SIDE EFFECTS: See also Warning section. Pain/redness/swelling at the injection site, nausea, vomiting, diarrhea, stomach/abdominal pain, tiredness, cough, headache, or dizziness may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly. People using this medication may have serious side effects. However, your doctor has prescribed this drug because he or she has judged that the benefit to you is greater than the risk of side effects. Careful monitoring by your doctor may decrease your risk. Both leukemia and this medication can lower the body's ability to fight an infection. Tell your doctor promptly if you develop any signs of an infection such as unexplained fever, chills, or persistent sore throat. Tell your doctor right away if you have any serious side effects, including: easy bleeding/bruising, nosebleed, increased thirst, signs of kidney problems (such as change in the amount of urine), blurred vision, bone/joint pain, decreased appetite, unusual weight loss, muscle pain/stiffness/spasm, numbness/tingling, swollen hands/legs/feet, symptoms of liver disease (such as nausea/vomiting that doesn't stop, severe stomach/abdominal pain, yellowing eyes/skin, dark urine). Get medical help right away if you have any very serious side effects, including: chest pain, severe dizziness/fainting, fast/irregular heartbeat, coughing up blood, mental/mood changes (e.g., confusion), muscle weakness, seizures, bloody/black/tarry stool, vomit that looks like coffee grounds. People who are treated with this medication may rarely get other cancers. Consult your doctor for more details. 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 any 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 using this medication, tell your doctor or pharmacist if you are allergic to arsenic; 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: kidney disease, diabetes. Arsenic trioxide 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 arsenic trioxide, 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 arsenic trioxide safely. This drug may make you dizzy. Alcohol or marijuana 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. Arsenic trioxide can make you more likely to get infections or may worsen any current infections. Therefore, wash your hands well to prevent the spread of infection. 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. Older adults may be more sensitive to the side effects of this drug, especially QT prolongation (see above). Tell your doctor if you are pregnant or plan to become pregnant. Female patients should have a pregnancy test before starting this medication. You should not become pregnant while using arsenic trioxide. Arsenic trioxide may harm an unborn baby. Female patients should ask about reliable forms of birth control while using this medication and for 6 months after stopping treatment. Male patients with female partners should ask about reliable forms of birth control while using this medication and for 3 months after stopping treatment. If you or your partner become pregnant, talk to your doctor right away about the risks and benefits of this medication. This medication 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 last dose. 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. Many drugs besides arsenic trioxide may affect the heart rhythm (QT prolongation), including amiodarone, dofetilide, pimozide, procainamide, quinidine, sotalol, macrolide antibiotics (such as erythromycin), ziprasidone, among others. Therefore, before using arsenic trioxide, report all medications you are currently using to your doctor or pharmacist. Some products that may interact with this drug are: aspirin and other NSAIDs (e.g., ibuprofen), drugs that lower blood minerals (e.g., amphotericin B), drugs that may harm the immune system (e.g., chemotherapy). Check all prescription and nonprescription medicine labels carefully since many contain pain relievers/fever reducers (NSAIDs such as ibuprofen, naproxen, or aspirin) that may increase your risk of bleeding. Low-dose aspirin should be continued if prescribed by your doctor for heart attack or stroke prevention (usually at dosages of 81-325 milligrams a day). Consult your doctor or pharmacist for more details.

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. Symptoms of overdose may include: seizures, muscle weakness, confusion.