EINSTEIN Junior Phase II: Oral Rivaroxaban in Young Children With Venous Thrombosis

Inclusion Criteria: * Children aged 6 months to \< 6 years who have been treated for at least 2 months or, in case of catheter related thrombosis, for at least 6 weeks with LMWH (low molecular weight heparin), fondaparinux and/or VKA (vitamin K antagonist) for documented symptomatic or asymptomatic venous thrombosis - Hemoglobin, platelets, creatinine, alanine aminotransferase (ALT) and bilirubin evaluated within 10 days prior to randomization * Informed consent provided Exclusion Criteria: * Active bleeding or high risk for bleeding contraindicating anticoagulant therapy * Symptomatic progression of venous thrombosis during preceding anticoagulant treatment * Planned invasive procedures, including lumbar puncture and removal of non peripherally placed central lines during study treatment * An estimated glomerular filtration rate (eGFR) \< 30 mL/min/1.73 m\^2 * Hepatic disease which is associated with either: coagulopathy leading to a clinically relevant bleeding risk, or ALT\> 5x upper level of normal (ULN) or total bilirubin \> 2x ULN with direct bilirubin \> 20% of the total * Platelet count \< 50 x 10\*9/L * Hypertension defined as \> 95th age percentile * Life expectancy \< 3 months * Concomitant use of strong inhibitors of both cytochrome P450 isoenzyme 3A4 (CYP3A4) and P-glycoprotein (P-gp), i.e. all human immunodeficiency virus protease inhibitors and the following azole antimycotics agents: ketoconazole, itraconazole, voriconazole, posaconazole, if used systemical…