What is "azathioprine"

n. (context pharmacology English) An immunosuppressant used in organ transplant and autoimmune diseases to prevent rejection.

n. an immunosuppressive drug (trade name Imuran) used to prevent rejection of a transplanted organ [syn: Imuran]

Azathioprine (AZA), also known by its brand name Imuran, is an immunosuppressive drug used in organ transplantation and autoimmune diseases and belongs to the chemical class of purine analogues. Synthesized originally as a cancer drug and a prodrug for mercaptopurine in 1957, it has been widely used as an immunosuppressant for more than 50 years.

Azathioprine is an imidazolyl derivative and prodrug of mercaptopurine. In vivo, the metabolites of mercaptopurine are incorporated into replicating DNA, halting replication, as well as blocking the pathway for purine synthesis. It thus most strongly affects proliferating cells, such as the T cells and B cells of the immune system.

The main adverse effect of azathioprine is bone marrow suppression, which can be life-threatening, especially in people with a genetic deficiency of the enzyme thiopurine S-methyltransferase. The 6-thioguanine nucleotide metabolites appear to mediate the majority of azathioprine’s immunosuppressive and toxic effects. It is listed by the International Agency for Research on Cancer as a group 1 carcinogen (carcinogenic to humans).

Azathioprine is produced by a number of manufacturers under different brand names. It is on the World Health Organization's List of Essential Medicines, a list of the most important medication needed in a basic health system.