How Eliquis (Apixaban) Works
Eliquis (apixaban) works as a direct factor Xa inhibitor that selectively and reversibly inhibits both free and clot-bound factor Xa, preventing thrombin generation and thrombus development. 1
Mechanism of Action
Apixaban functions through a highly specific mechanism:
- It directly inhibits factor Xa without requiring antithrombin III for its anticoagulant activity 1
- It inhibits free factor Xa, clot-bound factor Xa, and prothrombinase activity 1, 2
- By inhibiting factor Xa, apixaban decreases thrombin generation, which prevents the conversion of fibrinogen to fibrin 3
- This action ultimately prevents thrombus formation and thrombin-induced platelet aggregation 3
Unlike warfarin, which affects multiple clotting factors, apixaban has a targeted mechanism that contributes to its more predictable anticoagulant effect.
Pharmacokinetic Properties
Apixaban has favorable pharmacokinetic characteristics:
- Oral bioavailability of approximately 50% 1, 2
- Rapid absorption with peak plasma concentrations occurring 3-4 hours after administration 1, 3
- Half-life of approximately 12 hours, allowing for twice-daily dosing 4, 2
- Multiple elimination pathways:
Clinical Implications
The pharmacological profile of apixaban offers several clinical advantages:
- Predictable anticoagulant effect without need for routine coagulation monitoring 2
- Fewer drug-drug interactions compared to warfarin 4
- Lower risk of intracranial hemorrhage compared to warfarin, particularly important in elderly patients 4
- Effective in patients with mild to moderate renal impairment 4
Laboratory Effects
Apixaban affects common coagulation tests, but these changes have limited clinical utility:
- Prolongs prothrombin time (PT), international normalized ratio (INR), and activated partial thromboplastin time (aPTT) 1
- These changes are small, variable, and not useful for monitoring anticoagulation effect 1
- Anti-factor Xa activity assays can measure apixaban effect but are not routinely recommended 1
Important Drug Interactions
Several factors can affect apixaban levels:
- Strong inhibitors of both CYP3A4 and P-glycoprotein (e.g., ketoconazole, ritonavir) are contraindicated as they significantly increase plasma concentrations 3
- Concurrent use of antiplatelet agents, NSAIDs, SSRIs, or SNRIs increases bleeding risk 4
- Apixaban is a substrate for P-glycoprotein (P-gp) transport system, which affects its absorption and elimination 3, 4
Clinical Applications
Apixaban has been approved for multiple indications:
- Prevention of venous thromboembolism (VTE) after hip or knee replacement surgery 3, 5
- Treatment of deep vein thrombosis (DVT) and pulmonary embolism (PE) 6
- Prevention of stroke and systemic embolism in patients with non-valvular atrial fibrillation 7
- Prevention of recurrent DVT and PE 6
The specific mechanism of action and favorable pharmacokinetic profile make apixaban an effective anticoagulant with a predictable effect and improved safety profile compared to traditional vitamin K antagonists.