Azathioprine Dosage

Medically reviewed by Drugs.com. Last updated on Jan 27, 2025.

Usual Adult Dose for Renal Transplant

Initial dose: 3 to 5 mg/kg orally or IV once a day, beginning at the time of transplant
Maintenance dose: 1 to 3 mg/kg orally or IV once a day

Comments:

• In a minority of cases, therapy has been started 1 to 3 days before transplantation
• The dose should not be increased to toxic levels because of threatened rejection

Use: Adjunctive therapy for prevention of rejection in renal homotransplantation.

Usual Adult Dose for Rheumatoid Arthritis

Initial dose: 1 mg/kg (50 to 100 mg) orally or IV per day given in 1 to 2 divided doses
Maintenance dose: Lowest effective dose
Maximum dose: 2.5 mg/kg orally or IV per day
Duration: At least 12 weeks

Comments:

• Dose may be increased by 0.5 mg/kg/day (or approximately 25 mg/day), after 6 to 8 weeks of starting treatment and thereafter at 4 week intervals if necessary.
• Gradual dose reduction is recommended to reduce the risk of toxicities.
• Therapeutic response occurs after several weeks of therapy, usually 6 to 8 weeks. Patients not improved after 12 weeks can be considered refractory.
• Azathioprine may be continued long-term in patients with clinical response.

Usual Adult Dose for Crohn's Disease - Acute

Studies:
1.5 to 4 mg/kg per day for 10 days up to 52 weeks

Usual Adult Dose for Crohn's Disease - Maintenance

Studies:
1.5 to 4 mg/kg per day for 10 days up to 52 weeks

Usual Adult Dose for Chronic Inflammatory Demyelinating Polyradiculoneuropathy

Study (n=14)
2 to 3 mg/kg orally once a day for 9 months

Usual Adult Dose for Atopic Dermatitis

Study (n=37)
2.5 mg/kg orally once a day, in the morning, for 3 months

Usual Adult Dose for Sarcoidosis

Study (n=11)
Initial dose: 2 mg/kg per day in combination with prednisolone 0.6 to 0.8 mg/kg per day, with prednisolone reduced to 0.1 mg/kg within 2 to 3 months
Maintenance dose: 2 mg/kg per day with prednisolone 0.1 mg/kg per day for 21 to 22 months

Usual Adult Dose for Ulcerative Colitis

Study (n=9)
IV: 20 to 40 mg/kg via IV infusion over 36 hours or 40 mg/kg as three 8-hour infusions over 3 days followed by oral azathioprine
Oral: 2 mg/kg orally per day beginning the day after completion of the IV loading dose

Study (n=12)
50 mg per day for 2 weeks, then 2 to 2.5 mg/kg per day plus mesalamine 500 mg orally 3 times a day; these drugs were started immediately after signs of remission was achieved (mean: 14.5 days) with cyclosporine IV (4 mg/kg/day)

Usual Adult Dose for Uveitis

Study (n=14)
Treatment of choroidal neovascularization: 1 to 1.5 mg/kg orally per day, in combination with prednisolone and cyclosporine

Usual Adult Dose for Multiple Sclerosis

Study (n=6)
Patients refractory to interferon beta-1b:
Initial dose: Azathioprine should be titrated up to 1.5 mg/kg per day over 1 month, followed by 50 mg increments in 6-month intervals, concomitantly with 8 million international units subcutaneous interferon beta-1b on alternate days
Maintenance dose: 2 mg/kg per day

Usual Adult Dose for Systemic Lupus Erythematosus

Studies:
1 to 3 mg/kg actual body weight (ABW)/day orally or IV once a day

Study (n=55)
Diffuse proliferative lupus glomerulonephritis: Sequential therapy starting with prednisone (1 mg/kg/day) for 8 to 10 weeks, gradually tapering to maintenance dosage of 5 to 10 mg/day, together with oral cyclophosphamide (1 to 2 mg/kg/day) for 6 to 9 months followed by azathioprine 50 to 100 mg/day

Usual Adult Dose for Chronic Active Hepatitis

Study (n=72)
Autoimmune hepatitis: 1 to 2 mg/kg per day, concomitantly with prednisolone (5 to 15 mg/day) for a minimum of 1 year (average 5 years)

Usual Adult Dose for Takayasu's Arteritis

Study (n=15)
2 mg/kg ABW/day for 1 year in combination with prednisolone taper

Usual Pediatric Dose for Atopic Dermatitis

Study (n=37)
Greater than 17 years: 2.5 mg/kg orally once a day, in the morning, for 3 months

Usual Pediatric Dose for Organ Transplant - Rejection Prophylaxis

Initial dose: 3 to 5 mg/kg orally or IV once a day, beginning at the time of transplant
Maintenance dose: 1 to 3 mg/kg orally or IV once a day

Usual Pediatric Dose for Eczema

Study (n=91)
Greater than 6 years: 2.5 to 3.5 mg/kg per day in patients with normal levels of thiopurine methyltransferase

Usual Pediatric Dose for Systemic Lupus Erythematosus

Case Study (n=67)
Lupus Nephritis:
Greater than 5 years: 2 to 3 mg/kg per day (maximum dose: 150 mg/day)
Dose should be titrated to maintain a total white blood cell count between 3 and 4 x 10(3) cells/mL.

Renal Dose Adjustments

Lower doses may be required; however, no specific guidelines have been suggested.

Liver Dose Adjustments

Dose adjustments may be required; however, no specific guidelines have been suggested.

Dose Adjustments

Dosage reduction or alternative therapy may be required in patients with reduced thiopurine S-methyltransferase (TPMT) activity.

Concomitant allopurinol: Azathioprine dose should be reduced to 25% to 33% of the usual dose. Further dose reduction or alternative therapies should be considered for patients with low or absent TPMT activity.

Precautions

US BOXED WARNING(S):

• Chronic immunosuppression with azathioprine increases the risk of malignancy.
• Post-transplant lymphoma and hepatosplenic T-cell lymphoma (HSTCL) has been reported in patients with inflammatory bowel disease.

Recommendations:

• Inform patients of the risk of malignancy with azathioprine.

Consult WARNINGS section for additional precautions.

Dialysis

Data not available; approximately 45% of an azathioprine dose is removed by hemodialysis.

Other Comments

Administration advice:

• IV: Doses should generally be infused over 30 to 60 minutes; it may be administered over 5 minutes and, for the daily dose, over 8 hours

Reconstitution/preparation techniques: The manufacturer product information should be consulted

Storage requirements:

• IV: Once reconstituted, the solution for injection should be used within 24 hours

General:

• TPMT testing may be required in patients with abnormal CBC results that do not respond to dose reduction
• Treatment cessation may be required for severe hematologic or other toxicity
• Appropriate handling procedures for immunosuppressive agents according to local guidelines should be considered

Monitoring:

• Hematologic: CBC, including platelet count, weekly for the first month, twice a month for the second and third months, then once a month or more often if necessary
• Hepatic: Liver function
• Immunologic: Signs and symptoms of infection

Patient advice:

• Minimize exposure to sunlight and UV light by wearing protective clothing and using a sunscreen with a high protection factor
• Report any unusual bleeding or bruising, or signs and symptoms of infection

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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