Imuran

Imuran (azathioprine) is an immunosuppressive antimetabolite medication indicated for the management of autoimmune disorders and the prevention of organ transplant rejection. As a prodrug of 6-mercaptopurine, it exerts its therapeutic effects by interfering with purine synthesis, thereby inhibiting the proliferation of lymphocytes and modulating overactive immune responses. Its established efficacy and well-characterized safety profile make it a cornerstone in long-term immunomodulatory therapy, particularly in rheumatology, gastroenterology, and transplant medicine. Proper patient selection, dosing, and monitoring are critical to maximizing therapeutic outcomes while minimizing associated risks.

Features

• Active ingredient: Azathioprine
• Available formulations: Oral tablets (25 mg, 50 mg, 75 mg, 100 mg)
• Mechanism: Purine analogue antimetabolite; inhibits DNA/RNA synthesis
• Prodrug status: Converted in vivo to active metabolites 6-mercaptopurine and 6-thioinosinic acid
• TPMT enzyme-dependent metabolism: Requires pre-treatment genotyping/phenotyping
• Delayed onset of action: Full therapeutic effect may take 8–12 weeks

Benefits

• Provides targeted suppression of cell-mediated immunity, reducing autoimmune activity and inflammation
• Enables corticosteroid dose reduction or discontinuation in steroid-dependent conditions
• Demonstrates proven efficacy in maintaining remission in chronic autoimmune disorders
• Supports long-term graft survival in renal and other solid organ transplants
• Offers flexible dosing adjusted to individual tolerance and therapeutic response
• Well-established in clinical guidelines with decades of real-world evidence

Common use

Imuran is commonly prescribed for autoimmune conditions such as rheumatoid arthritis, systemic lupus erythematosus, inflammatory bowel disease (including Crohn’s disease and ulcerative colitis), autoimmune hepatitis, and certain dermatological disorders like pemphigus vulgaris. In transplant medicine, it is used as an adjunct immunosuppressant to prevent acute and chronic rejection in kidney, heart, and liver transplant recipients. It may also be used off-label in other immune-mediated conditions under specialist supervision.

Dosage and direction

Dosing is highly individualized based on indication, patient weight, renal function, and TPMT enzyme activity. For autoimmune diseases, the initial dose is typically 1–3 mg/kg/day orally, often starting at the lower end with gradual titration. In transplant protocols, doses range from 3–5 mg/kg/day initially, often reduced to maintenance doses of 1–3 mg/kg/day. Tablets should be taken with food to minimize gastrointestinal upset. Regular monitoring of complete blood count and liver function is mandatory, especially during dose escalation.

Precautions

Patients should be advised that Imuran increases susceptibility to infections and may predispose to malignancies such as lymphoma and skin cancer. Live vaccines are contraindicated during therapy. It is imperative to assess thiopurine methyltransferase (TPMT) activity prior to initiation to identify patients at high risk for myelosuppression. Use with caution in patients with renal impairment, hepatic disease, or those taking other myelosuppressive agents. Pregnancy should be avoided unless benefits outweigh risks (Pregnancy Category D).

Contraindications

Imuran is contraindicated in patients with known hypersensitivity to azathioprine or any component of the formulation. It should not be used in patients who have previously exhibited severe bone marrow suppression on thiopurine therapy. Patients with absent TPMT activity should not receive this drug due to extreme risk of fatal pancytopenia. Concurrent use with live vaccines is contraindicated.

Possible side effect

Common side effects include nausea, vomiting, diarrhea, leukopenia, thrombocytopenia, and mild hepatic enzyme elevations. Serious adverse reactions may include severe bone marrow suppression (pancytopenia), hepatotoxicity, pancreatitis, and increased susceptibility to opportunistic infections. Long-term use is associated with increased risk of lymphoproliferative disorders and non-melanoma skin cancers. Macrocytosis is frequently observed and does not necessarily require discontinuation.

Drug interaction

Allopurinol potently inhibits xanthine oxidase, leading to dangerously increased levels of active metabolites—dose reduction of Imuran by ⅔ to ¾ is mandatory if co-administered. ACE inhibitors may increase the risk of anemia and leukopenia. Warfarin efficacy may be reduced. Other myelosuppressive agents (e.g., sulfamethoxazole-trimethoprim) can compound hematologic toxicity. Live vaccines should be avoided.

Missed dose

If a dose is missed, it should be taken as soon as remembered unless it is nearly time for the next dose. Doubling the dose to make up for a missed dose is not recommended. Patients should contact their healthcare provider if multiple doses are missed for guidance on resumption.

Overdose

Overdose manifests primarily as hematologic toxicity—severe leukopenia, thrombocytopenia, and bleeding. Nausea, vomiting, diarrhea, and hepatic dysfunction may occur. Management is supportive, including hospitalization, blood product transfusions, and aggressive infection prophylaxis. Hemodialysis is not effective due to high protein binding and extensive tissue distribution.

Storage

Store at room temperature (20–25°C/68–77°F) in a dry place, protected from light and moisture. Keep in the original container and out of reach of children. Do not use beyond the expiration date printed on the packaging.

Disclaimer

This information is intended for educational purposes and does not replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before starting or changing any medication regimen. Individual patient responses and risks may vary.

Reviews

Clinical studies and long-term observational data consistently support the efficacy of Imuran in maintaining remission in autoimmune diseases and preventing transplant rejection. Specialist consensus emphasizes its role as a valuable steroid-sparing agent. Patient-reported outcomes highlight improved quality of life despite the need for vigilant monitoring. Its well-predictable pharmacokinetics and dose-response relationship contribute to its enduring use in immunology and transplantation.