SIDE EFFECTS: Hair loss, dry skin, headache, nausea, vomiting, diarrhea, swelling of ankles/feet/hands, or joint/muscle pain may occur. If any of these effects persist or worsen, 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. Vemurafenib may cause other types of skin cancer (such as cutaneous squamous cell carcinoma and melanoma) that usually does not spread to other parts of the body. (See also Notes section.) Tell your doctor right away if you have any skin changes including: new wart, skin sore, change in size/color of a mole, skin bump that bleeds or does not heal. Infrequently, vemurafenib may also cause or worsen other types of cancer (such as non-cutaneous squamous cell carcinomas of the head and neck; cancers with RAS mutations, such as certain types of leukemias). Consult your doctor for more details. Get medical help right away if you have any very serious side effects, including: eye pain/swelling/redness, vision changes (such as blurred vision, blind spot/shadows in the center of your vision, sensitivity to light), fast/irregular heartbeat, severe dizziness, fainting, liver problems (symptoms such as loss of appetite, extreme tiredness, stomach/abdominal pain, dark urine, yellowing eyes/skin), pain/trouble swallowing, heartburn, signs of kidney problems (such as change in the amount of urine, pink/bloody urine). Vemurafenib can commonly cause a rash that is usually not serious. However, you may not be able to tell it apart from a rash that could be a sign of a severe reaction. Therefore, tell your doctor right away if you develop any rash. 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: fever, swollen lymph nodes, 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 vemurafenib, 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: radiation therapy. Vemurafenib 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 vemurafenib, 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 vemurafenib safely. This medication may make you more sensitive to the sun. Limit your time in the sun. Avoid tanning booths and sunlamps. Use sunscreen and wear protective clothing when outdoors. Tell your doctor right away if you get sunburned or have skin blisters/redness. 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 skin changes, nausea, decreased appetite, swelling of ankles/feet/hands, and QT prolongation (see above). Tell your doctor if you are pregnant or plan to become pregnant. You should not become pregnant while using vemurafenib. Vemurafenib may harm an unborn baby. Ask about reliable forms of birth control while using this medication and for 2 weeks after stopping treatment. 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 possible risk to the infant, breast-feeding while using this medication and for 2 weeks after stopping treatment is not recommended. 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. A product that may interact with this drug is: ipilimumab. Many drugs besides vemurafenib may affect the heart rhythm (QT prolongation), including amiodarone, dofetilide, quinidine, procainamide, sotalol, and certain antipsychotic medications (such as pimozide, thioridazine, ziprasidone), among others. Other medications can affect the removal of vemurafenib from your body, which may affect how vemurafenib works. Examples include azole antifungals (such as ketoconazole, itraconazole), macrolide antibiotics (such as clarithromycin), HIV protease inhibitors (such as ritonavir, atazanavir), telithromycin, nefazodone, St. John's wort, among others. Vemurafenib can slow down the removal of other medications from your body, which may affect how they work. Examples of affected drugs include caffeine, warfarin, among others.

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.