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Tyrosine kinase inhibitor

Tavalisse (fostamatinib) is a medicine used to treat adults with chronic immune thrombocytopenia (ITP) whose previous treatments have not worked well enough. It works by blocking a specific enzyme called SYK to help prevent the body from destroying its own platelets.

How it worksFostamatinib is a type of drug called a tyrosine kinase inhibitor. It specifically targets an enzyme called spleen tyrosine kinase (SYK). Its active form, R406, helps stop the body from using antibodies to destroy platelets.

Brand names:TAVALISSE

Used for
Chronic immune thrombocytopenia (ITP) in adults who did not respond well to other treatments
Conditions
Chronic immune thrombocytopenia (ITP)
Class
Kinase InhibitorTyrosine kinase inhibitorHematologicImmune System

How to take

FormsOral tablet
RoutesOral

Start with 100 mg twice daily. After 4 weeks, the dose may be increased to 150 mg twice daily if platelet counts have not reached at least 50 x 10^9/L.

You can take Tavalisse with or without food. If you miss a dose, take it at your next scheduled time.

Missed dose: Take your next dose at your regularly scheduled time.

Key warnings

  • ·High blood pressure: You need to monitor your blood pressure regularly.
  • ·Liver health: Your doctor will check your liver function tests monthly.
  • ·Diarrhea: Severe diarrhea may require stopping or lowering the dose.
  • ·Low white blood cells: Your doctor will monitor your blood counts for infections.
  • ·Pregnancy risk: This drug can cause harm to an unborn baby.

Do not use if

  • ·None listed

Side effects

Common

DiarrheaHigh blood pressureNauseaRespiratory infectionsDizzinessIncreased liver enzymes (ALT/AST)RashAbdominal painFatigueChest painLow white blood cell count (neutropenia)

Serious

  • ·Hypertension (high blood pressure)
  • ·Hepatotoxicity (liver injury)
  • ·Severe diarrhea
  • ·Neutropenia (low white blood cell count)
  • ·Fetal harm

Seek help if

  • ·Hypertensive crisis (very high blood pressure)
  • ·Severe diarrhea
  • ·Signs of infection (due to low white blood cells)
  • ·Signs of liver injury (nausea, vomiting, abdominal pain)

Interactions

  • ·Strong CYP3A4 inhibitors: These can increase the levels of the drug's active metabolite in your body, increasing the risk of side effects.
  • ·Strong CYP3A4 inducers: Using these with Tavalisse is not recommended as they may lower the drug's effectiveness.
  • ·BCRP substrates (like rosuvastatin): Tavalisse may increase levels of these drugs.
  • ·P-gp substrates (like digoxin): Tavalisse may increase levels of these drugs.
FoodTaking Tavalisse with a high-calorie, high-fat meal can increase the amount of the active drug in your system.

Special populations

PregnancyFostamatinib can cause harm to a fetus. Women of reproductive age should use effective birth control during treatment and for at least 1 month after the last dose. If you are pregnant or plan to become pregnant, tell your doctor immediately.

BreastfeedingDo not breastfeed while taking Tavalisse. You should wait at least 1 month after your last dose before breastfeeding.

PediatricTavalisse is not recommended for people under 18 years old because it may affect growing bones.

GeriatricIn clinical studies, older adults (65+) experienced more serious side effects and high blood pressure compared to younger patients, though the drug was just as effective.

Talk to your doctor

Monitor

  • ·Blood pressure
  • ·Liver function tests (ALT, AST, bilirubin)
  • ·Complete blood counts (platelets, neutrophils)
  • ·Signs of infection

Questions to ask

  • ·How often will my blood pressure and liver function be monitored?
  • ·What should I do if I experience severe diarrhea?
  • ·How should I manage my other medications while taking Tavalisse?
  • ·What are the risks to my bone health if I take this long-term?

Pharmacokinetics

OnsetThe active metabolite R406 reaches peak levels in about 1.5 hours
Half-lifeApproximately 15 hours
BioavailabilityThe absolute bioavailability of the active metabolite R406 is 55%
Protein bindingR406 is 98.3% protein bound in human plasma
MetabolismTavalisse is converted in the gut to R406, which is metabolized by CYP3A4 and UGT1A9
ExcretionApproximately 80% of the R406 metabolite is excreted in feces and 20% in urine

Practical

OverdoseThere is no specific antidote for an overdose. If an overdose occurs, you should be monitored closely for side effects and treated with supportive care.

Ingredients

Inactive

mannitolsodium bicarbonatesodium starch glycolatepovidonemagnesium stearatepolyvinyl alcoholtitanium dioxidepolyethylene glycol 3350talciron oxide yellowiron oxide red

Educational summary derived from FDA labeling, AI-assisted. Not medical advice — consult a healthcare professional. Updated 2026-04-26.