What are the main side effects to be feared if you take immunosuppressants for a long time?

Immunosuppressants have multiple side effects, some of which differ depending on the immunosuppressant. Always refer to the information sheet placed in the medicine packet, and ask your doctor for advice if you have any doubt.

The risk of infection

The most feared side effect when prescribing an immunosuppressant is the increased risk of infection. This risk is directly related to the mechanism of action of immunosuppressants, which decrease the number and activity of white blood cells. These white blood cells are the main therapeutic target of immunosuppressants during lupus, as they are over-activated during the autoimmune process that underlies this disease. The problem is that immunosuppressants decrease the number of white blood cells, without differentiating between the "good" white blood cells, which protect against infections, and the "bad" ones, which are "responsible" for lupus. The stronger the immunosuppressant, the greater this risk.

Immunosuppressants act in addition to corticosteroids and allow corticosteroid doses to be reduced. Corticosteroids are also themselves providers of infections and reducing the dose therefore ultimately reduces this risk a little.

The risk of lower blood cell levels Immunosuppressants inhibit the proliferation of rapidly multiplying cells, such as white or red blood cells and platelets. They can, therefore, block the growth of other components of the blood and promote the development of anemia (decrease in red blood cells), thrombocytopenia (decrease in platelets) or leukopenia (decrease in white blood cells). This risk justifies regular monitoring of the blood count (determination of the number of white and red blood cells as well as platelets in the blood).

The risk of sterility

It is to be taken into consideration for cyclophosphamide. This risk increases with the total amount of cyclophosphamide being received and the age of the person when treatment is started. It concerns men and women. Use consistent with the age of the patient and perhaps use of other drugs can reduce this risk.

The teratogenic risk (fetal malformations) exists for most of them, with the exception of azathioprine.

These treatments will therefore be interrupted by your doctor during pregnancy.

The risk of cancer

The risk of cancer is a low long-term risk, but must be prevented. Several mechanisms are involved:

decreased body defences against cancer cells or against certain viruses that facilitate the cancerization process (papillomavirus for the cervical cancer, Epstein-Barr virus for lymphomas);

direct toxicity of the immunosuppressant or some of these catabolites (bladder cancers favoured by cyclophosphamide). This toxicity is extremely rare and can be prevented by the use of uromitexan. It may be promoted by exposure to other risk factors such as prolonged sun exposure in patients treated with azathioprine.  Immunosuppressants used in systemic lupus do not increase the risk of lymphoma. Lupus on its own, without treatment, is associated with a slightly increased risk of lymphoma, like many other autoimmune diseases. In fact, immunosuppressants may even decrease the risk of lymphoma by "calming" lymphocytes.


The most worrisome side effect, when taking an immunosuppressant, is the increased risk of infection which is directly related to the mechanism of action of these molecules (decrease in white blood cells). Immunosuppressants also block the growth of certain components in the blood, and therefore promote the development of anemia (decrease in red blood cells) or thrombocytopenia (decrease in platelets) and leukopenia (decrease in white blood cells). This risk justifies regular monitoring of the blood count (count of white and red blood cells, as well as platelets in the blood). Finally, in the long run, some immunosuppressants could expose one to an increased risk of cancers, but not lymphoma.

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