PK of Rivaroxaban in Bariatric Patients - Extension

Inclusion Criteria: * Patient with past elective bariatric surgery (Roux-en-Y gastric bypass surgery or sleeve gastrectomy 6-8 months ago) * Patient aged 18 years and older * BMI ≥ 35 kg/m2 * Women of child-bearing age: Willingness of using a double barrier contraception method during the study * Written, informed consent Exclusion Criteria: * Intake of oral anticoagulants (phenprocoumon, acenocoumarol, dabigatran, etexilate, apixaban etc.) 4 weeks prior to inclusion in the study * Application of parenteral anticoagulants (unfractionated heparin, low molecular weight heparins, heparin derivates (fondaparinux etc.) 4 weeks prior to inclusion in the study * Pharmacologic platelet inhibition 4 weeks prior to inclusion in the study * Known coagulation disorders (e.g. Willebrand's disease, haemophilia) * Evidence for deep vein thrombosis or pulmonary embolism in the personal history or in the history of first degree relatives * Medical condition that is associated with an increased risk for VTE, i.e. active cancer disease, lupus erythematodes chronic inflammatory bowel disease * Active, clinically significant bleeding * Congenital or acquired bleeding disorder * Uncontrolled severe hypertension * Active gastrointestinal disease that can potentially lead to bleeding disorder: oesophagitis, gastritis, gastroesophageal reflux disease, chronic inflammatory bowel disease * Vascular retinopathy * Bronchiectasis or history of pulmonary bleeding * Prior stroke or TIA * Hereditary galactose intolerance, Lapp lactase deficiency, glucose-lactose malabsorption * Severe renal impairment with a creatinine clearance (GFR) of \< 30ml/min * Positive pregnancy test, pregnancy or nursing women * High risk of bleeding (e.g. active ulcerative gastrointestinal disease) * Known intolerance of the study medication rivaroxaban * Concomitant treatment with strong CYP3A4 inhibitors (e.g. ketoconazole, itraconazole, lopinavir, ritonavir, indinavir) * Concomitant treatment with an P-glycoprotein inhibitor and weak or moderate CYP3A4 inhibitor (e.g. erythromycin, azithromycin, diltiazem, verapamil, quinidine, ranolazine, dronedarone, amiodarone, felodipine)