Imuran (azathioprine) is an immunosuppressive antimetabolite medication primarily used to prevent organ transplant rejection and manage active autoimmune disorders. As a prodrug of 6-mercaptopurine, it works by inhibiting purine synthesis, thereby suppressing DNA and RNA production and reducing proliferation of immune cells. This mechanism makes it valuable for controlling inappropriate immune responses in conditions like rheumatoid arthritis, lupus, and inflammatory bowel disease. Proper therapeutic monitoring and dosage individualization are essential for optimizing outcomes while minimizing adverse effects.

Features

• Contains azathioprine as the active pharmaceutical ingredient
• Available in 25 mg, 50 mg, 75 mg, and 100 mg scored tablets
• Oral administration with bioavailability approximately 47%
• Metabolized primarily to active metabolites 6-mercaptopurine and 6-thioinosinic acid
• Requires hepatic activation via hypoxanthine-guanine phosphoribosyltransferase
• Eliminated primarily renal (46%) with half-life of approximately 5 hours

Benefits

• Effectively reduces risk of organ transplant rejection when used in combination regimens
• Provides steroid-sparing effect in autoimmune conditions, reducing corticosteroid dependence
• Modifies disease progression in rheumatoid arthritis and other autoimmune disorders
• Offers oral administration convenience compared to biologic alternatives
• Established long-term safety profile with decades of clinical use
• Cost-effective immunosuppressive option compared to newer biologic agents

Common use

Imuran is indicated for prevention of rejection in renal homotransplantation, typically as part of a combination immunosuppressive regimen with corticosteroids and other agents. In autoimmune conditions, it is used for management of severe, active rheumatoid arthritis unresponsive to conventional therapies, systemic lupus erythematosus, autoimmune hepatitis, inflammatory bowel disease (including Crohn’s disease and ulcerative colitis), and certain dermatological conditions like pemphigus vulgaris. The medication is generally reserved for cases where conventional treatments have proven inadequate or caused unacceptable side effects.

Dosage and direction

Dosage must be individualized based on patient weight, clinical condition, and tolerance. For renal transplantation: initial dose is usually 3-5 mg/kg daily, then maintenance dose of 1-3 mg/kg daily. For rheumatoid arthritis: initial dose is approximately 1.0 mg/kg (50-100 mg) daily as single or divided dose, may increase by 0.5 mg/kg after 6-8 weeks, maximum 2.5 mg/kg daily. Should be administered with food to minimize gastrointestinal upset. Regular blood count monitoring is essential, with dosage adjustments based on laboratory parameters and clinical response. Patients should be advised to take Imuran at the same time each day to maintain consistent blood levels.

Precautions

Complete blood counts must be monitored weekly during first month, twice monthly for second and third months, then monthly thereafter. Liver function tests should be performed regularly. Patients should be advised to report any signs of infection, unusual bleeding, or bruising immediately. Use with caution in patients with impaired renal function, requiring dosage reduction. May cause fetal harm; women of childbearing potential should use effective contraception. Vaccination may be less effective during therapy; live vaccines should generally be avoided. Increased risk of secondary malignancies, particularly skin cancer—regular dermatological examinations recommended. Patients should use sun protection measures diligently.

Contraindications

Hypersensitivity to azathioprine or any component of the formulation. Treatment of rheumatoid arthritis in pregnant women. Patients with rheumatoid arthritis who have been treated with alkylating agents (cyclophosphamide, chlorambucil, melphalan, others) may have a prohibitive risk of neoplasia with Imuran therapy. Should not be used in patients with absolute neutrophil count below 1,500/mm³ or platelet count below 75,000/mm³. Contraindicated in patients with known deficiency of thiopurine methyltransferase (TPMT) activity, as this significantly increases risk of severe myelosuppression.

Possible side effect

Common (≥1%): Leukopenia, thrombocytopenia, macrocytic anemia, nausea, vomiting, diarrhea, anorexia, fever, rash, alopecia. Serious but less common: Severe bone marrow suppression (may be delayed), hepatotoxicity (elevated transaminases, cholestatic jaundice), pancreatitis, increased susceptibility to infections (including opportunistic infections), gastrointestinal ulceration, pneumonitis. Long-term concerns: Increased risk of neoplasia, particularly non-Hodgkin lymphoma and skin cancers. Hypersensitivity reactions including Stevens-Johnson syndrome, toxic epidermal necrolysis, and drug reaction with eosinophilia and systemic symptoms (DRESS) have been reported.

Drug interaction

Allopurinol markedly potentiates Imuran’s effects and toxicity by inhibiting xanthine oxidase—dose reduction to 25-33% of usual dose is required. Angiotensin-converting enzyme inhibitors may increase risk of anemia. Warfarin effect may be reduced. May decrease effectiveness of neuromuscular blocking agents. Other myelosuppressive agents (including sulfasalazine, trimethoprim/sulfamethoxazole) may increase risk of hematologic toxicity. Live vaccines should be avoided due to theoretical risk of vaccine-induced disease.

Missed dose

If a dose is missed, it should be taken as soon as remembered unless it is almost time for the next dose. In that case, skip the missed dose and resume the regular dosing schedule. Do not double the dose to make up for a missed dose. Patients should be advised to maintain a consistent dosing schedule and contact their healthcare provider if multiple doses are missed for guidance on resumption of therapy.

Overdose

Symptoms may include nausea, vomiting, diarrhea, and hematologic toxicity including leukopenia, thrombocytopenia, and anemia. May also present with liver function abnormalities and increased susceptibility to infections. There is no specific antidote. Management includes immediate discontinuation of the drug, supportive care, and aggressive treatment of complications. Hematologic monitoring should be instituted and maintained until blood counts recover. Transfusions may be necessary for severe cytopenias. Dialysis is not effective due to high protein binding and extensive tissue distribution.

Storage

Store at controlled room temperature 20°-25°C (68°-77°F). Keep container tightly closed. Protect from light and moisture. Keep out of reach of children and pets. Do not use after expiration date printed on packaging. Do not transfer tablets to other containers as this may affect stability. Properly dispose of any unused medication according to local regulations.

Disclaimer

This information is for educational purposes only and does not constitute medical advice. Treatment decisions should be made by qualified healthcare professionals based on individual patient circumstances. The prescribing physician should be consulted for specific dosing recommendations and monitoring parameters. Patients should not alter their medication regimen without medical supervision. While every effort has been made to ensure accuracy, medical knowledge evolves and the most current prescribing information should always be consulted.

Reviews

Clinical studies demonstrate Imuran’s efficacy in transplant rejection prevention, with one-year graft survival rates of 85-90% when used in combination regimens. In rheumatoid arthritis, approximately 60-70% of patients show meaningful clinical improvement, with steroid dose reduction achieved in most responsive patients. Gastroenterologists report sustained remission in approximately 50-60% of inflammatory bowel disease patients. The main limitations noted in clinical experience include the delayed onset of action (typically 6-12 weeks for full effect) and the need for vigilant laboratory monitoring. Most specialists consider it a valuable option in the immunosuppressive arsenal, particularly for maintenance therapy.