Factor Xa inhibitor antidote

Synonyms and keywords: Factor Xa inhibitor antidote, factor Xa inhibitor reversal agent, FXa inhibitor antidote, Factor 10a inhibitor antidote

Overview
Direct Factor Xa inhibitors include Rivaroxaban, Betrixaban, Apixaban and Edoxaban. These agents bind directly to a serine residue of Factor Xa and inhibit the ability of Factor Xa to bind to the active site. They work by steric hinderance. They bind reversibly. Thus there is an equilibrium where these inhibitor molecules are binding and falling off of the Factor Xa molecule. Indirect inhibitors like fondaparinux and enoxaperin require antithrombin 3 (AT3) in addition.

Mechanism of Action
This is a "decoy" mechanism whereby the antidote binds to the Factor Xa inhibitor and soaks it up so it doesn’t bind and inhibit the Factor Xa. The binding to the Factor Xa inhibitor is reversible. The avidity of the binding is about the same as the avidity with which the Factor Xa inhibitor binds to the Factor Xa molecule. The antidote soaks up or binds all of the Factor Xa inhibitor by binding to it. As a Factor Xa inhibitor falls off of the Factor Xa molecule, it gets soaked up or bound to the antidote. The antidote does not appear to be procoagulant or anticoagulant.