What Is Imuran? Uses, Dosage, and What You Need to Know in 2026

Imuran is the brand name for azathioprine, a prescription immunosuppressant that has been used in medicine since the 1960s. Despite being an older medication, it remains a cornerstone therapy for preventing organ transplant rejection and managing a wide range of autoimmune conditions. Here is everything you need to know about Imuran in 2026.

What Is Imuran (Azathioprine)?

Imuran (azathioprine) is an immunosuppressant in the class of medications called purine antimetabolites and disease-modifying antirheumatic drugs (DMARDs). It works by reducing the activity of the immune system — specifically by preventing T and B lymphocytes (white blood cells) from multiplying. This makes it useful both for preventing the immune system from rejecting a transplanted organ and for calming the overactive immune responses that drive autoimmune diseases.

The FDA first approved azathioprine in March 1968, making it one of the earliest immunosuppressants in clinical use. It is available as a generic under the name azathioprine (multiple manufacturers), as brand-name Imuran (50 mg tablets), and as Azasan (75 mg and 100 mg tablets).

FDA-Approved Uses for Imuran

The FDA has approved Imuran for two specific indications:

Kidney transplant rejection prevention: Imuran is used as an adjunct therapy — alongside corticosteroids and calcineurin inhibitors — to prevent the immune system from rejecting a newly transplanted kidney.

Active rheumatoid arthritis (RA): Imuran is indicated for RA to reduce signs and symptoms, typically used as a second-line DMARD after methotrexate failure or intolerance.

Common Off-Label Uses

While only approved for the two conditions above, azathioprine is widely used off-label for many other conditions, including:

Crohn's disease and ulcerative colitis (IBD) — as a steroid-sparing maintenance agent

Systemic lupus erythematosus (lupus nephritis)

Myasthenia gravis (as a steroid-sparing agent)

Autoimmune hepatitis (maintenance therapy alongside steroids)

Multiple sclerosis, neuromyelitis optica

Severe psoriasis, atopic dermatitis, pemphigus, bullous pemphigoid

Vasculitis, Behcet's disease, dermatomyositis, recurrent pericarditis

Dosage: How Much Imuran Will You Take?

Dosing varies significantly by indication and body weight:

Kidney transplant (initial): 3–5 mg/kg/day starting at the time of transplant; typically reduced to a maintenance dose of 1–3 mg/kg/day

Rheumatoid arthritis (initial): 1 mg/kg/day (typically 50–100 mg); may increase by 0.5 mg/kg every 4 weeks up to a maximum of 2.5 mg/kg/day

Doses for off-label uses vary. The most common tablet strength is 50 mg, taken once or twice daily depending on your total daily dose. Imuran should generally be taken with food to reduce nausea.

How Long Does It Take Imuran to Work?

Imuran is a slow-acting medication. For rheumatoid arthritis, it typically takes 6–8 weeks to see initial response and up to 12 weeks to experience the full benefit. If there is no improvement after 12 weeks at the maximum tolerated dose, your doctor may consider the medication ineffective and discuss alternatives. This slow onset is one reason azathioprine should never be stopped abruptly — it needs to be taken consistently over time to maintain its effect.

Is Imuran a Controlled Substance?

No. Imuran (azathioprine) is not a controlled substance and is not scheduled by the DEA. It requires a standard prescription and cannot be refilled without a new prescription in states with annual prescription limits, but there are no special DEA-imposed restrictions on prescribing, dispensing, or possession.

For a deeper explanation of how azathioprine works at the molecular level, see our article How Does Imuran Work? If you're struggling to find Imuran at your pharmacy, medfinder can help you locate a pharmacy near you that has it in stock.