Toxicology USMLE Step 1 Practice Question

A 79-year-old man with a history of chronic systolic heart failure and atrial fibrillation presents to the emergency department with a 2-day history of nausea, vomiting, confusion, and yellow-tinged vision. His current medications include digoxin 0.25 mg daily and furosemide 40 mg daily. Vital signs reveal BP 128/76 mmHg, HR 102 bpm with an irregular rhythm, RR 18 breaths/min, and temperature 37°C. On examination, he appears lethargic and mildly diaphoretic. Serum digoxin level is 3.2 ng/mL (therapeutic range: 0.5–2.0 ng/mL), BUN is 28 mg/dL, and creatinine is 1.8 mg/dL, suggesting mild renal impairment contributing to drug accumulation. Serum potassium is 4.1 mEq/L. ECG demonstrates frequent premature ventricular contractions with occasional bigeminy. Which agent is most appropriate for treatment of this patient's severe digoxin toxicity?