Calcium channel blockers block L-type calcium channels, reducing calcium entry into cardiac and smooth muscle cells. In the heart, less calcium means weaker muscle contractions (negative inotropy) and slower depolarization in pacemaker and conduction tissues, which lowers automaticity and slows conduction through the AV node (negative dromotropy). In vascular smooth muscle, decreased intracellular calcium causes relaxation, leading to vasodilation and lower systemic vascular resistance. Together these effects explain why this drug class decreases contractility and automaticity, slows AV conduction, and causes vasodilation. Other classes don’t produce this combination of direct calcium-entry blockade in both heart and vessels, so they don’t fit the described effects.