Digoxin toxicity risk increases with which electrolyte abnormality?

• A. Hyperkalemia
• B. Hypokalemia
• C. Hypomagnesemia
• D. Hypercalcemia

Answer: (B)

The risk of digoxin toxicity increases when potassium levels are low because both potassium and digoxin compete for the same binding site on the Na+/K+-ATPase pump. When potassium is deficient, more of the pump sites are available for digoxin to bind, enhancing its inhibitory effect. This stronger inhibition raises intracellular calcium, which can trigger dangerous arrhythmias and other toxicity signs. Maintaining normal potassium helps limit digoxin’s binding and reduces toxicity risk. It’s also common to see hyperkalemia emerge during significant digoxin toxicity due to the pump’s sustained inhibition, underscoring why potassium balance is important in patients taking digoxin.