Digoxin Overdose: Still No Role for Dialysis

The use of digoxin is not as common as it once was, but many prescribers still opt to manage patients with atrial fibrillation or heart failure with the cardiac glycoside.

While acute ingestion of a toxic dose of digoxin is rare, acute-on-chronic toxicity is more often observed. These patients may have experienced an acute kidney injury, drug interaction, or change in dosage that would cause this type of toxicity.

If the exposure is significant and signs and symptoms of digoxin toxicity are present, then digoxin immune fab (DigiFab) may be indicated. The signs and symptoms of chronic digoxin exposure warranting antidotal therapy include digoxin-associated dysrhythmias such as ventricular tachycardia/fibrillation and progressive bradydysrhythmias, as well as altered mental status.

When the acute-on-chronic toxicity is secondary to renal injury, some clinicians may consider hemodialysis to be effective at digoxin removal. However, most toxicologists would not routinely recommend this intervention.

A recent systematic review by the Extracorporeal Treatments in Poisoning working group analyzed the available evidence and arrived at the long-held conclusion that hemodialysis should not be routinely used in place of DigiFab. The study results further put to rest the misconception that hemodialysis may assist in clearance of the digoxin-fab complex, which it does not.

Hemodialysis is not effective for digoxin removal as a result of the tremendous tissue distribution of the drug at steady state, which is only approximately 0.5% in the blood.

Pharmacists who encounter this type of exposure and are involved with the dosing and monitoring of DigiFab should always calculate the dose, as the empiric dosing in the drug’s prescribing information is often too high for most cases. Following the recommended calculation based on the digoxin serum concentration and the patient’s weight is the best practice.

Also, keep in mind that DigiFab does not need a filter. DigiBind requires a 0.22-micron inline filter during administration, but DigiFAB does not.

In addition, don’t recheck a digoxin level. After administration of DigiBind, digoxin will be pulled from tissue into the plasma and form a complex with the fab. Since most laboratories only test total plasma digoxin levels, the result will represent both the free and bound digoxin.

In other words, it’s clinically useless. Free levels are available in some labs, but they are not often necessary.

Reference

Mowry JB, et al. Extracorporeal treatment for digoxin poisoning: systematic review and recommendations from the EXTRIP Workgroup. Clin Toxicol (Phila). 2016 Feb;54(2):103-114.