What is the definitive treatment for digoxin toxicity in an adult patient?

Definitive Treatment for Digoxin Toxicity

Administer digoxin-specific antibody fragments (digoxin-Fab) immediately for life-threatening digoxin toxicity—this is the definitive treatment with Class I recommendation from the American Heart Association. 1

Indications for Digoxin-Fab Administration

Life-threatening manifestations requiring immediate digoxin-Fab include: 1, 2, 3

• Sustained ventricular tachycardia or ventricular fibrillation
• Progressive bradyarrhythmias or second/third-degree heart block unresponsive to atropine
• Cardiac arrest or asystole
• Hyperkalemia >5.5 mEq/L in adults (>6 mEq/L in children) with rapidly progressive toxicity symptoms
• Hemodynamic instability with elevated digoxin concentration
• Serum digoxin concentration >4 ng/mL with serious arrhythmias

Dosing Strategy

Acute Poisoning with Unknown Amount

• Start with 20 vials (800 mg) for adults if amount ingested is unknown and patient has life-threatening toxicity 4
• For imminent cardiac arrest, full neutralizing dose is justified 5
• Alternative titrated approach: Give 80 mg (2 vials) initially, repeat as needed based on clinical response within 1-2 hours 5, 6
• Most patients require less than half the calculated neutralizing dose with this strategy 5

Chronic Toxicity

• Give 40 mg (1 vial) initially for adults ≥20 kg 4, 5
• Repeat after 60 minutes if no clinical response, sooner if clinically unstable 5, 6
• Generally 40-120 mg (1-3 vials) total is sufficient 5
• For children <20 kg, start with 1 vial 4

Calculated Dosing (When Amount Known)

• Dose (vials) = Amount ingested (mg) ÷ 0.5 mg/vial 4
• Dose (vials) = [Serum digoxin (ng/mL) × weight (kg)] ÷ 100 4
• Each 40 mg vial binds approximately 0.5 mg digoxin 4, 5

Expected Response and Monitoring

Clinical improvement occurs rapidly: 1, 2, 3

• Dysrhythmia resolution in 30-45 minutes in most cases 1
• Response rates of 50-90% in observational studies 1
• Free digoxin concentration falls to near zero within minutes 5
• Survival rate of 54% even in patients presenting with cardiac arrest 1, 2

Post-treatment monitoring is essential: 2, 3

• Watch for rebound toxicity over 24-48 hours 3
• Monitor for exacerbation of heart failure 3
• Monitor for increased ventricular rate in atrial fibrillation 3
• Watch potassium levels closely as they can shift dramatically 3
• Serum digoxin measurements are unreliable after Fab administration (measures bound + unbound digoxin) 2

Supportive Management

Correct electrolyte abnormalities immediately: 2, 3

• Maintain serum potassium 4.0-5.5 mEq/L 2
• Correct hypomagnesemia 2
• Ensure adequate oxygenation 2

Temporizing measures while awaiting digoxin-Fab: 1

• Atropine may be reasonable for bradydysrhythmias (Class IIb recommendation) 1
• Temporary cardiac pacing may be reasonable but has 36% complication rate and may require higher-than-normal current 1
• Lidocaine or phenytoin may be reasonable for ventricular dysrhythmias until Fab can be administered (Class IIb) 1

Treatments That Do NOT Work

Do not use the following for digoxin removal: 1, 3

• Hemodialysis (Class III: No Benefit) 1
• Hemofiltration 1
• Hemoperfusion 1
• Plasmapheresis 1

These are ineffective because digoxin has a large volume of distribution (5-10 L/kg), making extracorporeal removal futile 1, 5

Critical Pitfalls to Avoid

Do not delay treatment waiting for confirmatory digoxin levels if clinical presentation suggests life-threatening toxicity 3

Do not administer IV calcium to digitalized patients—this can precipitate serious arrhythmias 3

Do not assume toxicity is ruled out by "therapeutic" digoxin levels—toxicity can occur at levels <2 ng/mL in the presence of hypokalemia, hypomagnesemia, hypothyroidism, or renal dysfunction 1, 2

If patient fails to respond to adequate digoxin-Fab dose, question the diagnosis of digoxin toxicity 4