EINSTEIN Junior: Oral Rivaroxaban in Children With Venous Thrombosis

Inclusion Criteria: * Children aged birth to \< 18 years with confirmed venous thromboembolism who receive initial treatment with therapeutic dosages of UFH (unfractionated heparin), LMWH (low molecular weight heparin) or fondaparinux and require anticoagulant therapy for at least 90 days. However, children aged birth to \< 2 years with catheter-related thrombosis require anticoagulant therapy for at least 30 days. * For children younger than 6 months: * Gestational age at birth of at least 37 weeks. * Oral feeding/nasogastric/gastric feeding for at least 10 days. * Body weight ≥2600 g Exclusion Criteria: * Active bleeding or bleeding risk contraindicating anticoagulant therapy * An estimated glomerular filtration rate (eGFR) \< 30 mL/min/1.73 m\*2 (in children younger than 1 year, serum creatinine results above 97.5th percentile excludes participation) * 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 109/L * Sustained uncontrolled 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), including but not limited to all human immunodeficiency virus protease inhibitors and the following azole antimycotics agents: ketoconazole, itraconazole, …