Direct Fаctоr Xа Inhibitоrs Rivаrоxaban (Xarelto) Apixaban (Eliquis) Edoxaban (Savaysa) Mechanism of Action Directly inhibit Factor Xa (free + clot-bound) Block conversion: prothrombin → thrombin ↓ fibrin clot formation Pharmacokinetics Oral agents Onset: ~2–4 hours Duration: ~12 hours (varies) Hepatic metabolism (CYP3A4: rivaroxaban, apixaban) P-gp substrate → drug interactions Renal excretion → dose adjust in renal impairment Contraindicated: pregnancy, severe renal dysfunction Rivaroxaban taken with food Pharmacodynamics No routine monitoring required Rapid anticoagulant effect Predictable dose-response Reversal agent: Andexanet alfa Indications VTE treatment and prevention (DVT, PE) Stroke prevention in non-valvular AFib ACS/IHD risk reduction (selected cases) Heparin-induced thrombocytopenia (HIT) alternative (no PF4 interaction) Adverse Effects Bleeding (rivaroxaban highest risk among Xa inhibitors) Epidural/spinal hematoma → boxed warning Thrombotic events if abruptly stopped → boxed warning Edoxaban: ↑ ischemic stroke risk in non-valvular AFib → boxed warning Contraindications & Interactions Liver dysfunction (rivaroxaban, apixaban contraindicated) Moderate–severe hepatic impairment (edoxaban contraindicated) Strong CYP3A4 + P-gp inhibitors/inducers alter levels Monitoring No routine coagulation monitoring required Assess renal function periodically Monitor for bleeding signs Question: A 72-year-old man with nonvalvular atrial fibrillation is being evaluated for long-term stroke prevention. His past medical history is significant for hypertension and chronic kidney disease. Laboratory studies show a creatinine clearance of 18 mL/min (normal: >90 mL/min). Liver function tests are within normal limits. He is started on an anticoagulant. Which of the following is the most appropriate anticoagulation therapy for this patient?