DigiFab (Digibind) Dosing for Digoxin Poisoning

General:

• Acute, acute on chronic, or chronic digoxin toxicity.
• Poisoning with cardioactive steroid.

Specific indications:

• Any digoxin-related life-threatening dysrhythmia (independent of digoxin level).
• Potassium concentration >5 mEq/L in acute digoxin poisoning.
• Elevated serum digoxin level, chronic digoxin toxicity associated with dysrhythmias, significant gastrointestinal symptoms, or altered mental status.
• Serum digoxin level >15 ng/mL (19.2 nmol/L) at any time, or >10 ng/mL (12.8 nmol/L) 6-hours post-ingestion (independent of symptoms).
• Acute ingestion >10 mg digoxin in an adult.
• Acute ingestion >4 mg digoxin in a child.
• Poisoning with a non-digoxin cardioactive steroid (e.g. plants like foxglove and lily of the valley).

• Cardioactive steroid toxicity can cause nearly any dysrhythmia with the exception of a rapidly conducted supraventricular tachydysrhythmia.
• The serum digoxin level must be considered in the context of the patient’s clinical presentation; a reliable serum digoxin level must be obtained at steady-state (i.e., obtained ≥6 hours after ingestion). The serum digoxin level may be misleadingly high if obtained <6 hours after ingestion.
• Digoxin levels measured after administration of DigiFab will be falsely elevated. If required, free digoxin levels will need to be measured (not readily available at all labs).
• Hyperkalemia acts as a marker of poisoning severity in acute digoxin overdose. Correcting mild elevations in serum potassium without administering DigiFab will not improve survival (see Next Steps for details).
• Impaired creatinine clearance and aging (associated with decreased function of renal, hepatic, and cardiac systems) may result in clinical toxicity at lower serum digoxin levels.
• Electrolyte abnormalities (specifically hypokalemia, but including hypomagnesemia, hypercalcemia, hypernatremia) may result in dysrhythmias at lower serum digoxin levels.
• Drugs including quiNIDine, verapamil, dilTIAZem, carvedilol, amiodarone, and spironolactone will result in decreased digoxin protein binding, thereby increasing free digoxin levels.

Tips from the creator:

• The calculator is appropriate for vials containing (approximately) 40 mg of antibodies.
• Slow infusion (i.e., 2 hours) improves Fab efficacy. This way of infusion is preferable when rhythm disturbances are not life-threatening.
• In the case of chronic overdose, if digoxin level (in prehospital setting for example) is missing, a dose of 3 vials is appropriate (experience-based recommendation).

DigiFab is an effective antidote for acute, acute on chronic, and chronic digoxin toxicity. It is also indicated for poisoning from other cardioactive steroids.