Which medications in the drug class Antidotes are used in the treatment of Third-Degree Atrioventricular Block (Complete Heart Block)?

Updated: Jul 05, 2018
  • Author: Akanksha Agrawal, MBBS; Chief Editor: Jeffrey N Rottman, MD  more...
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Antidotes are used in select cases for patients with third-degree AV block secondary to digoxin toxicity. These patients should receive a digoxin-specific antidote.

Digoxin immune Fab (DigiFab)

Digoxin immune Fab is an immunoglobulin fragment with a specific and high affinity for both digoxin and digitoxin molecules. It removes digoxin or digitoxin molecules from tissue-binding sites. Each vial contains 40 mg of purified digoxin-specific antibody fragments, which will bind approximately 0.6 mg of digoxin or digitoxin.

The dose of the antidote depends on the total body load (TBL) of digoxin. The digoxin TBL can be estimated in the following 3 ways:

1. Estimate the quantity of digoxin ingested in the acute ingestion, and assume 80% bioavailability for digoxin or 100% for digitoxin (X mg ingested × 0.8 = TBL)

2. Obtain a serum digoxin concentration (in ng/mL) and multiply it by the patient's weight in kilograms. Divide the result by 100 [number of vials = (digoxin concentration) x (patient's weight) / 100]

3. Use an empiric dose based on average requirements for an acute or chronic overdose in an adult or child

If the quantity of ingestion cannot be estimated reliably, the antidote may be administered empirically (it is safest to use the largest calculated estimate). Alternatively, be prepared to increase dosing if resolution is incomplete.

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