Pharmacology · Anticoagulant reversal agents

Andexanet alfa !

An inactive decoy copy of factor Xa that soaks up apixaban or rivaroxaban, used when they cause life-threatening bleeding.

Updated 2026-11-01

Class: Anticoagulant reversal agents
Target: Factor Xa inhibitors (apixaban, rivaroxaban), which it captures
ATC code: V03AB38

Also called: coagulation factor Xa (recombinant), inactivated

Factor Xa inhibitors (apixaban, rivaroxaban), which it capturesAndexanet alfa

The figure shows normal human factor Xa with apixaban in its active site; andexanet is a modified factor Xa that holds the drug in this same pocket but cannot clot.

Target in 3D: Factor Xa inhibitors (apixaban, rivaroxaban), which it captures. PDB structure 2P16 (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

Andexanet is a recombinant factor Xa in which the active-site serine has been replaced by alanine, so it has no clotting activity, and the Gla domain has been removed, so it cannot join the prothrombinase complex. It still binds factor Xa inhibitors in its active site. Given in large amounts, it sequesters apixaban or rivaroxaban, the patient's own factor Xa is freed, and thrombin generation recovers.

Andexanet is a factor Xa copy with no catalytic activity
Apixaban or rivaroxaban binds andexanet instead of real Xa
The patient's own Xa works again and thrombin generation recovers

Pharmacokinetics

Onset and duration: Rapid: anti-Xa activity falls quickly after the intravenous bolus, which is followed by an infusion over about two hours.

Indications

Life-threatening or uncontrolled bleeding in patients taking apixaban or rivaroxaban, especially intracranial bleeding. Intracerebral haemorrhage →
Reversal of factor Xa inhibitor effect in serious bleeding. Anticoagulant poisoning (warfarin and superwarfarins) →

Adverse effects

Common

Thrombotic complications after reversal

Contraindications

Procedures where heparin is routinely used, such as cardiac or vascular surgery, because andexanet also reverses heparin
Not evaluated for reversal before urgent surgery

Key interactions

Heparin and low-molecular-weight heparins: Andexanet also reverses them, which can defeat planned heparin anticoagulation.
Apixaban and rivaroxaban: Binds and neutralises them; higher amounts are needed for rivaroxaban than for apixaban.

What is monitored

Bleeding control and haemoglobin
Signs of thrombosis, stroke, heart attack or cardiac arrest after the infusion
Timing of the last apixaban or rivaroxaban dose, which sets the regimen

Administration and safety

Intravenous bolus followed by an infusion of about two hours
The regimen depends on which factor Xa inhibitor was taken, its dose and the time since the last dose
Restarting anticoagulation is planned as soon as it is safe
If it is unavailable, four-factor prothrombin complex concentrate is an alternative

Nursing care

Record which factor Xa inhibitor was taken and when
Monitor vital signs and neurological status closely during and after the infusion
Watch for new clots: chest pain, leg swelling, stroke signs
Do not give it before cardiac or vascular surgery where heparin will be used, unless the team decides so

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.

How is andexanet different from normal factor Xa?

Its active-site serine is replaced by alanine, so it has no clotting activity, and its Gla domain is removed, so it cannot join prothrombinase; it still binds factor Xa inhibitors.

Which anticoagulants does andexanet reverse?

Apixaban and rivaroxaban (factor Xa inhibitors); it also reverses heparin and low-molecular-weight heparins.

What serious adverse events have been reported after andexanet?

Thrombotic complications, cardiac arrest and sudden death.

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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: ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026); 2P16: Factor Xa in Complex with the Inhibitor APIXABAN (BMS-562247) (RCSB Protein Data Bank, 2007); 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.