Azathioprine is used to prevent organ rejection in people who have received a kidney transplant. It is usually taken along with other medications to allow your new kidney to function normally. Azathioprine is also used to treat rheumatoid arthritis. In this condition, the body's defense system (immune system) attacks healthy joints. Azathioprine belongs to a class of drugs known as immunosuppressants. It works by weakening the immune system to help your body accept the new kidney as if it were your own (in the case of an organ transplant) or to prevent further damage to your joints (in the case of rheumatoid arthritis).

Talk to your doctor about the risks and benefits of azathioprine, especially when used by children and young adults.

This section contains uses of this drug that are not listed in the approved professional labeling for the drug but that may be prescribed by your health care professional. Use this drug for a condition that is listed in this section only if it has been so prescribed by your health care professional.

This drug may also be used to reduce the risk of rejection of other transplanted organs. It may also be used for certain types of bowel conditions (Crohn's disease, ulcerative colitis), and other immune system problems.

Take this medication by mouth as directed by your doctor, usually once or twice daily. Take this medication with food to reduce stomach upset.

The dosage is based on your medical condition, weight, and response to treatment. Do not increase your dose or use this drug more often or for longer than prescribed. Your condition will not improve any faster, and your risk of serious side effects will increase.

Use this medication regularly to get the most benefit from it. To help you remember, take it at the same time(s) each day.

For the treatment of arthritis, it may take up to 2 months before your symptoms get better. Tell your doctor if your condition does not get better after 3 months of treatment.

Since this drug can be absorbed through the skin and lungs and may harm an unborn baby, women who are pregnant or who may become pregnant should not handle this medication or breathe the dust from the tablets.

See also Warning section.

Nausea or vomiting may occur. Taking 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, you have been prescribed this drug because your doctor 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.

Before taking 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
• certain enzyme disorders (TPMT deficiency, NUDT15 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 make current infections worse. Stay away from anyone who has an infection that may easily spread (such as chickenpox, COVID-19, measles, flu). Talk to 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).

Tell your health care professional that you are using azathioprine before having any immunizations/vaccinations. 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.

Since this drug can be absorbed through the skin and lungs and may harm an unborn baby, women who are pregnant or who may become pregnant should not handle this medication or breathe the dust from the tablets.

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 breastfeeding.

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.

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 1-800-222-1222. Canada residents can call 1-844-764-7669.

Do not share this medication with others.

Lab and/or medical tests (such as complete blood count, liver/kidney function) should be done while you are taking this medication. Keep all medical and lab appointments. Consult your doctor for more details.

If you have had an organ transplant, attend a transplant education class or support group. Learn the symptoms of organ rejection such as a feeling of being ill, fever, pain around the transplanted organ, and the signs of a failing transplanted organ (a decrease in the amount of urine with kidney transplant). Get medical help right away if these symptoms occur.

If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.

Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.

Your condition can cause complications in a medical emergency. For information about enrolling in MedicAlert, call 1-888-633-4298 (US) or 1-800-668-1507 (Canada).