Which drug inhibits Na+/K+-ATPase to increase intracellular calcium?

• A. Digoxin (digitalis)
• B. Nitrates
• C. Fenofibrate
• D. Ezetimibe

Answer: (A)

Inhibiting Na+/K+-ATPase in cardiac cells raises intracellular sodium, which slows the Na+/Ca2+ exchanger from pumping calcium out. As a result, calcium accumulates inside the cell and is more readily released during contraction, increasing the heart’s contractile strength. Digoxin (digitalis) does just that—it blocks Na+/K+-ATPase, leading to a higher intracellular calcium level and stronger cardiac contraction. This also helps slow the heart rate by increasing parasympathetic tone, which is why it’s used in certain arrhythmias, but the key mechanism for increasing intracellular calcium is ATPase inhibition. The other drugs don’t affect this pump or calcium handling in the same way: nitrates mainly dilate veins to reduce preload, while fenofibrate and ezetimibe lower cholesterol through different pathways.