A 78-year-old female taking digoxin and furosemide presents with nausea, yellow-green visual halos (xanthopsia), and ventricular ectopy. Serum potassium is 6.2 mEq/L. What is the specific antidote?

Answer and explanation

Correct answer: A. Digoxin immune Fab antibody fragments

  1. Step 1: Digoxin inhibits myocardial Na+/K+ ATPase, which causes intracellular sodium accumulation and extracellular potassium elevation in severe acute toxicity.
  2. Step 2: Digoxin-specific antibody fragments (DigiFab) bind free intravascular digoxin with high affinity, neutralizing toxicity and reversing cardiac arrhythmias.
Answer
Digoxin immune Fab antibody fragments.
Why not the others: Intravenous calcium is contraindicated in digoxin toxicity because high intracellular calcium can trigger fatal ventricular fibrillation ('stone heart'). Potassium infusion would worsen dangerous hyperkalemia. Activated charcoal is ineffective once systemic absorption has occurred.

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