News

Digoxin antibody fragments (Fab) (Digifab) Intravenous for Adults

Who can administer

May be administered by registered competent doctor or nurse/midwife

Important information

  • Once Digifab has been administered, there is no clinical benefit in measuring serum digoxin levels (as the level will represent both free and bound digoxin.)

    • Therefore, it is important to monitor the cardiac status of the patient for at least 24 hours after administration for signs of recurrent toxicity (ref 1)
  • Infusion related reactions or hypersensitivity reactions are possible - monitor closely for signs of allergic reaction. See Further Information
  • Consultation with National Poisons Centre (NPIC) may be advisable in acute overdose situation or if clinical features persist despite treatment (ref 1)
  • The onset of response is usually within 30 minutes
  • See also Renal impairment below
  • See 'Monitoring'overleaf
  • Stored in fridge in ED with back-up stock in the pharmacy

Available preparations

Digifab 40mg vial

Reconstitution

Water for injection

4ml per 40mg vial

Infusion fluids

Sodium chloride 0.9%

Methods of intravenous administration

Intermittent intravenous infusion (preferred route)

  • Dilute required dose with any convenient volume of infusion fluid (suggested volume 100ml (ref 2)) and administer over 30 minutes
  • If an infusion related reaction occurs, the infusion should be stopped and the patient treated. Consider restarting the infusion at a slower rate (ref 1,2)
  • The residual volume in the infusion line must be flushed through at the same rate to avoid significant underdosing

Bolus intravenous injection

  • If cardiac arrest is imminent Digifab may be given undiluted by rapid injection (ref 2)
  • An increased incidence of allergic reactions may be expected using a bolus intravenous injection

Dose in adults

A: Cardiac arrest due to digoxin toxicity:

  • Urgently administer Digifab as an IV bolus
  • Weight greater than 40kg: give 5 vials (200 mg)
  • Further doses may be required if an adequate clinical response is not seen after 30 minutes

B: Other indications

  • e.g.acute digoxin overdose on top of usual therapy, acute overdose in digoxin-naive patient, digoxin toxicity from chronic therapy - the following calculations can be used to work out the required dose
  • Doses below are as per Toxbase, rather than the SPC
  • If clinical features persist despite treatment, discuss with Posions centre

The dose depends on the clinical situation and on whether plasma digoxin concentration is available (ref 1)

    • B1. When digoxin concentration is available (measured 6 hours after overdose/last dose, unless urgently indicated in patient with arrhythmia):

      • Number of vials =

        • {0.781 x serum digoxin concentration (nanomol/L) x weight (kg)} /200
      • Round up to the nearest vial - for convenience, these doses have been worked out in table 1 below
    Table 1: Initial dose - when digoxin concentration is available
    • As most assay kits are not designed to measure values above 6.4nmol/L (5ng/ml),serum digoxin concentration reported may be inaccurate at high levels
    • Important: If clinical features persist despite initial dose, then discuss with NPIC (01) 809 2566 or 01 837 9964

    Example, a patient who weighs 80kg, with a digoxin level of 5.12nanomoL/L- should receive an initial dose of 2 vials

    Patient weight (kg) Serum digoxin concentration (nanomol/L)
      2.56 5.12 10.24 15.36 20.48 25.6
    40 1 vial 1 vial 2 vials 3 vials 4 vials 4 vials
    60 1 vial 2 vials 3 vials 4 vials 5 vials 6 vials
    70 1 vial 2 vials 3 vials 5 vials 6 vials 7 vials
    80 1 vial 2 vials 4 vials 5 vials 7 vials 8 vials
    100 1 vial 2 vials 4 vials 6 vials 8 vials 10 vials
    • B2. When only ingested dose is available (overdose situation):

      • Number of vials = Amount of digoxin ingested (mg) x 0.8
      • Round up to the nearest vial
      • If clinical features persist despite initial dose, then discuss with NPIC (01) 809 2566 or 01 837 9964
      • Example: if a patient ingested twenty-five tablets of the 0.25mg strength, as an acute single ingestion, (0.25mg x 25 tablets x 0.8) = 5 vials initially

    Renal impairment

    • It may be expected that excretion of the Fab-digoxin levels complexes from the body is slowed in the presence of renal impairment, and that digoxin may be released after some days from retained Fab-digoxin complexes

    General information

    • Erroneous dosage calculations may result from inaccurate estimates of the amount of digoxin ingested or absorbed, or from non steady-state serum digoxin concentrations
    • If after several hours toxicity has not been adequately reversed or appears to recur, re-administration of Digifab at a dose guided by clinical judgement may be required
    • If there is no response to an adequate dose of Digifab, the diagnosis of digitalis toxicity should be questioned

    Monitoring

    • Patients should have continuous ECG monitoring during and for at least 24 hours after administration of Digifab
    • Monitor temperature, potassium, blood pressure during and after administration

    Further information

    • Digoxin serum levels are reported in UHG as nanomol/l. Toxbase refers to levels in nanogram/ml
    • To convert nanomol/L to nanogram/ml multiply nanomol/L by 0.781. For example 2.5 nanomol/L = 1.95nanogram/ml
    • The likelihood of hypersensitivity reactions is higher in patients who are allergic to sheep-derived proteins, or to papain, an extract of the papaya fruit, dust mites or latex
    • Digoxin antidote has previously been used in two doses: one calculated to neutralise all the digoxin load ('full neutralisation' dose (FND)) and one calculated to neutralise only half of it ('half neutralisation' dose)
      • Recent evidence indicates that the 'half neutralisation' dose is adequate for most patients.
      • The dosage information in this monograph is taken from Toxbase. It recommends the use of 'Half-neutralisation doses'.

    Storage

    • Store at 2 to 80C
    • Do not freeze

    References

    Package insert and SPC June 2024

    1: Toxbase, downloaded 10/04/2025

    2:Injectable Medicines Administration Guide Medusa downloaded 10/04/2025

    Therapeutic classification

    Antidote

    IV Guide Type