Which electrolyte abnormality commonly potentiates digoxin toxicity in patients taking digoxin with loop diuretics?

Which electrolyte abnormality commonly potentiates digoxin toxicity in patients taking digoxin with loop diuretics?

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

Answer: (A)

Digoxin toxicity risk rises when potassium is low because digoxin binds more strongly to the Na+/K+-ATPase pump when extracellular potassium is decreased. Loop diuretics cause potassium loss, leading to hypokalemia. With less K+ around, digoxin’s inhibition of the pump is enhanced, raising intracellular calcium via the Na+/Ca2+ exchanger and making the myocardium more irritable. This combination increases the chances of dangerous arrhythmias and toxicity. Hyperkalemia wouldn’t have this effect; it actually reduces digoxin binding. Hyponatremia isn’t the main driver here, and while low magnesium can predispose to digoxin toxicity, the classic and most relevant interaction with loop diuretics is hypokalemia.

Digoxin toxicity risk rises when potassium is low because digoxin binds more strongly to the Na+/K+-ATPase pump when extracellular potassium is decreased. Loop diuretics cause potassium loss, leading to hypokalemia. With less K+ around, digoxin’s inhibition of the pump is enhanced, raising intracellular calcium via the Na+/Ca2+ exchanger and making the myocardium more irritable. This combination increases the chances of dangerous arrhythmias and toxicity.

Hyperkalemia wouldn’t have this effect; it actually reduces digoxin binding. Hyponatremia isn’t the main driver here, and while low magnesium can predispose to digoxin toxicity, the classic and most relevant interaction with loop diuretics is hypokalemia.