| Item |
Information |
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Drug Groups
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approved |
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Description
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An immunosuppressive pro-drug. It is converted into 6-mercaptopurine in the body where it blocks purine metabolism and DNA synthesis. |
| Indication |
For use in rheumatoid arthritis, preventing renal transplant rejection, Crohn's disease, and colitis. |
| Pharmacology |
Azathioprine is a chemotherapy drug, now rarely used for chemotherapy but more for immunosuppression in organ transplantation and autoimmune disease such as rheumatoid arthritis or inflammatory bowel disease or Crohn's disease. It is a pro-drug, converted in the body to the active metabolite 6-mercaptopurine. Azathioprine acts to inhibit purine synthesis necessary for the proliferation of cells, especially leukocytes and lymphocytes. It is a safe and effective drug used alone in certain autoimmune diseases, or in combination with other immunosuppressants in organ transplantation. Its most severe side effect is bone marrow suppression, and it should not be given in conjunction with purine analogues such as allopurinol. The enzyme thiopurine S-methyltransferase (TPMT) deactivates 6-mercaptopurine. Genetic polymorphisms of TPMT can lead to excessive drug toxicity, thus assay of serum TPMT may be useful to prevent this complication. |
| Toxicity |
The oral LD50 for single doses of azathioprine in mice and rats are 2500 mg/kg and 400 mg/kg, respectively. Very large doses of this antimetabolite may lead to marrow hypoplasia, bleeding, infection, and death. |
| Affected Organisms |
| • |
Humans and other mammals |
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| Biotransformation |
Primarily converted to the active metabolites 6-mercaptopurine and 6-thioinosinic acid via a non-enzymatica process. 6-mercaptopurine is subsequently metabolized primarily by xanthine oxidase. |
| Absorption |
Well absorbed following oral administration. |
| Half Life |
Approximately 5 hours for the unchanged drug and its metabolites. |
| Protein Binding |
Azathioprine and the metabolite mercaptopurine are moderately bound to serum proteins (30%). |
| References |
| • |
Konstantopoulou M, Belgi A, Griffiths KD, Seale JR, Macfarlane AW: Azathioprine-induced pancytopenia in a patient with pompholyx and deficiency of erythrocyte thiopurine methyltransferase. BMJ. 2005 Feb 12;330(7487):350-1.
[Pubmed]
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Woodroffe R, Yao GL, Meads C, Bayliss S, Ready A, Raftery J, Taylor RS: Clinical and cost-effectiveness of newer immunosuppressive regimens in renal transplantation: a systematic review and modelling study. Health Technol Assess. 2005 May;9(21):1-179, iii-iv.
[Pubmed]
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| • |
Gombar VK, Enslein K, Blake BW: Carcinogenicity of azathioprine: an S-AR investigation. Mutat Res. 1993 May;302(1):7-12.
[Pubmed]
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| External Links |
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