Fostamatinib Disodium: uses, dosing, side effects & brands
Fostamatinib Disodium is a medicine sold in the U.S. under one brand, for thrombocytopenia. Below: what the FDA label says, every product that contains it, what the pills look like, and its recall record.
Key facts
- Treats
- Thrombocytopenia
- Available as
- Tablet
- Sold as
- Tavalisse
- Prescription?
- Prescription only
- Generic available?
- Not in our catalog
How fostamatinib disodium is dosed
From the FDA label for Tavalisse (application NDA209299). Other fostamatinib disodium products — different forms, different strengths — are dosed differently. Follow the label for the one you were prescribed.
Initiate TAVALISSE at 100 mg orally twice daily with or without food. After 4 weeks, increase to 150 mg twice daily, if needed, to achieve platelet counts of at least 50 × 10 9 /L as necessary to reduce the risk of bleeding. ( 2.1 ) Manage adverse reactions using dose reduction, interruption of treatment, or discontinuation. ( 2.3 ) Discontinue TAVALISSE after 12 weeks of treatment if the platelet count does not increase to a level sufficient to avoid clinically important bleeding. ( 2.5 ) 2.1 Recommended Dosage Initiate TAVALISSE at a dose of 100 mg taken orally twice daily. After a month, if platelet count has not increased to at least 50 × 10 9 /L, increase TAVALISSE dose to 150 mg twice daily. Use the lowest dose of TAVALISSE to achieve and maintain a platelet count at least 50 × 10 9 /L as necessary to reduce the risk of bleeding. TAVALISSE may be taken with or without food. In the case of a missed dose of TAVALISSE, instruct patients to take their next dose at its regularly scheduled time. 2.2 Monitoring After obtaining baseline assessments: Monitor CBCs, including platelet counts, monthly until a stable platelet count (at least 50 × 10 9 /L) is achieved. Thereafter, continue to monitor CBCs, including neutrophils, regularly. Monitor liver function tests (LFTs) (e.g., ALT, AST, and bilirubin) monthly. Monitor blood pressure every 2 weeks until establishment of a stable…
Fostamatinib Disodium side effects
The following clinically important adverse reactions, that can become serious are described elsewhere in the labeling: Hypertension [ see Warnings and Precautions (5.1) ] Hepatotoxicity [ see Warnings and Precautions (5.2) ] Diarrhea [ see Warnings and Precautions (5.3) ] Neutropenia [ see Warnings and Precautions (5.4) ] The most common adverse reactions (≥5% and more than placebo) are diarrhea, hypertension, nausea, respiratory infection, dizziness, ALT/AST increased, rash, abdominal pain, fatigue, chest pain and neutropenia. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Rigel Pharmaceuticals, Inc. at 1-800-983-1329 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. TAVALISSE was studied in two randomized, double-blind, placebo-controlled trials that were identical in design. The data described below reflect exposure to TAVALISSE in 102 patients with chronic ITP who had received one or more prior ITP treatment(s). Groups were stratified with respect to splenectomy and severity of thrombocytopenia. Patients randomized to the TAVALISSE arm received 100 mg orally twice daily.…
Who shouldn’t take fostamatinib disodium
None. None. ( 4 )
Fostamatinib Disodium drug interactions
Strong CYP3A4 Inhibitors: Concomitant use with a strong CYP3A4 inhibitor increases exposure to R406 (the major active metabolite).( 7 ) Strong CYP3A4 Inducers: Concomitant use is not recommended. ( 7 ) 7.1 Effect of Other Drugs on TAVALISSE Strong CYP3A4 Inhibitors Concomitant use with strong CYP3A4 inhibitors increases exposure to R406 (the major active metabolite), which may increase the risk of adverse reactions. Monitor for toxicities of TAVALISSE that may require dose reduction (see Table 1 ) when given concurrently with a strong CYP3A4 inhibitor [see Dosage and Administration (2.4) and Clinical Pharmacology (12.3) ] . Strong CYP3A4 Inducers Concomitant use with a strong CYP3A4 inducer reduces exposure to R406. Concomitant use of TAVALISSE with strong CYP3A4 inducers is not recommended [see Clinical Pharmacology (12.3) ] . 7.2 Effect of TAVALISSE on Other Drugs CYP3A4 Substrates Concomitant use of TAVALISSE may increase concentrations of some CYP3A4 substrate drugs. Monitor for toxicities of CYP3A4 substrate drug that may require dosage reduction when given concurrently with TAVALISSE [see Clinical Pharmacology (12.3) ] . BCRP Substrates Concomitant use of TAVALISSE may increase concentrations of BCRP substrate drugs (e.g., rosuvastatin). Monitor for toxicities of BCRP substrate drug that may require dosage reduction when given concurrently with TAVALISSE [see Clinical Pharmacology (12.3) ] . P-Glycoprotein (P-gp) Substrates Concomitant use of TAVALISSE may increase concentrations of P-gp substrates (e.g., digoxin). Monitor for toxicities of the P-gp substrate drug that may require dosage reduction when given concurrently with TAVALISSE [see Clinical Pharmacology (12.3) ] .
Every fostamatinib disodium product we track (1)
Same active ingredient — different manufacturer, form, price and FDA recall record. That last one is what our independent score measures.
Only one: Tavalisse.
What people report to the FDA about fostamatinib disodium
The FDA Adverse Event Reporting System (FAERS) collects reports from patients and clinicians. It holds 338 reports naming fostamatinib disodium, and the FDA flagged 96% of those reports as serious. The effects reported most often — leaving out reports about overdose, misuse or the condition being treated, which dominate the raw list for common medicines:
- hypertension44 reports
- diarrhoea37 reports
- hepatic function abnormal25 reports
- sepsis21 reports
- platelet count decreased20 reports
- pneumonia18 reports
- anaemia16 reports
- hospitalisation13 reports
Read these as a signal, not a rate. A report does not mean fostamatinib disodium caused the effect — anyone can file one, and many describe people taking several medicines for several conditions. Crucially there is no denominator: FAERS does not record how many people took the drug, so these counts cannot be turned into “X% of patients” — a bigger number often just means a more widely used or more talked-about drug. Duplicates exist, and publicity drives reporting. For what is actually established, read the FDA label section above.
Source: openFDA drug/event (FAERS), retrieved July 25, 2026.
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Frequently asked questions
What is fostamatinib disodium?
Fostamatinib is a tyrosine kinase inhibitor. TAVALISSE is formulated with the disodium hexahydrate salt of fostamatinib, a phosphate prodrug that converts to its pharmacologically active metabolite, R406, in vivo .
Can you take fostamatinib disodium with other medicines?
It depends on the medicine. We check it against the FDA labels rather than guessing: our interaction checker searches each drug's own label for the other and quotes what it says, naming the section it came from. Run fostamatinib disodium against whatever else you take — and remember that a label not naming a drug is not the same as that combination being safe.
What forms does fostamatinib disodium come in?
Across the brands we track, fostamatinib disodium is currently marketed as tablet, per the FDA's National Drug Code Directory. Each form is dosed differently — follow the label for the exact product you were prescribed.
Is there a generic fostamatinib disodium?
We do not currently list a generic-labelled fostamatinib disodium product. That does not always mean none exists — it means none appears under a generic name in the FDA data we track. Ask your pharmacist.
Cite this page
- APA
- pharmaranks. (2026, July 24). Fostamatinib Disodium: uses, dosing, side effects & brands. https://pharmaranks.com/drugs/fostamatinib-disodium
- MLA
- “Fostamatinib Disodium: uses, dosing, side effects & brands.” pharmaranks, 24 July 2026, https://pharmaranks.com/drugs/fostamatinib-disodium.
We summarise public FDA and NIH sources — for a clinical claim, cite the primary source we link to as well.
Sources: FDA openFDA drug label, National Drug Code Directory, and Enforcement (recall) database. This page reproduces public FDA data and is not medical advice. Dosing is set by your prescriber.
Read the full FDA label for fostamatinib disodium on DailyMed (NIH) ↗.