**3. Antithrombotic agents**

### **3.1 Antiplatelets**

Acetylsalicylic acid (2–5 mg/kg/day) is the most important treatment for the prevention and management of thromboembolism in β-thalassemia patients, especially those who have undergone splenectomy and who have thrombocytosis (platelet count greater than 500,000/mm3 ) [2]. Resistance to acetyl salicylic acid has been reported in some thalassemia patients, especially after spleen removal [2].

### **3.2 Anticoagulants**

Anticoagulants are used to reduce risk of embolism, halt clot extension, and prevent recurrence [1, 17].

### **3.3 Anticoagulants for acute PVT**

There is no randomized controlled trial regarding the use of anticoagulants in acute PVT. After 6 months of therapy, a complete recanalization has been reported in about 50% of patients, with good results in the case mesenteric vein involvement and a low incidence of complications. In contrast, there was 10% of cases of PVT which are resistant to anticoagulants [10].

Better outcomes are achieved in acute PVT when anticoagulants are given as early as possible. Rate of recanalization is about 69% if treatment is started within the first week after diagnosis. Rate of recanalization decreases to 25% when treatment starts later (e.g., the second week after diagnosis) [10].

Anticoagulant therapy should continue for 3–6 months to complete recanalization [10].

#### **3.4 Anticoagulants for chronic PVT**

Anticoagulants are only administered in 30% of chronic PVT chases, which reflects concerns about their use in the presence of varices and coagulation dysfunction. However, the number of hemorrhage episodes in chronic PVT patients on anticoagulants has not shown to increase; however, long-term follow-up may be needed. Anticoagulants have proven effective in the prevention of new thrombotic events with a low mortality rate [10].

Anticoagulants include vitamin K antagonists (warfarin), low-molecular-weight heparin (enoxaparin), and unfractionated heparin (standard heparin). Direct oral anticoagulants include direct oral anti-activated factor X (Xa) (e.g., rivaroxaban) and direct oral antithrombin (IIa) (e.g., dabigatran). These medications are used to manage thrombosis in beta-thalassemia patients [2].

In hemoglobinopathies including thalassemia, rivaroxaban is effective without increasing the risk of bleeding or thrombosis after 18 years of age [2].
