Which electrolyte abnormality is associated with an increased risk for digoxin toxicity?

• A. Hypercalcemia
• B. Hypokalemia
• C. Hypermagnesemia
• D. Hyponatremia

Answer: (B)

Low potassium levels raise the risk of digoxin toxicity because potassium and digoxin compete for the same binding site on the Na+/K+-ATPase pump. When extracellular potassium is low, more of the pump sites are available for digoxin to bind, increasing inhibition of the pump. This amplifies digoxin’s effects on cardiac cells, heightening the chances of dangerous arrhythmias and toxicity symptoms. In contrast, hyperkalemia is typically a sign of severe digoxin toxicity rather than a predisposing factor, and the other electrolyte abnormalities don’t have the same well-established relationship with toxicity risk. In patients taking digoxin, maintaining normal potassium helps limit toxicity risk.