Andexanet Alfa

How it works

Acting as a high-affinity decoy, it binds factor Xa inhibitor molecules and neutralises their activity, allowing endogenous factor Xa to resume thrombin generation and restore haemostasis.

Prescribing in practice

• There is a recognised risk of thromboembolic and ischaemic events following reversal, so use should be restricted to serious bleeding and anticoagulation reinstated as soon as it is clinically safe.
• Administration is a bolus then a continuous infusion, with low- or high-dose regimens chosen by the offending agent, its last dose and timing.
• Anti-factor Xa activity assays are unreliable for monitoring during and shortly after treatment and should not guide management.

Monitoring

Observe closely for recurrent bleeding and for symptoms or signs of arterial or venous thrombosis after dosing.

Counselling the patient

• It is an injectable treatment given in hospital for severe bleeding.
• Tell staff about any signs of a new clot, such as chest pain, breathlessness or limb swelling.
• The team will decide when it is safe to restart your usual blood thinner.

Evidence & guidelines

Evidence from the ANNEXA-4 study underpins its licensed use as a specific factor Xa inhibitor reversal agent, with NICE and MHRA guidance applying.