Azathioprine (Imuran)

Azathioprine (brand name Imuran) is an immunosuppressant medication that reduces immune system activity. It's often used as a steroid-sparing agent, allowing patients to reduce their steroid dose while maintaining disease control.

How It Works

Azathioprine is converted to active metabolites that interfere with DNA synthesis, particularly in rapidly dividing cells like immune cells. This reduces immune activity and inflammation.

Common Uses

• Myasthenia gravis
• NMO and MOGAD
• Giant cell arteritis—steroid-sparing
• Other autoimmune conditions

Dosing

• Usually 1-3 mg/kg daily
• Start low, increase gradually
• Takes 3-6 months for full effect
• TPMT testing recommended before starting

Important: TPMT Testing

Side Effects

Common

• Nausea, vomiting
• Diarrhea
• Fatigue
• Increased infection risk

Serious (Monitor For)

• Bone marrow suppression (low blood counts)
• Liver problems
• Increased cancer risk (long-term)
• Severe infections

Monitoring

• Complete blood count—regularly (weekly initially, then monthly)
• Liver function tests
• Watch for signs of infection
• Report unusual bruising or bleeding

Frequently Asked Questions

Why does it take so long to work?

Azathioprine works by gradually reducing the immune cells that cause your condition. This process takes time—usually 3-6 months for significant effect.

Can I stop my steroids once I start this?

Not immediately. Azathioprine takes time to work. Your doctor will gradually taper steroids once azathioprine is effective.

Is this the same as chemotherapy?

Azathioprine is used in cancer treatment at higher doses, but for autoimmune disease, doses are lower. It still requires careful monitoring.