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A thiopurine is a purine-analog medicine containing sulfur that interferes with nucleic-acid metabolism and cell proliferation. The main therapeutic thiopurines are azathioprine, mercaptopurine, and thioguanine. These medicines require metabolic conversion into active thioguanine nucleotides and other metabolites. Their effects are useful in cancer treatment and immune suppression but can also damage rapidly dividing healthy cells.
read more about thiopurine ...Mercaptopurine and thioguanine are used in selected treatment regimens for acute leukemia and related cancers. Azathioprine is used to prevent organ-transplant rejection and treat selected autoimmune or inflammatory diseases. Thiopurines are also used for maintenance treatment in some patients with inflammatory bowel disease. Approved uses and treatment protocols differ among the individual drugs.
Thiopurines are converted into metabolites that interfere with purine synthesis and can become incorporated into nucleic acids. These effects reduce DNA and ribonucleic acid production and limit proliferation of susceptible cells. Immune effects also involve changes in lymphocyte activation and survival. The balance among active and inactive metabolites helps determine effectiveness and toxicity.
Thiopurines are commonly taken orally, although selected formulations and cancer protocols use other routes. Blood counts and liver tests are checked regularly because bone-marrow suppression and liver injury can occur. Thiopurine methyltransferase and nucleotide diphosphatase 15 activity or genotype can affect dosing and severe myelotoxicity risk. Metabolite testing is used in selected patients to investigate adherence, response, or toxicity.
Important risks include low blood-cell counts, infection, bleeding, liver injury, pancreatitis, nausea, and increased risk of selected cancers with prolonged immunosuppression. People with low or absent thiopurine methyltransferase or nucleotide diphosphatase 15 activity can develop life-threatening myelosuppression at conventional doses. Allopurinol and febuxostat can markedly alter thiopurine metabolism and require avoidance or specialized dose adjustment. Fever, mouth sores, unusual bruising, severe abdominal pain, or jaundice requires prompt medical review.
Yes. Azathioprine is converted into mercaptopurine and additional metabolites in the body. It is used mainly as an immunosuppressive medicine.
Variants affecting thiopurine methyltransferase (TPMT) or nucleotide diphosphatase 15 (NUDT15) can increase active-metabolite exposure and severe bone-marrow toxicity. Results can guide starting-dose or treatment decisions.
Yes. Suppression of bone marrow and immune activity can reduce resistance to infection. Fever or other infection symptoms should be reported promptly.
The anticancer timing depends on the treatment regimen, while immune-suppressing benefits can take several weeks or months. Monitoring continues while the clinical effect develops.
Clinical Pharmacogenetics Implementation Consortium Guideline for Thiopurine Dosing Based on TPMT and NUDT15 Genotypes: 2025 Update. Clinical Pharmacology & Therapeutics (PubMed Central). https://pmc.ncbi.nlm.nih.gov/articles/PMC12997511/. Date Accessed August 6, 2026.
Azathioprine Tablets: Prescribing Information. DailyMed. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=bc6dc4bd-2121-4613-9d90-4a504010c98a. Date Accessed August 6, 2026.
Mercaptopurine Tablets: Prescribing Information. DailyMed. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e7309808-5ae8-4a55-90e3-3992ace0da62. Date Accessed August 6, 2026.
TABLOID (Thioguanine Tablets): Prescribing Information. DailyMed. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=44b0c461-47fb-4106-ba11-6ed85530235c. Date Accessed August 6, 2026.
Table of Pharmacogenetic Associations. U.S. Food and Drug Administration. https://www.fda.gov/medical-devices/precision-medicine/table-pharmacogenetic-associations. Date Accessed August 6, 2026.