Imuran (azathioprine)

Imuran is a drug discovered in 1968 that weakens the immune system. Although it is mostly a drug used in kidney transplant patients to prevent the kidney being rejected, it is also used in the autoimmune diseases rheumatoid arthritis, systemic lupus erythematosus, polymyositis, ulcerative colitis and Crohn’s disease.

Each tablet can easily be broken in two, and the tablets are 50 mg. After being absorbed from the bowel it is turned in the liver into a substance called 6-mercaptopurine (6-MP). This form is also available on the market under the name Purinethol.

Imuran is not a drug of the cortisone group, but it suppresses the immune system as prednisolone does. It is not a habit-forming drug.

In inflammatory bowel diseases such as ulcerative colitis or Crohn’s disease it helps to suppress an immune system that is working too hard.

Dose and use

Imuran should be taken with food. There is no objection to taking it with milk. It is best taken as a single dose a day. One or two may be taken a day. Your doctor will adjust the dose to your weight. The aim here is the most effective treatment with the fewest side effects.

The effect of the drug will begin to be seen after three months. You may need to take this drug for several years. While taking it you should attend for follow-up and laboratory tests at set intervals.

Side effects

The benefits of using the drug over a long period matter more than the simple side effects. Rash, reduced appetite, nausea, vomiting and diarrhoea are temporary side effects and are not serious.

Side effects such as depression of the bone marrow (fever, sore throat, tiredness, weakness, abnormal bleeding and bruising of the skin), disturbance of liver function (abnormal liver tests, yellowing of the skin and eyes, darkening of the urine), pancreatitis (severe abdominal pain with nausea and vomiting) and pneumonia (cough and sputum) can be serious. When side effects are seen you should go to your doctor.

About cancers

Although some doctors think there is a rise in certain cancers such as lymphoma or Hodgkin’s disease, a study carried out at the University of Pennsylvania in 2001 on 1,467 patients with ulcerative colitis and Crohn’s disease taking Imuran found no rise in the risk of lymphoma.

For very effective adjustment of the dose, 6-MP and 6-MMP levels are now measured. A high 6-MP level causes toxicity to the bone marrow, while a high 6-MMP level causes toxicity to the liver.

Take care

Do not use Imuran if you are pregnant or planning to become pregnant soon. Birth defects have been found in animals given high doses of Imuran during pregnancy. Birth defects have also been found where the mother and the father were taking Imuran (since it affects the sperm). Breastfeeding may be inadvisable in mothers taking Imuran.

If you have a viral illness and are taking Imuran, tell your doctor, because your viral illness may worsen. If you are taking allopurinol, phenytoin, rifampicin or phenobarbital, tell your doctor, since these drugs can increase the toxicity of Imuran.