In a patient on digoxin who is taking furosemide, which concomitant medication is most likely to contribute to symptoms such as yellow vision and tremors?

• A. Furosemide
• B. Metformin
• C. Amlodipine
• D. Atorvastatin

Answer: (A)

The important concept is that digoxin toxicity is worsened by low potassium levels. Furosemide is a loop diuretic that causes potassium loss, leading to hypokalemia. When potassium is depleted, digoxin binds more readily to the Na+/K+-ATPase pump in heart cells, increasing its effects and raising the risk of toxicity. Yellow vision and tremors are classic signs of digoxin toxicity, so taking furosemide alongside digoxin is a key contributor to these symptoms. Other drugs listed don’t have as strong a role in precipitating this toxicity through potassium loss or direct interaction with digoxin.