Gilteritinib may cause a serious or life-threatening group of symptoms called differentiation syndrome. Your doctor will monitor you carefully to see whether you are developing this syndrome. If you experience any of the following symptoms, call your doctor immediately: fever, cough, rash, sudden weight gain, dizziness, decreased urination, swelling of your arms or legs, shortness of breath, difficulty breathing, chest pain, or bone pain. These symptoms may occur up to 3 months after starting treatment with gilteritinib. At the first sign that you are developing differentiation syndrome, your doctor will prescribe medications to treat the syndrome, and may tell you to stop taking gilteritinib for some time.

Your doctor or pharmacist will give you the manufacturer’s patient information sheet (Medication Guide) when you begin treatment with gilteritinib and each time you refill your prescription. Read the information carefully and ask your doctor or pharmacist if you have any questions. You can also visit the Food and Drug Administration (FDA) website (http://www.fda.gov/Drugs/DrugSafety/ucm085729.htm) or the manufacturer’s website to obtain the Medication Guide.

Gilteritinib is used to treat a certain type of acute myeloid leukemia (AML) that has worsened or returned after treatment with other chemotherapy medications. Gilteritinib is in a class of medications called kinase inhibitors. It works by blocking the action of a certain naturally occurring substance that may be needed to help cancer cells multiply.

Gilteritinib comes as a tablet to take by mouth. It is usually taken once daily with or without food for at least 6 months. Take gilteritinib 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 gilteritinib exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

Swallow the tablets whole with water; do not split, chew, or crush them.

Your doctor may adjust your dose or temporarily or permanently stop your treatment depending on how well the medication works for you and if you experience any side effects. Talk to your doctor about how you are feeling during your treatment. Continue to take gilteritinib even if you feel well. Do not stop taking gilteritinib without talking to your doctor.

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

Before taking gilteritinib,

• tell your doctor and pharmacist if you are allergic to gilteritinib, any other medications, or any of the ingredients in gilteritinib tablets. Ask your pharmacist for a list of the ingredients.
• tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention any of the following: certain antifungals such as fluconazole (Diflucan), itraconazole (Onmel, Sporanox), and ketoconazole; clarithromycin (Biaxin, in PrevPac); escitalopram (Lexapro); fluoxetine (Prozac); certain medications for human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS) such as efavirenz (Sustiva, in Atripla), indinavir (Crixivan), nelfinavir (Viracept), nevirapine (Viramune), ritonavir (Norvir, in Kaletra), and saquinavir (Invirase); certain medications for seizures such as carbamazepine (Carbatrol, Epitol, Tegretol, others), phenobarbital, and phenytoin (Dilantin, Phenytek); nefazodone; pioglitazone (Actos); rifabutin (Mycobutin); rifampin (Rifadin, Rimactane, in Rifamate, in Rifater); and sertraline (Zoloft). Your doctor may need to change the doses of your medications or monitor you carefully for side effects. Many other medications may also interact with gilteritinib, so be sure to tell your doctor about all the medications you are taking, even those that do not appear on this list.
• tell your doctor what herbal products you are taking, especially St. John’s wort.
• tell your doctor if you have or have ever had a QT interval prolongation (an irregular heart rhythm that can lead to fainting, loss of consciousness, seizures, or sudden death); a slow, fast, or irregular heartbeat; or low levels of potassium or magnesium in your blood.
• tell your doctor if you are pregnant, plan to become pregnant, or if you plan to father a child. You or your partner should not become pregnant while you are taking gilteritinib. If you are female, you will need to have a pregnancy test at least 7 days before you start treatment, and you should use birth control during your treatment and for 6 months after your final dose. If you are male, you and your partner should use birth control to prevent pregnancy during your treatment and for 4 months 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 gilteritinib, call your doctor. Gilteritinib may harm the fetus.
• tell your doctor if you are breastfeeding. You should not breastfeed during your treatment with gilteritinib and for 2 months after your final dose.

Unless your doctor tells you otherwise, continue your normal diet.

Take the missed dose as soon as you remember it. However, if it is less than 12 hours before your next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

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

• joint or muscle pain
• extreme tiredness
• nausea
• vomiting
• diarrhea
• mouth sores
• change in the ability to taste food
• headache
• loss of appetite
• difficulty falling asleep or staying asleep

Some side effects can be serious. If you experience any of these symptoms or those in the IMPORTANT WARNING section, call your doctor immediately or get emergency medical treatment:

• seizures; headache; decreased alertness; confusion; or vision changes
• fast, pounding, or irregular heartbeat; fainting; loss of consciousness; or seizures
• ongoing pain that begins in the stomach area but may spread to the back that may occur with or without nausea and vomiting

Gilteritinib 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 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 gilteritinib. Your doctor will also order certain lab tests before and during your treatment to check your body’s response to gilteritinib. Your doctor may also order an electrocardiogram (ECG; test that measures the electrical activity in the heart) before and during your treatment.

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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