This study aims to determine the effects of end-stage renal disease on the pharmacokinetics, pharmacodynamics, safety, and tolerability of apixaban. This is a single-center open-label pharmacological study. Apixaban will be prescribed at the dose of 2.5 mg twice per day for nine days. The concentration of the drug will be measured with repetitive blood tests the first and the eighth day of administration (non-dialysis days). The same blood tests will be repeated before, during, and after dialysis on dialysis days. If the study shows inadequate or suboptimal efficacy with the 2.5 mg dose, it will be repeated with the 5 mg twice-daily dose.

Inclusion Criteria:

• age>18 years
• end-stage renal disease on stable hemodialysis treatment (3 weekly sessions of 4 hours) for at least 6 months
• no residual kidney function
• non-valvular atrial fibrillation

Exclusion Criteria:

• age ≥80 years
• Body mass index (BMI)<21 or BMI>40
• active bleeding
• high bleeding risk (HAS BLED score >3)
• active malignancy
• psychiatric disorders
• decompensated thyroid disorders
• decompensated heart failure
• acute myocardial infarction-cerebrovascular accident-head trauma in the last 3 months
• previous history of venous thromboembolic disease in the last 6 months
• previous history of coagulopathy already treated by vitamin K antagonists (VKAs) or novel oral anticoagulants
• uncorrected rhythm or conduction disturbances
• dual antiplatelet therapy
• known liver disease or elevated transaminases > 2x upper limit of normal
• Hemoglobin < 90 g/l
• platelets < 100,000 /ml
• known hypersensitivity to apixaban
• treatment with a potent inhibitor or inducer of the cytochrome P450 3A4 and/or P-glycoprotein
• absence of effective contraception where applicable
• drug or alcohol abuse