A 72-year-old woman on digoxin and furosemide for chronic atrial fibrillation presents with nausea, confusion, and reports seeing halos around lights tinged yellow-green. ECG shows frequent ventricular ectopy. Which electrolyte disturbance most likely precipitated this presentation?

• A Hyperkalemia from spironolactone addition
• B Hypokalemia from diuretic therapy ✓
• C Hypermagnesemia from antacid use
• D Hypernatremia from inadequate water intake

Explanation

Loop diuretic induced hypokalemia is the classic precipitant of digitalis toxicity because low extracellular potassium reduces competition at the Na+/K+-ATPase binding site, effectively increasing digoxin binding. The gastrointestinal symptoms, visual disturbances with xanthopsia, and ventricular ectopy complete the picture. Hyperkalemia occurs in acute massive digoxin overdose rather than chronic potentiation, and magnesium deficiency, not excess, also predisposes to toxicity.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.