SIDE EFFECTS: See also Warning section. Nausea or vomiting may occur. Giving this medication after meals may help lessen these effects. Temporary hair loss may also occur. If any of these effects last or get worse, 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. Tell your doctor right away if you have any serious side effects, including: diarrhea, new or worsening joint/muscle pain. Get medical help right away if you have any very serious side effects, including: symptoms of liver disease (such as nausea/vomiting that doesn't stop, stomach/abdominal pain, dark urine, yellowing eyes/skin). This medication may increase your risk of getting a rare but very serious (possibly fatal) brain infection (progressive multifocal leukoencephalopathy-PML). Get medical help right away if you have any of these side effects: clumsiness, loss of coordination/balance, weakness, sudden change in your thinking (such as confusion, difficulty concentrating, memory loss), difficulty talking/walking, seizure, vision changes. 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 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 azathioprine, tell your doctor or pharmacist if you are allergic to it; or to mercaptopurine; 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: kidney disease, liver disease, cancer, a certain enzyme disorder (TPMT deficiency). This medication may increase your risk of developing skin cancer. Limit your time in the sun. Avoid tanning booths and sunlamps. Use sunscreen and wear protective clothing when outdoors. Your doctor may direct you to avoid phototherapy while you use this product. Ask your doctor for details. Azathioprine 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. Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products). 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. Tell your doctor if you are pregnant or plan to become pregnant. You should not become pregnant while using azathioprine. Azathioprine may harm an unborn baby. Ask about reliable forms of birth control while using this medication. If you become pregnant, talk to your doctor right away about the risks and benefits of this medication. This medication passes into breast milk and may have undesirable effects on a nursing infant. 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. Some products that may interact with this drug are: febuxostat, past or present use of certain cancer drugs (such as cyclophosphamide, melphalan), other drugs that weaken the immune system/increase the risk of infection (such as rituximab, tofacitinib). Azathioprine is very similar to mercaptopurine. Do not use medications containing mercaptopurine while using azathioprine.

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.