Which electrolyte abnormality increases the risk of digoxin toxicity?

Which electrolyte abnormality increases the risk of digoxin toxicity?

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

Answer: (D)

Low potassium levels heighten digoxin toxicity because digoxin binds more readily to the Na+/K+ ATPase pump when extracellular K+ is low. The pump is blocked by digoxin, and with less potassium competing for the binding site, more pumps are inhibited. This leads to increased intracellular calcium via reduced activity of the Na+/Ca2+ exchanger, promoting stronger contractions but also triggering dangerous arrhythmias. That higher binding and calcium loading explain why hypokalemia raises the risk of toxicity. Hyperkalemia, by contrast, makes it harder for digoxin to bind the pump and is often a consequence of digoxin toxicity rather than a predisposing factor. Hyponatremia or hypercalcemia are not as directly tied to the toxicity risk as potassium is, with the strongest, most consistent link being low potassium.

Low potassium levels heighten digoxin toxicity because digoxin binds more readily to the Na+/K+ ATPase pump when extracellular K+ is low. The pump is blocked by digoxin, and with less potassium competing for the binding site, more pumps are inhibited. This leads to increased intracellular calcium via reduced activity of the Na+/Ca2+ exchanger, promoting stronger contractions but also triggering dangerous arrhythmias. That higher binding and calcium loading explain why hypokalemia raises the risk of toxicity. Hyperkalemia, by contrast, makes it harder for digoxin to bind the pump and is often a consequence of digoxin toxicity rather than a predisposing factor. Hyponatremia or hypercalcemia are not as directly tied to the toxicity risk as potassium is, with the strongest, most consistent link being low potassium.