A diuretic that lowers potassium taken with digoxin increases the risk of what?

• A. Hyperkalemia
• B. No effect
• C. Increased digoxin toxicity
• D. Potentially lethal arrhythmia risk from digoxin toxicity

Answer: (C)

Lowering potassium with a diuretic raises the risk of digoxin toxicity. Digoxin works by inhibiting the Na+/K+-ATPase pump in cardiac cells, and it competes with potassium for that binding site. When potassium is low, digoxin binds more readily, leading to greater inhibition of the pump, higher intracellular calcium, and heightened electrical activity in the heart. This increased effect can cause toxic consequences, including dangerous arrhythmias. So the combination of a potassium-depleting diuretic and digoxin mainly elevates the risk of digoxin toxicity.