Azathioprine
Azathioprine is an immunosuppressive medication that works by inhibiting the synthesis of purines, which are essential for the proliferation of immune cells. It is primarily used to prevent organ rejection after transplantation and to treat various autoimmune conditions such as rheumatoid arthritis, inflammatory bowel disease, and lupus.
Azathioprine is an immunosuppressant used to prevent organ rejection and treat autoimmune diseases by reducing immune cell proliferation.
This medication carries a boxed (black box) warning — the strongest type of FDA warning. Review the full prescribing information before use.
Key facts at a glance
- ATC
- L04AX01
- RxNorm
- 1256
- Generic
- Azathioprine
- Class
- atc-l04
- Brands
- Imuran, Azasan
- Availability
- rx
- Lactation
- unknown
- Routes
- oral
- Forms
- tablet, injection
- Regions
- US, EU, CN, JP
- Monitoring
- —
This page is for informational purposes only.
Do not use this information to diagnose yourself or to replace a physician's advice. Always consult a qualified healthcare provider before starting, stopping, or changing any medication. If you believe you are experiencing a medical emergency, call your local emergency number immediately.
Dosage and administration
- Usual dose
- 500mg twice daily
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 250mg twice daily
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 400mg daily
- Maximum
- consult physician
- Frequency
- once daily
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
Overdose information
Special Populations
8 groupspregnancy
first trimesteravoid if possible
avoid use during pregnancy unless benefits outweigh risks; discuss with healthcare provider
regular fetal monitoring, ultrasound assessments
Use of this medication in this population requires careful consideration of risks and benefits.
pregnancy
third trimesteravoid if possible
consider discontinuation before delivery; discuss with healthcare provider
fetal growth monitoring, non-stress tests
Use of this medication in this population requires careful consideration of risks and benefits.
lactation
breastfeedingdiscontinue breastfeeding
azathioprine passes into breast milk; breastfeeding not recommended
infant blood counts if exposure occurs
Use of this medication in this population requires careful consideration of risks and benefits.
geriatric
elderlyreduce starting dose by 25-50%
start at lowest effective dose; monitor closely for infections and bone marrow suppression
regular CBC monitoring, liver function tests, renal function assessment
Use with caution and monitor for adverse effects.
pediatric_age
children 2-17 yearsweight-based dosing, typically 1-2 mg/kg/day
use under specialist supervision; monitor growth and development
regular CBC, liver function tests, growth monitoring
Use with caution and monitor for adverse effects.
renal_impairment
severe renal impairmentreduce dose by 25-50%
use with caution; monitor renal function closely
frequent CBC, renal function tests, drug level monitoring if available
Use with caution and monitor for adverse effects.
hepatic_impairment
moderate to severereduce dose by 25-50%
use with caution; avoid in severe hepatic impairment if possible
frequent CBC, liver function tests, monitor for hepatotoxicity
Use with caution and monitor for adverse effects.
hepatic_impairment
mildmay require dose reduction
monitor liver function closely; adjust dose based on response and tolerability
regular liver function tests, CBC monitoring
Use with caution and monitor for adverse effects.
Statistics and clinical data
Drug class
ATC classification L04AX01
FDA approval year
Original FDA approval for Azathioprine
Common uses
Primary therapeutic applications
Mechanism of action
Pharmacological mechanism
Prevents organ rejection in transplant patients; treats autoimmune conditions including rheumatoid arthritis, inflammatory bowel disease (Crohn's disease, ulcerative colitis), systemic lupus erythematosus, and certain vasculitides.
Azathioprine is a prodrug that is converted to 6-mercaptopurine. It interferes with purine synthesis, thereby inhibiting the proliferation of T-cells and B-cells, which reduces the immune response.
Requires regular blood monitoring for bone marrow and liver function. Increases susceptibility to infections and certain cancers. Should not be used during pregnancy. May interact with allopurinol and other immunosuppressants. Complete blood counts and liver function tests are essential during treatment.
Contraindications
Conditions and patient states where this medication should be avoided or used with caution.
Do not use (1)
Known allergy to this medication or its components
Use caution (1)
Consult healthcare provider for benefits vs risks assessment
Official drug label
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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 24, 2026. · Read our editorial policy