Andexanet Alfa

How it works

It is a catalytically inactive factor Xa analogue that binds and sequesters factor Xa inhibitors, removing their anticoagulant effect and restoring endogenous thrombin generation.

Prescribing in practice

• Thromboembolic events — including arterial and venous thrombosis, ischaemic stroke and cardiac arrest — have been reported after use, so it must be reserved for serious bleeding and resumption of anticoagulation considered once clinically appropriate.
• It is given as a bolus followed by a continuous infusion, with the regimen selected according to the specific factor Xa inhibitor, its dose and the time since the last dose.
• It is not indicated for reversal of direct thrombin inhibitors and has limited supporting data for agents other than apixaban and rivaroxaban.

Monitoring

Monitor for re-bleeding and for clinical signs of thromboembolism after administration, alongside standard haemodynamic observation.

Counselling the patient

• This is an emergency hospital treatment used to stop serious bleeding.
• The care team will weigh up the risk of new clots and restart anticoagulation when it is safe.
• Routine clotting blood tests do not reliably reflect how well it is working.

Evidence & guidelines

Andexanet alfa is the licensed specific reversal agent for factor Xa inhibitors, supported by the ANNEXA-4 study and reviewed by NICE/MHRA.