A diuretic decreases potassium; what effect on digoxin?

• A. Increase the serum digoxin sensitivity level
• B. Decrease the serum digoxin sensitivity level
• C. Not have any effect on the serum digoxin sensitivity level
• D. Cause a low average serum digoxin sensitivity level

Answer: (A)

Potassium levels influence how strongly digoxin works. Digoxin inhibits the Na+/K+-ATPase pump, and when potassium is low due to a diuretic, there’s less competition for that binding site. The result is greater digoxin binding and a stronger inotropic effect, which translates to increased sensitivity to digoxin and a higher risk of toxicity at the same serum concentration. In other words, a diuretic that lowers potassium makes the body more responsive to digoxin. Conversely, keeping potassium normal or high can lessen digoxin’s effect. This is why monitoring potassium and digoxin levels is important when patients are on diuretics and digoxin, and why signs of digoxin toxicity (like bradycardia, nausea, or visual changes) require attention and possible intervention.