Active pathological bleeding or patient at high risk for bleeding. Patients w/ prosthetic heart valve. Severe renal impairment. Concomitant use w/ antiplatelets, other anticoagulants, thrombolytics, dronedarone, P-glycoprotein inducers (e.g. carbamazepine, rifampicin, phenytoin and St John's wort) and P-glycoprotein strong inhibitors (e.g. ciclosporin, systemic ketoconazole, itraconazole, and tacrolimus).