**6. Rivaroxaban (Xarelto)**

#### **6.1 Mechanism of action**

Rivaroxaban is a factor Xa inhibitor that blocks the active site of factor Xa as well as prothrombinase activity and clot-associated factor Xa [20]. It also inhibits thrombin generation. The drug's half-life is 6–7 hours.

Rivaroxaban can lead to prolonged PT and activated partial thromboplastin time (aPTT), but it has no effect on thrombin and antithrombin activity.

It does not require routine monitoring of coagulation, but it may need anti–factor Xa chromogenic and PT assay to quantify its plasma level. However, it does require periodic assessment of renal function.

There are limited data on the drug's use in children 1 year or age or older with moderate-to-severe renal impairment. There is also no clinical data available in pediatric patients younger than 1 years old with serum creatinine above the 97.5th percentile. This drug is not recommended for use in children younger than 6 months.

#### **6.2 Other drugs**

Fetal hemoglobin-inducing agents [3, 21] like hydroxycarbamide and decitabine also appear to reduce plasma markers of thrombin formation. Hydroxycarbamide may change hypercoagulability in many ways; it may lower phospholipid expression on the surface of RBCs and platelets, and it reduces RBC adhesion to thrombospondin, a thrombin-sensitive protein. It may also reduce white blood cell (WBC) count, especially monocytes expressing transcription factor.

Hydroxyurea is a hemoglobin F stimulating agent. It increases hemoglobin F and improves the clinical symptoms of β-thalassemia disease and reduces hypercoagulability state due to decreased exposure of phosphatidylserine on the membranes of RBCs [2, 21].
