Pharmacology CMS Practice Test

Cardiac glycosides such as digoxin produce which of the following effects on the heart?

Increased force of myocardial contraction Vasodilation of peripheral arteries Increased urine output Decreased blood pressure

Correct Answer:

Increased force of myocardial contraction

Explanation:

Cardiac glycosides produce a strong positive inotropic effect by blocking the Na+/K+ ATPase pump in cardiac muscle cells. This raises intracellular sodium, which reduces the activity of the Na+/Ca2+ exchanger that normally removes calcium from the cell. With less calcium being expelled, intracellular calcium accumulates, increasing calcium availability for the contractile machinery during systole and thereby strengthening each heartbeat. This direct increase in force of contraction is the hallmark effect of digoxin on the heart. The other options aren’t the primary cardiac actions of digoxin. It does not act as a direct vasodilator of peripheral arteries, and increases in urine output or decreases in blood pressure aren’t primary effects of its action on the myocardium.

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