Avapritinib is used to treat a certain type of gastrointestinal stromal tumor (GIST; a type of tumor that grows in the wall of the stomach, intestine [bowel], or esophagus [tube that connects the throat with the stomach]) in adults that has spread to other parts of the body or that cannot be removed by surgery. It is also used to treat certain types of mastocytosis (a blood disorder in which there are too many mast cells [a certain kind of white blood cell]). Avapritinib is in a class of medications called kinase inhibitors. It works by blocking the action of the abnormal protein that signals cancer cells to multiply. This helps to stop or slow the spread of cancer cells.

Avapritinib comes as a tablet to take by mouth. It is usually taken once daily on an empty stomach, at least 1 hour before and 2 hours after a meal. Take avapritinib at around the same time every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take avapritinib exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

If you vomit after taking avapritinib, do not take another dose. Continue your regular dosing schedule.

Your doctor may decrease your avapritinib dose or temporarily or permanently stop your treatment depending on how well the medication works for you and if you experience any side effects. Be sure to tell your doctor how you are feeling during your treatment with avapritinib. Do not stop taking avapritinib without talking to your doctor.

Ask your pharmacist or doctor for a copy of the manufacturer’s information for the patient.

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

Before taking avapritinib,

• tell your doctor and pharmacist if you are allergic to avapritinib, any other medications, or any of the ingredients in avapritinib tablets. Ask your pharmacist for a list of the ingredients.
• tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, and nutritional supplements you are taking or plan to take. Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
• The following nonprescription or herbal products may interact with avapritinib: St. John’s wort. Be sure to let your healthcare provider know that you are taking this medication before you start taking avapritinib. Do not start this medication while taking avapritinib without talking to your healthcare provider.
• tell your doctor if you have or have ever had bleeding in your brain, a low platelet (a type of blood cell) counts, or liver or kidney disease. Also, tell your doctor if you have or have ever had a stroke, especially if it has happened within the past year.
• tell your doctor if you are pregnant, plan to become pregnant, or if you plan on fathering a child. If you are female, you will need to take a pregnancy test before you start treatment and use birth control to prevent pregnancy during your treatment and for 6 weeks after your final dose. If you are a male, you and your partner should use birth control during your treatment and for 6 weeks after your final dose. Talk to your doctor about birth control methods that you can use during your treatment. If you or your partner become pregnant while taking avapritinib, call your doctor immediately. Avapritinib may harm the fetus.
• tell your doctor if you are breast-feeding. You should not breast-feed while you are taking avapritinib and for at least 2 weeks after your final dose.
• you should know that this medication may decrease fertility in men and women. Talk to your doctor about the risks of taking avapritinib.
• you should know that avapritinib may make you dizzy, drowsy, or confused. Do not drive a car or operate machinery until you know how this medication affects you.
• plan to avoid unnecessary or prolonged exposure to sunlight and to wear protective clothing, sunglasses, and sunscreen during your treatment with avapritinib and for 1 week after your final dose. Avapritinib may make your skin sensitive to sunlight.

Talk to your doctor about eating grapefruit and drinking grapefruit juice while taking this medication.

Take the missed dose as soon as you remember it. However, if the next dose is due in less than 8 hours, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

Avapritinib may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• stomach pain
• vomiting
• nausea
• diarrhea
• constipation
• heartburn
• headache
• tiredness or weakness
• difficulty falling asleep or staying asleep
• hair loss
• hair color changes
• weight loss
• teary eyes
• taste changes
• rash

Some side effects can be serious. If you experience any of these symptoms, stop taking avapritinib and call your doctor immediately or get emergency medical treatment:

• swelling of face, eyes, mouth, or throat
• swelling of hands, ankles, or feet
• vomiting blood or material that looks like coffee grounds or red or tarry black stools
• severe headache, vomiting, confusion, vision problems, drowsiness, extreme tiredness, or weakness on one side of your body
• forgetfulness, confusion, drowsiness or difficulty staying awake, dizziness, trouble thinking, difficulty speaking, hallucinations, or changes in mood or behavior
• shortness of breath
• fever or other signs of infection

Avapritinib may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration’s (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from light excess heat and moisture (not in the bathroom).

It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach. http://www.upandaway.org

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA’s Safe Disposal of Medicines website (http://goo.gl/c4Rm4p) for more information if you do not have access to a take-back program.

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at https://www.poisonhelp.org/help. If the victim has collapsed, had a seizure, has trouble breathing, or can’t be awakened, immediately call emergency services at 911.

Keep all appointments with your doctor and the laboratory. Your doctor will order a lab test before you begin your treatment to see whether your cancer can be treated with avapritinib. Your doctor may order certain lab tests to check your body’s response to avapritinib.

Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.

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