Pharmacology · Anticoagulant reversal agents
Idarucizumab !
A humanised antibody fragment that grabs dabigatran and quickly switches off its effect, for urgent surgery or life-threatening bleeding.
Updated 2026-11-01
The figure shows dabigatran held by a mouse anti-dabigatran antibody fragment (Fab) from an antidote study; idarucizumab is a humanised Fab with the same purpose.
Mechanism of action
Idarucizumab is the Fab fragment of a humanised monoclonal antibody made against dabigatran. It binds dabigatran far more tightly than dabigatran binds thrombin, so it pulls the drug off thrombin and holds it in an essentially irreversible complex. Thrombin activity returns and clotting normalises quickly; the complex is cleared by the kidneys.
- Idarucizumab binds circulating dabigatran very tightly
- Dabigatran is pulled away from thrombin
- Clotting returns; the kidneys clear the complex
Pharmacokinetics
- Elimination
- Mainly through the kidneys.
- Half-life
- About 1 hour with normal kidney function.
- Onset and duration
- Rapid: the anticoagulant effect of dabigatran is reversed quickly after the infusion.
Indications
- Reversal of dabigatran before emergency surgery or urgent procedures. Anticoagulant poisoning (warfarin and superwarfarins) →
- Life-threatening or uncontrolled bleeding in a patient taking dabigatran, such as intracranial bleeding. Intracerebral haemorrhage →
Adverse effects
Common
- Return of the clotting risk for which dabigatran was given once its effect is removed
Contraindications
- Not used outside life-threatening bleeding or urgent surgery: reversal removes protection against clots
Key interactions
- Dabigatran
- Binds and neutralises it; it does not reverse factor Xa inhibitors, heparins or warfarin.
- Restarting anticoagulation
- Dabigatran or another anticoagulant can be restarted once bleeding is controlled, as the team decides.
What is monitored
- Coagulation tests sensitive to dabigatran (aPTT, thrombin time) before and after
- Bleeding control and haemoglobin
- Kidney function, which affects how long dabigatran lingers
- Signs of new thrombosis after reversal
Administration and safety
- Intravenous, as two consecutive boluses, without delay
- A second course may be considered if bleeding recurs with persistent dabigatran effect
- Anticoagulation is restarted when safe, because the patient's clotting risk remains
Nursing care
- Confirm that the patient takes dabigatran and record the time of the last dose
- Draw coagulation tests before and after the infusion
- Watch bleeding sites and vital signs closely
- Look out for signs of new clots (leg swelling, chest pain, stroke signs) after reversal
Pregnancy and breastfeeding
Information in pregnancy is limited; it is used when the mother's life-threatening bleeding requires it.
Test yourself
Think of the answer, then tap the question to see it.
What kind of molecule is idarucizumab, and what does it bind?
A humanised monoclonal antibody Fab fragment that binds dabigatran.
Does idarucizumab reverse apixaban or rivaroxaban?
No. It is specific to dabigatran; andexanet alfa is the antidote for the factor Xa inhibitors.
Why is idarucizumab reserved for life-threatening bleeding or urgent surgery?
Reversing dabigatran exposes the patient again to the thrombotic disease for which the anticoagulant was given.
Related drugs
Related conditions
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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: 4JN2: An Antidote for Dabigatran (RCSB Protein Data Bank, 2013); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 36 (McGraw Hill, 2023); Farmacología básica y clínica (Katzung), cap. 34 (McGraw Hill, 2025).
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Representative model, for educational purposes only.