Thromboembolism

Inclusion Criteria

- Children from birth to less than 6 months with documented symptomatic or asymptomatic venous or arterial thrombosis who have been treated with anticoagulant therapy for at least 5 days. 
 - Gestational age at birth of at least 37 weeks.
 - Hemoglobin, platelets, creatinine, ALT and total and direct bilirubin assessed within 10 days prior to enrollment.
 - Oral feeding/nasogastric/gastric feeding for at least 10 days.
 - Informed consent provided.
 - Body weight >2600 g

Exclusion Criteria

- Active bleeding or high risk for bleeding 
 contraindicating anticoagulant therapy, including history of intra-ventricular bleeding.
 - Symptomatic progression of thrombosis during preceding anticoagulant treatment.
 - Planned invasive procedures, including lumbar puncture and removal of non-peripherally placed central lines during study treatment.
 -  Hepatic disease which is associated with either: coagulopathy leading to a clinically
relevant bleeding risk, or alanine aminotransferase (ALT) > 5x upper level of normal (ULN) or total bilirubin (TB) > 2x ULN with direct bilirubin > 20% of the total.
 - Creatinine >1.5 times of normal.
 - Uncontrolled Hypertension defined as >95th percentile.
 - History of gastrointestinal disease or surgery associated with impaired absorption.
 - Platelet count <100 x 109/L.
 - Concomitant use of strong inhibitors of both cytochrome P450 isoenzyme 3A4 (CYP3A4) and P-glycoprotein (P-gp), e.g. all human immunodeficiency virus protease inhibitors and the following azole-antimycotics agents: ketoconazole, itraconazole, voriconazole, posaconazole, if used systemically (fluconazole is allowed)
 - Concomitant use of strong inducers of CYP3A4, e.g. rifampicin, rifabutin, phenobarbital, phenytoin and carbamazepine 
 -  Indication for anticoagulant therapy other than current thrombosis.
 - Indication for antiplatelet therapy or non-steroid anti-inflammatory drug (NSAID) therapy. Incidental use is allowed.
 -  Hypersensitivity to rivaroxaban or its excipients.
 -  Participation in a study with an investigational drug or medical device within 30 days prior to enrollment.