Andexanet alfa is used to reverse which anticoagulants, and what is its mechanism?
- A Reverses direct Factor Xa inhibitors (rivaroxaban, apixaban) by acting as a decoy Xa molecule that binds and sequesters them ✓
- B Reverses dabigatran by competitively binding its active site; does not reverse rivaroxaban
- C Reverses all DOACs by activating Protein C pathway to restore coagulation
- D Reverses rivaroxaban by inhibiting CYP3A4, reducing plasma rivaroxaban levels
Correct answer: A. Reverses direct Factor Xa inhibitors (rivaroxaban, apixaban) by acting as a decoy Xa molecule that binds and sequesters them
Explanation
Andexanet alfa is a modified recombinant Factor Xa molecule that lacks the gamma-carboxyglutamic acid (Gla) domain (cannot assemble into the prothrombinase complex) and has an active site mutation reducing catalytic activity. It acts as a decoy Xa to bind and sequester direct Factor Xa inhibitors (rivaroxaban, apixaban, edoxaban, betrixaban) with high affinity, rapidly reversing their anticoagulant effect. It does NOT reverse direct thrombin inhibitors (dabigatran) — idarucizumab is used for dabigatran reversal.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
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