Azathioprine
1 medicine
Azathioprine is an immunosuppressant used to prevent transplant rejection and control autoimmune disease; by suppressing the immune system it raises the risk of serious infections and certain cancers, so regular blood monitoring is required.
Key facts
- Azathioprine (sold as Imuran) is an immunosuppressant: it dampens the immune system so it stops attacking a transplanted organ or the body's own tissues.
- By suppressing your immune defenses, it raises your risk of serious infections and, with long-term use, certain cancers, including skin cancers and lymphoma.
- Regular blood tests (full blood count and liver function), often weekly at first and then monthly, are required to catch dangerous drops in blood cell counts early.
- Seek urgent care for fever, sore throat, unusual bruising, or bleeding, which can signal a dangerously low white cell or platelet count.
What azathioprine treats
Azathioprine helps prevent rejection after kidney, liver, or heart transplants. It also treats autoimmune conditions where the immune system attacks the body's own tissues, including rheumatoid arthritis, inflammatory bowel disease (Crohn's disease and ulcerative colitis), and autoimmune hepatitis, usually when other treatments haven't worked well enough.
How azathioprine works
Once absorbed, azathioprine is converted in the body into compounds that get built into the DNA of rapidly dividing cells, including the immune cells that would otherwise attack transplanted tissue or the body's own organs. This slows immune cell production and calms the immune attack, but it also slows production of normal blood cells, which is why blood counts need regular checking.
Before you take it
- Tell your doctor if you've ever had testing for TPMT or NUDT15 enzyme activity; people with low activity break azathioprine down slowly and face a much higher risk of severe blood toxicity at standard doses.
- Azathioprine raises infection risk: avoid live vaccines while on treatment and tell your doctor about any fever, unusual tiredness, or infection promptly.
- It also raises long-term cancer risk, particularly skin cancers and lymphoma; use sun protection and attend skin checks.
- Discuss pregnancy plans with your doctor; azathioprine crosses the placenta, and continuing treatment in pregnancy needs specialist input.
Side effects
Common effects include nausea, loss of appetite, and mild fatigue, especially when starting treatment.
Stop and seek urgent medical care for any of these:
- Fever, chills, sore throat, or flu-like symptoms (possible serious infection or low white cell count).
- Unusual bruising or bleeding (possible low platelet count).
- Yellowing of the skin or eyes, or severe abdominal pain (possible liver injury).
- Any new or unusual skin lesion that doesn't heal.
Safety essentials
- Azathioprine's defining risk is immunosuppression: it raises the risk of serious infection and, with long-term use, certain cancers, so regular blood monitoring throughout treatment is not optional.
- Blood counts and liver function are checked before starting and at regular intervals for as long as you take it.
- Report fevers and infections early, avoid live vaccines, and use sun protection to reduce skin cancer risk.
This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.