SIDE EFFECTS: Diarrhea, nausea, mouth sores, dry/itchy skin, tiredness, back pain, headache, or loss of appetite may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly. Remember that your doctor has prescribed this medication because he or she 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, such as: easy bruising/bleeding, changes in your nails (such as nail tenderness/irritation/redness, change in nail color), signs of eye disease (such as vision changes, eye redness/pain, light sensitivity, eye discharge), signs of low level of sodium in the blood (such as nausea, extreme drowsiness, mental/mood changes, seizures). Get medical help right away if you have any very serious side effects, such as: slow/fast/irregular heartbeat, severe dizziness, fainting, slow/shallow breathing, symptoms of heart failure (such as shortness of breath, swelling ankles/feet, unusual tiredness, unusual/sudden weight gain), new or worsening symptoms of lung disease (such as trouble breathing, chest pain, cough, fever), signs of blood clots (such as pain/swelling/warmth in the groin/calf). 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 infections (such as sore throat that doesn't go away, fever, chills). 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, such as: 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.

PRECAUTIONS: Before taking osimertinib, 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. Osimertinib may cause a condition that affects the heart rhythm (QT prolongation). QT prolongation can rarely cause serious (rarely fatal) fast/irregular heartbeat and other symptoms (such as severe dizziness, fainting) that need medical attention right away. The risk of QT prolongation may be increased if you have certain medical conditions or are taking other drugs that may cause QT prolongation. Before using osimertinib, tell your doctor or pharmacist of all the drugs you take and if you have any of the following conditions: certain heart problems (heart failure, slow heartbeat, QT prolongation in the EKG), family history of certain heart problems (QT prolongation in the EKG, sudden cardiac death). Low levels of potassium or magnesium in the blood may also increase your risk of QT prolongation. This risk may increase if you use certain drugs (such as diuretics/"water pills") or if you have conditions such as severe sweating, diarrhea, or vomiting. Talk to your doctor about using osimertinib safely. This drug may cause blurred vision. Do not drive, use machinery, or do any activity that requires clear vision until you are sure you can perform such activities safely. Limit alcoholic beverages. Osimertinib can make you more likely to get infections or may worsen any current infections. Avoid contact with people who have infections that may spread to others (such as chickenpox, measles, flu). Consult your doctor if you have been exposed to an infection or for more details. Do not have immunizations/vaccinations without the consent of your doctor. Avoid contact with people who have recently received live vaccines (such as flu vaccine inhaled through the nose). To lower the chance of getting cut, bruised, or injured, use caution with sharp objects like razors and nail cutters, and avoid activities such as contact sports. 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 QT prolongation (see above). This medication is not recommended for use during pregnancy. It may harm an unborn baby. It is important to prevent pregnancy while taking this medication and after treatment. Females should use reliable forms of birth control (such as condoms, birth control pills) during treatment and for 6 weeks after the end of treatment. Males with female partners should use reliable forms of birth control (such as condoms) during treatment and for 4 months after the end of treatment. If you become pregnant or think you may be pregnant or may have caused pregnancy, tell your doctor right away. It is unknown if this drug passes into breast milk. Because of the possible risk to the infant, breast-feeding is not recommended while using this drug and for 2 weeks after the end of treatment. Consult your doctor before breast-feeding.

DRUG INTERACTIONS: 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.

OVERDOSE: 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 their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center.