This medication is used to treat people with a certain blood disorder known as chronic immune thrombocytopenia-ITP. This is a condition where the amount of one type of cell in your blood (platelets) is lower than normal. ITP can lead to serious bleeding problems. Fostamatinib belongs to a class of drugs known as spleen tyrosine kinase inhibitors. It works by increasing platelets in your blood.

Read the Patient Information Leaflet if available from your pharmacist before you start taking fostamatinib and each time you get a refill. If you have any questions, ask your doctor or pharmacist.

Take this medication by mouth with or without food as directed by your doctor, usually twice daily. The dosage is based on your medical condition and response to treatment.

Use this medication regularly to get the most benefit from it. To help you remember, take it at the same times each day.

Diarrhea is a common side effect. Tell your doctor promptly if you have diarrhea. Ask your healthcare provider about how to manage diarrhea, such as by changing your diet, taking anti-diarrhea medicine, and drinking enough water to prevent dehydration.

Nausea, upset stomach, abdominal pain, dizziness, or tiredness may also occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

This medication may cause or worsen high blood pressure. Your blood pressure should be checked regularly. Your doctor may start or adjust medication(s) to treat high blood pressure.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including:

• bruising/bleeding

Fostamatinib may rarely cause serious (possibly fatal) liver disease. Get medical help right away if you have any symptoms of liver damage, such as:

• nausea/vomiting that doesn't stop
• loss of appetite
• stomach/abdominal pain
• yellowing eyes/skin
• dark urine

This medication may lower your ability to fight infections. This may make you more likely to get a serious (rarely fatal) infection or make any infection you have worse. Tell your doctor right away if you have any signs of infection (such as sore throat that doesn't go away, fever, chills, cough).

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• rash
• itching/swelling (especially of the face/tongue/throat)
• severe dizziness
• trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before taking fostamatinib, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• high blood pressure
• liver problems
• surgery to remove spleen
• bleeding/blood problems (such as blood clots)

This drug may make you dizzy. Alcohol or marijuana (cannabis) can make you more dizzy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

Fostamatinib can make you more likely to get infections or may make current infections worse. Stay away from anyone who has an infection that may easily spread (such as chickenpox, COVID-19, measles, flu). Talk to your doctor if you have been exposed to an infection or for more details.

Tell your health care professional that you are using fostamatinib before having any immunizations/vaccinations. Avoid contact with people who have recently received live vaccines (such as flu vaccine inhaled through the nose).

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

Older adults may be more sensitive to the side effects of this drug, especially high blood pressure.

Tell your doctor if you are pregnant or plan to become pregnant. You should not become pregnant while using fostamatinib. Fostamatinib may harm an unborn baby. Ask about reliable forms of birth control while using this medication and for at least 1 month after the last dose. If you become pregnant, talk to your doctor right away about the risks and benefits of this medication.

It is unknown if this medication passes into breast milk. Because of the possible risk to the infant, breastfeeding is not recommended while using this medication and for at least 1 month after the last dose. Consult your doctor before breastfeeding.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Other medications can affect the removal of fostamatinib from your body, which may affect how fostamatinib works. Examples include azole antifungals (such as ketoconazole/itraconazole), rifamycins (such as rifampin/rifampicin), St. John's wort, drugs used to treat seizures (such as carbamazepine, phenytoin), among others.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669.

Do not share this medication with others.

Lab and/or medical tests (such as complete blood count, liver function, blood pressure) should be done while you are taking this medication. Keep all medical and lab appointments.

If you miss a dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.

Store in the original bottle at room temperature away from light and moisture. Do not store in the bathroom. Keep the drying agent (desiccant) in the bottle. Some brands of this medication should be used within 60 days of opening the bottle. Check the product package or ask your pharmacist about your specific brand. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.

Your condition can cause complications in a medical emergency. For information about enrolling in MedicAlert, call 1-888-633-4298 (US) or 1-800-668-1507 (Canada).