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GSK / Imuran
How does it work?
Imuran tablets and injection contain the active ingredient azathioprine, which is a type of medicine called an immunosuppressant. (NB. Azathioprine tablets are also available without a brand name, ie as the generic medicine.) Azathioprine is used to dampen down the activity of cells in the immune system.
The immune system normally recognises and protects the body from foreign substances such as bacteria and viruses. It also recognises and attacks transplanted tissue and cells that have become cancerous.
Sometimes however, the immune system can react excessively, or mount an attack against normal healthy tissues. This can result in various disorders known as autoimmune diseases. For example, in rheumatoid arthritis the immune system attacks the joints, causing pain and inflammation. In systemic lupus erythematosus the immune system attacks the skin and internal organs. The activity of the immune system can also be a problem following organ transplants, because it recognises the transplanted tissue as foreign and attacks it, causing the organ to be rejected. In situations such as these it is useful to suppress the activity of the immune system.
The immune system relies on different types of white blood cells that are produced in the bone marrow and lymph glands. Azathioprine works by decreasing the production of these white blood cells. It does this by interfering with the production of the cells genetic material, DNA, which stops the cells from dividing and multiplying.
The decrease in the numbers of white blood cells reduces the ability of the immune system to reject organ transplants. In autoimmune diseases it reduces the immune system attack on normal tissues and so reduces the severity of the symptoms, and in many cases halts the progress of the disease. However, it can take weeks to months of treatment for the full effect of the medicine to become apparant.
Unfortunately white blood cells are needed to fight invading micro-organisms, so during treatment the body becomes more susceptible to infections. Azathioprine also interferes with the growth and division of other types of blood cells in the bone marrow. Reduced production of red blood cells can cause anaemia and reduced production of platelets can cause problems with blood clotting. For this reason, your doctor will monitor the levels of all your blood cells.
Azathioprine is often used in combination with other immunosuppressants such as corticosteroids. When combined with corticosteroids it can often allow a reduced dose of corticosteroid to be used.
What is it used for?
- Abnormal destruction of liver cells by the body's immune system (active chronic autoimmune hepatitis)
- Abnormal destruction of red blood cells by the body's immune system (autoimmune haemolytic anaemia)
- Blistering skin disorder caused by abnormal attack of the skin cells by the body's immune system (pemphigus vulgaris)
- Abnormal destruction of blood platelets by the body's immune system (chronic idiopathic thrombocytopenic purpura)
- Inflammatory disease of the skin and muscles (dermatomyositis)
- Inflammatory disease of the muscles (polymyositis)
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