What percentage of patients show digoxin toxicity at some point?

• A. 5%
• B. 20%
• C. 40%
• D. 60%

Answer: (B)

Digoxin has a narrow therapeutic index, so the risk of toxicity persists for many patients over the course of treatment. Because clearance is largely renal and because small changes in kidney function, electrolyte balance, or drug interactions can push levels from therapeutic to toxic, a substantial minority will experience some toxicity at some point. The figure commonly cited is about 20% of patients, including both overt symptoms and milder, subclinical effects detectable on exams or labs. This is why careful monitoring of digoxin levels, renal function, and electrolytes (especially potassium and magnesium), along with awareness of interacting drugs, is essential during therapy. The other percentages are too low or too high compared with what is typically observed in clinical practice.