Which electrolyte abnormality can increase the risk of digoxin toxicity?

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

Answer: (D)

Digoxin toxicity risk is shaped by the balance of electrolytes that regulate the Na+/K+ ATPase pump, since digoxin works by inhibiting that pump to boost cardiac calcium and contractility. Magnesium normally helps modulate this pump and can dampen digoxin’s effect. When magnesium is low, the pump is more easily inhibited by digoxin, so toxicity can occur at lower digoxin levels. That’s why a low magnesium level increases the risk of digoxin toxicity. Hyperkalemia is typically a consequence of toxicity rather than a predisposition, and hypermagnesemia would lessen digoxin’s effect rather than raise the risk.