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# Digoxin immune Fab

Antibody fragments made in sheep that bind digoxin in the blood and pull it off the sodium pump. The specific antidote for severe digoxin poisoning.

Updated 2026-11-01

- Class: [Specific antidotes](https://durgical.com/en/pharmacology/classes/specific-antidotes/)
- Target: Digoxin itself (and other cardiac glycosides)
- ATC code: V03AB24

Also called: Digoxin-specific antibody fragments, digitalis antitoxin

◆**Digoxin itself (and other cardiac glycosides)**Digoxin immune Fab

ⓘ The figure shows digoxin held by the Fab of the mouse monoclonal antibody 26-10; the antidote is a different, sheep-derived Fab with the same idea.

**Target in 3D:** Digoxin itself (and other cardiac glycosides). PDB structure 1IGJ (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/1IGJ) · Drag to rotate · pinch to zoom

## Mechanism of action

The Fab fragments bind free digoxin with an affinity higher than the drug's own affinity for the Na⁺/K⁺-ATPase. Free digoxin falls, digoxin leaves the pump, and the pump works again: arrhythmias settle and potassium moves back into cells. The digoxin–Fab complex is then cleared by the kidneys.

- Fab binds free digoxin in the blood
- Digoxin comes off the Na⁺/K⁺ pump
- The pump restarts: rhythm improves, K⁺ re-enters cells
- The kidneys clear the digoxin–Fab complex

## Pharmacokinetics

**Distribution**
Mostly in the blood and extracellular space

**Elimination**
By the kidneys together with the bound digoxin; slower in kidney failure, when toxicity can recur

**Onset and duration**
Symptoms usually improve within 30 to 60 minutes

## Indications

- Life-threatening arrhythmias from digoxin (ventricular arrhythmias, progressive bradycardia, high-grade AV block), whatever the serum level
- Severe hyperkalaemia in acute digoxin poisoning
- Poisoning by other cardiac glycosides, such as digitoxin or oleander, though cross-reactivity is incomplete

## Adverse effects

### Common

- Worsening heart failure as digoxin's inotropic effect is lost
- Hypokalaemia, often within hours

### Serious (rare, important)

- Anaphylaxis, more likely with allergy to sheep proteins
- Serum sickness days after treatment

## Contraindications

- No absolute contraindications; allergy to sheep proteins is a relative contraindication

## Key interactions

**Potassium replacement**
Potassium can fall quickly once the pump restarts, so it is replaced only as needed

## What is monitored

- Continuous ECG
- Serum potassium, frequently in the first hours
- Kidney function
- Signs of heart failure and ventricular rate

## Administration and safety

- Reconstituted and given intravenously, usually as an infusion; as a bolus in imminent cardiac arrest
- The amount is calculated from the dose ingested or the serum level; the number of vials is checked twice
- A serum digoxin sample is drawn before the first dose

## Nursing care

- Draw digoxin and potassium levels before giving it
- Keep the patient on cardiac monitoring with resuscitation equipment at hand
- Ask about allergy to sheep proteins
- Teach the patient to report rash, fever or joint pain in the following days

## Memory aid

Fab = Fetch And Bind: it fetches digoxin off the pump, binds it in the blood, and the kidneys carry the pair away (watch potassium drop).

## Test yourself

Think of the answer, then tap the question to see it.

## How does digoxin immune Fab reverse toxicity?

It binds free digoxin more tightly than the Na⁺/K⁺-ATPase does, so digoxin leaves the pump.

## Why can potassium fall after the antidote?

The pump restarts and moves potassium back into cells.

## Can digoxin Fab help in poisoning by plant cardiac glycosides?

Yes, it can be tried (for example oleander), but cross-reactivity is incomplete and more may be needed.

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## Related drugs

- [Digoxin](https://durgical.com/en/pharmacology/digoxin/)

[← Back to the class: Specific antidotes](https://durgical.com/en/pharmacology/classes/specific-antidotes/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [Guía para el Manejo de Emergencias Toxicológicas](https://minsalud.gov.co/sites/rid/Lists/BibliotecaDigital/RIDE/DE/GT/guias-manejo-emergencias-toxicologicas-outpout.pdf) (Ministerio de Salud y Protección Social; Organización Panamericana de la Salud, 2017); Farmacología básica y clínica (Katzung), 16.ª ed., cap. 58 (McGraw Hill, 2025); [DailyMed - DIGOXIN tablet](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=f3d29508-e7cc-47ff-845d-b5375ee30407) (DailyMed (U.S. National Library of Medicine), 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=V03AB24) (WHO Collaborating Centre for Drug Statistics Methodology, 2026); [RCSB PDB - 1IGJ: 26-10 FAB:DIGOXIN COMPLEX-AFFINITY AND SPECIFICITY DUE TO SURFACE COMPLEMENTARITY](https://www.rcsb.org/structure/1IGJ) (RCSB Protein Data Bank, 2026).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/digoxin-immune-fab/