Workup and Management of Suspected Digoxin Toxicity

Clinical Presentation

The American College of Cardiology notes that typical arrhythmias suggestive of digoxin toxicity include enhanced atrial, junctional, or ventricular automaticity, often combined with atrioventricular block 1
Ventricular tachycardia that is fascicular or bidirectional in origin is particularly suggestive of digoxin toxicity, as stated by the American College of Cardiology 1
Severe digoxin overdose can cause hyperkalemia and cardiac standstill, according to the American College of Cardiology 1

The American College of Cardiology recommends measuring serum potassium, magnesium, and calcium, as electrolyte abnormalities can contribute to digoxin toxicity 1, 2, 3
Hyperkalemia (>5.0 mEq/L) is a marker of severity in acute digoxin poisoning and is associated with poor prognosis, as reported in Circulation 4

The American College of Cardiology recommends discontinuing digoxin and monitoring cardiac rhythm in cases of mild toxicity 1
For moderate to severe toxicity, the American Heart Association suggests considering atropine administration for bradydysrhythmias, and lidocaine or phenytoin for ventricular dysrhythmias, until digoxin-Fab can be administered, as stated in Circulation 5
The American College of Cardiology advises administering digoxin-specific antibody fragments (digoxin-Fab) for severe toxicity, particularly with serum digoxin concentrations exceeding 4 ng/mL, serious arrhythmias, hyperkalemia >5.0 mEq/L, or hemodynamic instability 1, 2, 4

The dosing of digoxin-Fab is based on the ingested dose or serum digoxin concentration, with a formula provided for calculation, as reported in Circulation 4
In critical cases requiring immediate treatment, empiric administration of 10-20 vials of digoxin-Fab is recommended, according to Circulation 4

The American College of Cardiology notes that digoxin concentration monitoring becomes unreliable after antidigoxin antibody administration 1
The response to digoxin-Fab is typically rapid, occurring within 30 minutes to 4 hours, as stated by the American College of Cardiology 1
Hemodialysis, hemofiltration, hemoperfusion, or plasmapheresis are not recommended for digoxin toxicity, according to Circulation 5

The American Heart Association gives a Class 1 (strongest) recommendation for administering digoxin-Fab in digoxin or digitoxin poisoning, representing the highest level of guideline support for any intervention in digoxin toxicity 6
Digoxin-Fab is a monovalent immunoglobulin that rapidly binds to intravascular digoxin, with clinical response rates of 80-90% in acute settings 7, 8
Dysrhythmia resolution typically occurs within 30-45 minutes of administration 6, 9
Each 40 mg vial binds approximately 0.5 mg of digoxin 7, 8
In observational studies of cardiac arrest from digoxin poisoning, survival was 54% (30 of 56 patients) with digoxin-Fab treatment 6

Atropine may be reasonable as a temporizing measure for bradydysrhythmias while awaiting digoxin-Fab administration, although evidence is limited to case reports with variable effects 6, 9, 10
Temporary cardiac pacing may be reasonable for refractory bradydysrhythmias, though complications are common (36% in one series) 6, 9
Lidocaine, phenytoin, or bretylium may be reasonable to treat ventricular dysrhythmias until digoxin-Fab can be administered 6, 9

The American Heart Association gives a Class 3 (harm/no benefit) recommendation against hemodialysis, hemofiltration, hemoperfusion, or plasmapheresis for digoxin removal 6, 9

Monitor potassium levels closely both before and after digoxin-Fab administration, as levels can shift dramatically 7, 8

Digoxin-Fab is also reasonable for poisoning from related cardiac glycosides including yellow oleander and Bufo toad venom, with similar efficacy demonstrated in observational studies 6, 9