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Digoxin toxicity — ABIM Board MCQ

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ModerateCardiovascularDigoxin toxicityABIM Board

An 81-year-old woman with atrial fibrillation and stage 3b chronic kidney disease takes a stable dose of digoxin. After several days of poor oral intake, she develops nausea, confusion, and yellow-green visual halos. Her serum creatinine is 2.8 mg/dL, increased from a baseline of 1.4 mg/dL. Potassium is 5.4 mEq/L, and a serum digoxin concentration obtained 12 hours after her last dose is elevated. ECG shows atrial tachycardia with variable atrioventricular block. She has taken no extra doses and has started no new medications. Which of the following most likely caused her digoxin toxicity?

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Correct answer: B — Reduced renal clearance of digoxin

The correct answer is B. This patient has chronic digoxin toxicity caused by acute kidney injury superimposed on chronic kidney disease. Digoxin is eliminated predominantly by the kidneys, so reduced renal function prolongs its half-life and causes accumulation even when the prescribed dose is unchanged. Nausea, confusion, altered color vision, and atrial tachycardia with AV block are characteristic manifestations. Hyperkalemia may accompany significant toxicity. Hypokalemia can increase myocardial sensitivity to digoxin but is absent here and would not explain the elevated drug concentration. Increased hepatic metabolism, hyperthyroidism-associated increased clearance, and increased intestinal P-glycoprotein efflux would tend to reduce digoxin exposure rather than cause accumulation.

Reference: US Food and Drug Administration. Digoxin Oral Solution Prescribing Information, sections 5.5, 8.5, 8.7, and 10.1. 2025. https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/021648s013lbl.pdf