Tavalisse (Fostamatinib) - Oral

What Is Tavalisse?

Tavalisse (fostamatinib) is a tablet in the class of prescription medications called tyrosine kinase inhibitors used to treat a condition called immune thrombocytopenia (ITP, also called idiopathic thrombocytopenic purpura) in adults. It can be used when other treatments for ITP have not worked.

In ITP, the immune system is abnormally breaking down platelets (thrombocytes) in the body. Platelets are the cells in the blood that help heal damaged blood vessel walls and clot together to stop bleeding. Tavalisse blocks the process by which the immune system destroys platelets.

This medication is available as a tablet to be taken by mouth.

Drug Facts

Generic Name: Fostamatinib

Brand Name(s): Tavalisse

Drug Availability: Prescription

Administration Route: Oral

Therapeutic Classification: Kinase inhibitor

Available Generically: No

Controlled Substance: N/A

Active Ingredient: Fostamatinib disodium

Dosage Form(s): Tablet

What Is Tavalisse Used For?

Tavalisse treats ITP in adults who have insufficient responses to other therapies.

ITP is a type of platelet disorder caused by low levels of blood platelets. In ITP, your blood does not clot as well as it should, which can lead to bleeding that is hard to stop. This condition can be short-term (acute) or long-term (chronic); generally, chronic ITP lasts six months or longer. Tavalisse will help increase your blood platelet levels to reduce and prevent bleeding.

While ITP may not cause symptoms, there are signs to watch for. Excessive bleeding is one.

Signs of excessive bleeding can include:

  • Petechiae (small, flat red spots on the skin caused by leaking blood vessels)
  • Purpura (bleeding in the skin that causes red, purple, or brownish-yellow spots)
  • Bruises that form easily or hematomas (pooling of blood from ruptured blood vessels)
  • Long-lasting or hard-to-stop nosebleeds or gum bleeding
  • Blood in the urine or stool
  • Abnormally heavy menstrual bleeding
  • Extreme tiredness

How to Take Tavalisse

Tavalisse is taken by mouth twice a day, with or without food.

The goal of treatment is to increase and maintain your platelet count. Your healthcare provider will monitor your platelet count throughout treatment to determine if any dosage adjustments are needed.


Store Tavalisse at room temperature (between 68 F ad 77 F). Inside the packaging are little canisters called desiccants. These help to keep the medication dry and should not be removed.

How Long Does Tavalisse Take to Work?

Two phase 3 studies evaluated fostamatinib use in people with long-standing ITP for whom other treatments had already been tried. Treatment responses were observed within 12 weeks in 43% of those treated with fostamatinib and 14% of those who received a placebo. People who were earlier in their ITP seemed to have a higher response rate to fostamatinib.

What Are the Side Effects of Tavalisse?

This is not a complete list of side effects and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your healthcare provider. You may report side effects to the FDA at fda.gov/medwatch or 1-800-FDA-1088.

Common Side Effects

Some side effects may be experienced when taking Tavalisse. The most common side effects include:

  • Diarrhea
  • High blood pressure (hypertension)
  • Nausea
  • Respiratory infection
  • Dizziness
  • Elevated liver enzymes
  • Rash
  • Tiredness
  • Abdominal pain
  • Chest pain
  • Low neutrophil count (neutropenia)

Most of these side effects are mild and will resolve on their own. However, in some cases, medication management might help. For example, your healthcare provider may prescribe antihypertensive treatment if you have high blood pressure. Talk to your healthcare provider if your side effects persist or worsen.

Severe Side Effects

Call your healthcare provider immediately if you are experiencing serious side effects. Call 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency. Serious side effects can include the following:

  • High blood pressure: Treatment with blood pressure-lowering medications may be necessary.
  • Hypertensive crisis, which is defined as systolic blood pressure (BP) measurement over 180 and diastolic BP over 120 millimeters of mercury (mmHg): More aggressive antihypertensive therapy may be necessary. However, if BP remains too high, your healthcare provider may stop your treatment with Tavalisse.
  • Neutropenia (very low white blood cells): You may need to temporarily stop treatment if required if neutrophil levels remain low. Once restarted, you may take a lower dose.
  • Liver toxicity: Your healthcare provider may monitor liver function tests monthly during treatment. If your ALT and AST levels are too high, your treatment may be reduced or stopped.

Report Side Effects

Tavalisse may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your healthcare provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

Dosage: How Much Tavalisse Should I Take?

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The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For oral dosage form (tablets):
    • For thrombocytopenia:
      • Adults—The starting dose is usually 100 milligrams (mg) 2 times a day. Your doctor may increase your dose as needed.
      • Children—Use is not recommended.


If significant side effects are experienced while taking Tavalisse, your healthcare provider may reduce the dose of Tavalisse based on the side effects experienced. The amount of Tavalisse may also be adjusted depending upon how the platelet count responds to the medication.

Missed Dose

If you miss a dose of Tavalisse, skip the missed dose and resume taking it at the next scheduled time.

Overdose: What Happens If I Take Too Much Tavalisse?

If too much Tavalisse has been taken, notify the healthcare team immediately. Observation for severe side effects may be needed, and if necessary, supportive measures may need to be taken.

What Happens If I Overdose on Tavalisse?

If you think you or someone else may have overdosed on Tavalisse, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn't breathing after taking Tavalisse, call 911 immediately.


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It is very important that your doctor check your progress at regular visits to make sure this medicine is working properly. Blood tests may be needed to check for unwanted effects.

Using this medicine while you are pregnant can harm your unborn baby. Use an effective form of birth control to keep from getting pregnant during treatment with this medicine and for at least 1 month after the last dose. If you think you have become pregnant while using this medicine, tell your doctor right away.

Your blood pressure might get too high while you are using this medicine. This may cause headaches, dizziness, or blurred vision. You might need to measure your blood pressure at home. If you think your blood pressure is too high, call your doctor right away.

Check with your doctor right away if you have pain or tenderness in the upper stomach, pale stools, dark urine, loss of appetite, nausea, vomiting, or yellow eyes or skin. These could be symptoms of a serious liver problem.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

What Are Reasons I Shouldn’t Take Tavalisse?

Tavalisse should not be taken by people who are pregnant, plan to become pregnant, or who are breastfeeding. Breastfeeding should be avoided while taking Tavalisse and for at least one month after stopping.

Tavalisse should also not be taken by children.

What Other Medications Interact With Tavalisse?

Tell your prescribing healthcare provider of all medications you are taking, as some interactions require dose adjustments or complete avoidance.

Tavalisse interacts with drugs that are strong cytochrome P450 (CYP) 3A4 inhibitors or inducers. CYP3A4 is a type of enzyme responsible for the metabolism of many medications. The induction or inhibition of this enzyme can result in drug-drug interactions.

Taking Tavalisse with a potent CYP3A4 inhibitor can increase exposure to the active metabolite, called R406, primarily metabolized by the CYP3A4 enzyme. Toxicities can occur, which may result in dose modifications. Examples of CYP3A4 inhibitors include but are not limited to:

Conversely, using Tavalisse with CYP3A4 inducers may decrease exposure to R406. It is not recommended to use these drugs together. Examples of CYP3A4 inducers include but are not limited to:

Ask your healthcare provider or a pharmacist if you are unsure whether you are taking a medication that may interfere with Tavalisse. Aside from medications, substances like St. John's wort and grapefruit juice can also interact with this medication. Therefore, it is important to share your use of all prescription and over-the-counter (OTC) drugs, vitamins, and herbal supplements with a healthcare provider.

What Medications Are Similar?

Tavalisse is the only medication in its class that treats chronic ITP by stopping the immune system from destroying blood platelets.

Other medications used to treat thrombocytopenia include:

  • Mulpleta (lusutrombopag): Lusutrombopag is a thrombopoietin receptor agonist that treats thrombocytopenia in adults with chronic liver disease scheduled to undergo a procedure.
  • Doptelet (avatrombopag): Avatrombopag is a thrombopoietin receptor agonist used to treat thrombocytopenia in adults with chronic liver disease scheduled to undergo a procedure and as second-line therapy for chronic ITP.

The above-listed medications are also used for certain types of thrombocytopenia under different circumstances. They do not belong to the same drug class as Tavalisse and do not work in the same way.

Frequently Asked Questions

  • What is Tavalisse used for?

    Tavalisse is used to treat ITP that has not been effectively treated by other measures. In ITP, the immune system is abnormally breaking down platelets in the body. Tavalisse helps increase platelet counts to reduce and prevent bleeding.

  • What are the side effects of Tavalisse?

    Side effects of Tavalisse can include:

    • High blood pressure
    • Diarrhea
    • Nausea
    • Respiratory infection
    • Dizziness
    • Elevated liver enzymes
    • Rash
    • Fatigue
    • Abdominal pain

    Most of the time, these side effects are mild and resolve on their own. In certain cases, you may need medication to manage your side effects, such as with high blood pressure.

  • How does Tavalisse work?

    Tavalisse works by targeting a specific enzyme in the body, which is called spleen tyrosine kinase. This enzyme is partly responsible for alerting the immune system to destroy platelets. Tavalisse blocks the enzyme from working, thereby inhibiting the destruction of platelets.

  • What medications should not be taken with Tavalisse?

    Certain medications may need to be stopped or doses adjusted when taking Tavalisse. Speak with your healthcare team about all medications or substance use, including prescription and OTC drugs, vitamins, or herbal supplements. Tavalisse should not be taken with CYP3A4 inducers, including medications like rifampin, phenytoin, and primidone. You may need a dosage adjustment in some cases, such as with strong CYP3A4 inhibitors.

How Can I Stay Healthy While Taking Tavalisse?

Discuss any questions or concerns while taking Tavalisse with your healthcare team. Side effects can occur, but that doesn't everyone develops them. Even if they do occur, they are likely to be mild and resolve on their own.

However, you should be aware of any new or worrisome side effects. Also, watch for abnormal bleeding or bruising that may signify problems with blood clotting.

In some cases, dosage adjustments may be needed based on your platelet counts, side effects, or response to treatment. Communicate how you are feeling with your healthcare provider at each follow-up visit. They will regularly check your platelet counts. You can even speak to a pharmacist if you notice any new side effects or have questions about drug interactions.

Medical Disclaimer

Verywell Health's drug information is meant for educational purposes only and is not intended to replace medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Food and Drug Administration. Tavalisse label.

  2. National Heart, Lung, and Blood Institute. Immune thrombocytopenia (ITP).

  3. McKeage K, Lyseng-Williamson KA. Fostamatinib in chronic immune thrombocytopenia: a profile of its use in the USA. Drugs Ther Perspect. 2018;34(10):451-456. doi:10.1007/s40267-018-0551-x

  4. Bussel J, Arnold DM, Grossbard E, Mayer J, Trelinski J, Homenda W, et al. Fostamatinib for the treatment of adult persistent and chronic immune thrombocytopenia: results of two phase 3, randomized, placebo-controlled trialsAm J Hematol. 2018;93:921–930. doi:10.1002/ajh.25125

  5. UpToDate. Cytochrome P450 3A (including 3A4) inhibitor and inducers.

  6. PubChem. Fostamatinib.

  7. Clemons Bankston P, Al-Horani RA. New small molecule drugs for thrombocytopenia: chemical, pharmacological, and therapeutic use considerations. Int J Mol Sci. 2019;20(12):3013. doi:10.3390/ijms20123013

By Julie Scott, MSN, ANP-BC, AOCNP
Julie is an Adult Nurse Practitioner with oncology certification and a healthcare freelance writer with an interest in educating patients and the healthcare community.