Factor Xa Inhibitors

Chapter: Factor Xa Inhibitors
McMaster Section Editor(s): James Douketis
Section Editor(s) in Interna Szczeklika: Krystyna Zawilska†, Anetta Undas, Wiktoria Leśniak
McMaster Author(s): James Douketis
Author(s) in Interna Szczeklika: Anetta Undas, Krystyna Zawilska†
† Deceased.
Additional Information

1. Mechanism of action: Fondaparinux (subcutaneous or IV) is a synthetic pentasaccharide that binds only to antithrombin; rivaroxaban (oral), apixaban (oral), edoxaban (oral), and betrixaban (oral) cause factor Xa inhibition that is not mediated by antithrombin.

2. Monitoring of the anticoagulant effect is not necessary. However, within 2 to 4 hours of the administration of rivaroxaban, a prolonged prothrombin time (international normalized ratio [INR]) typically occurs (the effect is less pronounced after the administration of apixaban). Rivaroxaban, apixaban, and edoxaban have little or no effect on the activated partial thromboplastin time and thrombin time. In patients planned for urgent invasive procedures associated with a high risk of bleeding, the prothrombin time may be used to provide a crude estimate of the anticoagulant effect of rivaroxaban, edoxaban, and, to a lesser extent, apixaban. More reliable measures of the anticoagulant effects of rivaroxaban, apixaban, and edoxaban require the use of anti–factor Xa assays specific to these agents.

3. Contraindications are the same as with heparins and additionally include pregnancy and breastfeeding; do not use these agents in patients with creatinine clearance <15 mL/min, patients with severe liver failure, or in combination with other anticoagulants, dual antiplatelet therapy, thrombolytic agents, and drugs that can potentiate or impede the anticoagulant effect (eg, azole antifungal agents, and HIV protease inhibitors). Blood levels of rivaroxaban increase in patients receiving concomitant clarithromycin, erythromycin, cyclosporine (INN ciclosporin), tacrolimus, or fluconazole. Rifampin (INN rifampicin), phenobarbital, carbamazepine, phenytoin, and hypericum (St John’s wort) reduce the efficacy of rivaroxaban and apixaban.

4. Discontinuation of treatment before surgical procedures: see Perioperative Direct Oral Anticoagulant (DOAC) Management.

5. Complications: Mainly bleeding (in contrast to heparins, factor Xa inhibitors are not known to cause heparin-induced thrombocytopenia), allergic reactions. Andexanet-alpha is available is some jurisdictions to neutralize the anticoagulant effect but is expensive and not widely available. The anticoagulant effect of oral factor Xa inhibitors may be neutralized by a 4-factor prothrombin complex concentrate (PCC) 25 IU/kg (the dose may be repeated twice). The role of other prohemostatic agents, which include tranexamic acid, cryoprecipitate, and recombinant factor VII, in bleeding management is uncertain but can be considered in cases of bleeding that is refractory to administration of reversal agents. In addition, there is uncertainty about the potential prothrombotic effects of all prohemostatic agents in this clinical setting.

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