Immune thrombocytopenia often persists and develops into a chronic disease, seriously affecting patients' life and health. Fostamatinib (Tavalisse) is the world's first Syk inhibitor, which can be used to treat chronic immune thrombocytopenia. Then, what are the specific usage and dosage of fostamatinib?

What is the usage and dosage of fostamatinib (Tavalisse)?

Recommended Dosage

(1) The recommended starting dose of fostamatinib is 100mg orally, twice daily. After one month, if the platelet count does not increase to ≥50×10⁹/L, the dose of fostamatinib is increased to 150mg twice daily.

(2) Use the lowest dose of fostamatinib to achieve and maintain a platelet count of ≥50×10⁹/L, so as to reduce the risk of bleeding.

(3) Fostamatinib can be taken with or without food. If a dose of fostamatinib is missed, instruct the patient to take the next dose as scheduled according to the medication plan.

Monitoring

(1) Monitor the complete blood count (CBC) including platelet count once a month until the platelet count (at least 50×10⁹/L) reaches a stable level, and then continue to regularly monitor the complete blood count including neutrophil count.

(2) Monitor liver function tests (LFTs) once a month, such as alanine transaminase (ALT), aspartate transaminase (AST) and bilirubin.

(3) Monitor blood pressure every 2 weeks until the dose is stable, and then once a month thereafter.

Dose Adjustment for Adverse Reactions

Recommendations for dose adjustment of fostamatinib are based on the patient's individual safety and tolerability. The management of some adverse reactions may require temporary suspension, dose reduction or discontinuation of the drug. Table 1 provides the recommended dose reduction scheme based on the total daily dose. For example, if the patient is taking the maximum dose when an adverse reaction occurs, the first dose reduction will be from 300mg/day to 200mg/day. 

Dose Adjustment for Drug Interactions

Concomitant use of fostamatinib with strong CYP3A4 inhibitors will increase the exposure of R406 (the main active metabolite). When used in combination with strong CYP3A4 inhibitors, it is necessary to monitor the dose-related toxicity of fostamatinib and consider whether dosage adjustment is needed.

Discontinuation

If the platelet count still does not increase to a level sufficient to avoid clinically severe bleeding, discontinue fostamatinib after 12 weeks of treatment.