Antidote Pregnancy: C - use if benefits outweigh risks; digoxin toxicity itself is life-threatening

Digoxin-specific Antibody Fragments (DigiFab)

Brand names: DigiFab, Digibind

Adult dose

Dose: Empirical: 10 vials IV; Calculated: vials = [serum digoxin (ng/mL) x weight (kg)] / 100

Route: IV

Frequency: Single infusion over 30 min (cardiac arrest: bolus)

Each vial (40 mg) binds ~0.5 mg digoxin. Empirical 10 vials covers most acute overdoses. For chronic toxicity, 3-6 vials may suffice. Serum digoxin levels unreliable for 6-8 h after administration.

Paediatric dose

Route: IV

Frequency: Single infusion over 30 min

Max: Calculated same as adult; for small children monitor for fluid overload

Same calculation. For infants and small children, reconstitute 1 vial in 36 mL saline (1 mg/mL) to allow accurate dosing.

Dose adjustments

Renal

No dose adjustment required; however, re-bound toxicity may occur in renal failure - monitor for 2-4 days.

Clinical pearls

Indications: life-threatening arrhythmia (VT, VF, complete heart block), hyperkalaemia >5 mmol/L, digoxin level >10 ng/mL, acute ingestion >10 mg adult / >4 mg child.
Hyperkalaemia in digoxin toxicity is a marker of severity - do NOT treat with calcium (risk of stone heart); treat the toxicity with DigiFab.
After DigiFab, total serum digoxin levels remain high (bound fragments) but are non-toxic. Only free digoxin level is meaningful.
Expect response within 20-60 min. Repeat dose if partial response at 30 min.
Rebound toxicity in renal failure: fragments may be reabsorbed as kidneys fail to excrete - may require repeat dosing or dialysis.

Contraindications

Known hypersensitivity to ovine proteins (sheep-derived) - consider skin test if time allows
Cardiac failure solely dependent on digoxin for inotropic support (relative)

Side effects

Re-emergence of atrial fibrillation (removes digoxin rate control)
Hypokalaemia (unmasked after toxicity reversal)
Worsening heart failure in digoxin-dependent patients
Rapid ventricular rate in AF after reversal

Interactions

Serum digoxin assay: falsely elevated for 6-8 h post-dose - use free digoxin assay if available
Hypokalaemia drugs: monitor potassium closely after reversal

Monitoring

Continuous ECG
Serum potassium (hypokalaemia common post-reversal)
Heart rate / rhythm
Signs of re-bound toxicity at 4-8 h

Reference: BNFc; UK Toxbase; NPIS Clinical Toxicology 2023; BNF 84; ERC Resuscitation Guidelines 2021. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways