How Imuran Works

Imuran (azathioprine) is a prodrug of mercaptopurine (6-MP). Prodrugs are drugs that convert inside the body into other active drugs. This means that after Imuran is taken, it is converted to the active drug mercaptopurine inside the body.

Mercaptopurine inhibits an enzyme that is required for the synthesis, or creation, of DNA. This effect reduces the numbers of cells that can rapidly replicate in the body, including the immune system’s white blood cells: T-cells and B-cells. This effect also explains some of Imuran’s possible side effects because other types of cells can be impacted as well.

Although suppressing the immune system can make it slightly harder for patients to fight off infections, it also helps stabilizes an overactive immune system. Patients suffering from rheumatic diseases like lupus or arthritis will notice a reduction in their symptoms as their immune system’s attack on their own body is weakened.

Side Effects of Imuran

Imuran is a powerful medicine that requires regular blood tests to monitor for more serious side effects to the liver and bone marrow. Patients are advised to stop drinking alcohol while taking Imuran to help protect the liver.

MORE COMMON side-effects include:

  • Nausea, vomiting, and diarrhea – Patients should tell their doctor if this happens
  • Skin rash that may be itchy – Patients should let their doctor know if they develop a rash while taking Imuran
  • Aching in the joints

RARE side-effects include:

  • Hair Loss – Imuran rarely causes thinning of the hair. Patients should let their doctor know if this becomes a problem.
  • Liver – Imuran may irritate the liver. This does not usually cause symptoms but can be found on blood tests. This is uncommon and any damage is usually reversible when patients are regularly monitored with monthly blood tests.
  • Blood Counts – Imuran can cause a drop in the numbers of red blood cells (which carry oxygen), white blood cells (which are needed to fight infection) and platelets (which help to stop bleeding). Any changes in blood counts will be caught with regular blood tests.
  • Infection – Any infections or fevers should be taken seriously and reviewed by a doctor.
  • Malignancy – Malignancy – When used for long periods of time, Imuran may be associated with a small increased risk of skin or blood cancers.

How to minimize the side-effects of Imuran:

  • Patients should take Imuran as prescribed and get regular blood tests
  • Patients should attend all doctor appointments
  • Taking Imuran with food helps reduce possible stomach upset
  • Patients should avoid alcohol while taking Imuran

Patients should talk to their doctor if they are concerned about any side effects.

Imuran can safely be stopped without needing to be weaned off. However, rheumatic diseases can “flare” after the medicine is stopped.

Imuran is not considered safe in pregnancy or breastfeeding.

Who Should NOT Take Imuran

People who should NOT be taking Imuran include:

  • Patients who have had a previous reaction to Imuran
  • Men who are planning pregnancy with their partner
  • Some patients with diseases of the liver, kidney, or blood disorders
  • Patients with active infections

Anyone who becomes pregnant while taking Imuran should notify their doctor.

When to Call a Doctor

People taking Imuran should call their doctor if they feel sick and want to stop, or they are concerned about any side effects.

Other reasons to call a doctor while taking Imuran include:

  • Nausea or diarrhea
  • Fever or possible infection
  • Rash
  • Stomach pain or noticing yellowing of the skin
  • Becoming pregnant or planning pregnancy
  • Before any surgery

Imuran Video

Watch Dr. Andy Thompson, a Canadian rheumatologist, introduce Imuran.