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Oral formulations of azathioprine

Drugs List

  • azathioprine 25mg tablets
  • azathioprine 50mg tablets
  • IMURAN 25mg tablets
  • IMURAN 50mg tablets
  • Therapeutic Indications


    Autoimmune disease
    Crohn's disease
    Transplant rejection - prevention of
    Ulcerative colitis

    Adjunctive treatment with corticosteroids and/or other immunosuppressive agents and procedures to enhance the survival of organ transplants such as renal, cardiac and hepatic transplants.

    Adjunctive treatment to reduce the corticosteroid requirements of renal transplant recipients.

    Either alone or as adjunctive treatment with corticosteroids and/or other drugs and procedures in a proportion of patients with the following conditions:
    -Severe rheumatoid arthritis
    -Systemic lupus erythematous
    -Dermatomyositis and polymyositis
    -Auto-immune chronic active hepatitis
    -Pemphigus vulgaris
    -Polyarteritis nodosa
    -Auto-immune haemolytic anaemia
    -Chronic refractory idiopathic thrombocytopenia purpura
    -Pyoderma gangrenosa

    -Severe or moderately severe inflammatory intestinal disease (Crohn's disease or ulcerative colitis)

    Unlicensed Uses

    Severe refractory eczema

    Treatment of severe refractory eczema.



    Initial dose: A single dose of up to 5mg/kg should be given on day 1.
    Maintenance dose: 1mg/kg to 4mg/kg once daily.
    Doses should be adjusted according to clinical requirements and haematological tolerance. This treatment should be maintained indefinitely, even if only low doses are necessary, as cessation of azathioprine therapy may result in graft rejection.

    Other conditions:
    Initial dose: 1mg/kg to 3mg/kg daily.
    Maintenance dose: May range from less than 1mg/kg to 3 mg/kg once daily.
    Adjust according to clinical response and haematological tolerance, the lowest effective dose should be maintained. Consider withdrawing treatment if no improvement within three to six months.

    The following alternative dosing schedule may be suitable:

    Severe acute Crohn's disease and maintenance of ulcerative colitis and Crohn's disease
    2mg/kg to 2.5mg/kg daily. Some patients may respond to lower doses.

    Treatment of severe refractory eczema (unlicensed)
    Normal or high TPMT (thiopurine methyltransferase) activity: 1mg/kg to 3mg/kg daily.
    Intermediate TPMT activity: 0.5mg/kg to 1.5mg/kg daily.


    The manufacturer suggests that the adult dose should be used in children (See Dosage; Adult).

    The following alternative dosing schedule may be suitable:

    Children aged 1 month to 18 years:1mg/kg to 3mg/kg once daily (as one single or two divided doses) titrated to response.

    Auto-immune conditions, systemic lupus erythematosus, vasculitis
    Children aged 1 month to 18 years: 1mg/kg daily titrated to a maximum of 3mg/kg daily if necessary. Consider discontinuation if there has been no improvement within three months.

    Severe Crohn's disease and ulcerative colitis
    Children aged 2 to 18 years old: 2mg/kg once daily, titrated to 2.5mg/kg once daily if necessary.

    Patients with Renal Impairment

    It is recommended that the dose should be at the lower end of the dosage range (See Dosage; Adult ).

    The Renal Drug Handbook suggests the following dose reduction:
    Glomerular filtration rate (GFR) greater than 20ml/minute: Dose as normal.
    GFR 10 to 20ml/minute: Reduce dose by up to 25%.
    GFR less than 10ml/minute: Reduce dose by up to 50%.

    Patients with Hepatic Impairment

    It is recommended that the dose should be at the lower end of the dosage range (See Dosage; Adult).


    None known

    Precautions and Warnings

    Inherited NUDT15 gene mutation
    Inherited thiopurine methyltransferase deficiency
    Recent exposure or co-existing varicella or herpes zoster
    Severe infection
    Glucose-galactose malabsorption syndrome
    Hepatic impairment
    Inflammatory bowel disease
    Lactose intolerance
    Lesch-Nyhan syndrome
    Renal impairment

    Administration of live vaccines is not recommended
    Consider prophylactic immunoglobulin if exposure to varicella virus
    Live virus vaccine should not be given for 3 months after treatment
    Not all formulations are licensed for all uses
    Passive immunisation of chicken pox / herpes zoster may be required
    Some formulations contain lactose
    Take at the same time in respect to food as absorption may be affected
    Monitor blood counts weekly for first 8 weeks and then monthly thereafter
    Monitor for signs of bone marrow depression
    Monitor for signs of Macrophage Activation Syndrome (MAS)
    Monitor hepatic function
    Advise patient to report symptoms of infection immediately
    Advise patient to report unexplained fever, sore throat, bruising, bleeding
    Immunosuppressive drugs may increase risk of malignancy
    May reduce effectiveness of vaccinations during treatment
    Potentially mutagenic and carcinogenic
    Reactivation of hepatitis B may occur in chronic carriers
    Reduce dose in patients with haematological toxicity
    Withdraw treatment gradually under supervision of a specialist
    Discontinue if Macrophage Activation Syndrome is suspected
    Discontinue if Progressive multifocal leukoencephalopathy (PML) develops
    Consider dose reduction in hepatic impairment
    Consider dose reduction in renal impairment
    Maintain treatment at the lowest effective dose
    Therapy should be maintained indefinitely in transplant patients
    Advise patient not to take with milk
    Dairy products may impair absorption
    Male & female: Ensure adequate contraception during treatment
    Advise patient to avoid exposure to sunlight and UV rays during treatment
    If exposed to chickenpox or Herpes zoster seek urgent medical attention

    It is suggested that during the first 8 weeks of therapy, complete blood counts, including platelets should be performed weekly (more frequently at higher doses and in severe renal and/or hepatic impairment). The blood count frequency may be reduced later in therapy, but it is suggested that complete blood counts are repeated monthly and at least every 3 months.

    There are individuals with an inherited deficiency of the enzyme thiopurine methyltransferase (TPMT) who may be unusually sensitive to the myelosuppressive effect of azathioprine and prone to developing rapid bone marrow depression following the initiation of treatment with azathioprine. This problem could be exacerbated by co-administration of drugs that inhibit TMPT, such as olsalazine, mesalazine and sulfasalazine.

    Limited evidence suggests that azathioprine is not beneficial to patients with Lesch-Nyhan syndrome (hypoxanthine-guanine phosphoribosyltransferase deficiency). Therefore given the abnormal metabolism in these patients it is not prudent to recommend that these patients should receive azathioprine.

    Relief of chronic renal insufficiency by renal transplantation involving the administration of azathioprine has been accompanied by increased fertility in both male and female transplant recipients.

    Pregnancy and Lactation


    Use azathioprine with caution in pregnancy.

    Does not appear to cause structural abnormalities when used during organogenesis.

    Exposure during the 3rd trimester has been linked to immunosuppression. Dose modifications appear to reduce the risk of toxicity.

    Briggs suggests that maternal treatment benefit outweighs potential risk to infant.

    There have been reports of premature birth and low birth weight following maternal exposure to azathioprine, particularly when in combination with corticosteroids. There have also been reports of spontaneous abortion following maternal and paternal exposure to azathioprine.

    Schaefer suggests a detailed ultrasound should be offered to confirm normal morphologic development in cases of first trimester exposure. If leucopenia occurs in the mother during the third trimester, dose should be reduced to avoid leucopenia in the neonate.

    The use of all medication in pregnancy should be avoided whenever possible; particularly in the first trimester. Non-drug treatments should also be considered. When essential, a medication with the best safety record over time should be chosen, employing the lowest effective dose for the shortest possible time. Polypharmacy should be avoided. Teratogens taken in the pre-embryonic period, often quoted as lasting until 14 to 17 days post-conception, are believed to have an all-or-nothing effect. Where drugs have a short half-life, and when the date of conception is certain, this may allow women to be reassured where drug exposure has occurred within this time frame. Further advice may be available from the UK National Teratology Information Service (NTIS) and through ToxBase, available via password on the internet ( ) or if this is unavailable at the backup site ( ).


    Use azathioprine with caution in breastfeeding

    6-mercaptopurine (a metabolite of azathioprine) has been identified in the colostrum and breast milk of women receiving azathioprine treatment.

    Some sources recommend avoiding breastfeeding for 2 to 6 hours after dose to further reduce the risk to infant.

    Studies of women taking azathioprine while breastfeeding have shown no adverse effects in nursing infants. However, long-term follow ups for effects have not been performed.

    Neonates, infants born prematurely, those with low birth weight, those with an unstable gastrointestinal function or who have serious illnesses may require special consideration. For any infant, if a drug is prescribed to the nursing mother, it should be at the lowest practical dose and for the shortest time. When drug administration is unavoidable and breastfeeding is to continue, minimisation of exposure of the infant to the drug may sometimes be achieved by timing the maternal doses to just after a feeding episode. Infants exposed to drugs via breast milk should be monitored for unusual signs or symptoms. Interactions between the drug received by the infant from the mother's milk and medication prescribed for the infant should also be considered, for example, when the drug given to the infant may prevent metabolism of the drug received via breast milk.
    Specialist advice is available from the UK Drugs in Lactation Advisory Service at


    May be taken with food or on an empty stomach. Administration with food may help relieve nausea however administration with food may reduce absorption. Patients are advised to standardise the method of administration.
    Advise patient not to take at least 1 hour before or 2 hours after milk or dairy products.
    Advise patient to report symptoms of bone marrow depression.
    Advise patient to report symptoms of infection immediately.
    Advise patient to avoid exposure to sunlight and UV rays during treatment, wear protective clothing and use sunscreen with a high protection factor.
    Advise patient to inform anaesthesiologist of their treatment with azathioprine prior to surgery.

    Side Effects

    Acute myeloid leukaemia
    Aplastic anaemia
    Bone marrow depression
    Bowel perforation
    Cholestatic jaundice
    Hepatic impairment
    Hypersensitivity reactions
    Increased risk of cervical cancer
    Increased risk of skin cancer
    Increased susceptibility to infection
    Interstitial nephritis
    Kaposi's Sarcoma
    Lymphoproliferative disorders
    Macrophage-activation syndrome
    Malignant melanoma
    Megaloblastic anaemia
    Myelodysplastic syndrome
    Nodular regenerative hyperplasia
    Non Hodgkin's lymphoma
    Non Kaposi's sarcoma
    Non melanoma skin cancer
    Peliosis hepatis
    Red cell hypoplasia
    Renal impairment
    Sinusoidal dilation
    Stevens-Johnson syndrome
    Toxic epidermal necrolysis
    Veno-occlusive disease


    It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.

    The following number will direct the caller to the relevant local centre (0844) 892 0111

    Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( ) or if this is unavailable at the backup site ( ).

    Further Information

    Last Full Review Date: September 2014

    Reference Sources

    Drugs During Pregnancy and Lactation: Treatment Options and Risk Assessment, 2nd edition (2007) ed. Schaefer, C., Peters, P. and Miller, R. Elsevier, London.

    Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk, 9th edition (2011) ed. Briggs, G., Freeman, R. and Yaffe, S. Lippincott Williams & Wilkins, Philadelphia.

    Martindale: The Complete Drug Reference, 36th edition (2009) ed. Sweetman, S. Pharmaceutical Press, London.

    The Renal Drug Handbook. 3rd edition. (2009) ed. Ashley, C and Currie, Radcliffe Publishing Ltd, Abingdon.

    Summary of Product Characteristics: Azapress 50mg tablets. Ennogen Pharma Ltd. Revised February 2012.

    Summary of Product Characteristics: Azathioprine 50mg tablets. Actavis UK Ltd. Revised January 2014.
    Summary of Product Characteristics: Azathioprine 50mg tablets. Arrow generics Ltd. Revised March 2012.
    Summary of Product Characteristics: Azathioprine 50mg Tablets. Co-pharma Ltd. Revised January 2010.

    Summary of Product Characteristics: Azathioprine 25mg tablets. Generics UK. Revised November 2013.
    Summary of Product Characteristics: Azathioprine 50mg tablets. Generics UK. Revised November 2013.

    Summary of Product Characteristics: Azathioprine 25mg tablets. Norton healthcare Ltd. Revised January 2013.
    Summary of Product Characteristics: Azathioprine 50mg tablets. Norton healthcare Ltd. Revised January 2013.

    Summary of Product Characteristics: Azathioprine 25mg tablets. Sandoz Ltd. Revised May 2013.
    Summary of Product Characteristics: Azathioprine 50mg tablets. Sandoz Ltd. Revised March 2014.

    Summary of Product Characteristics: Azathioprine 25mg tablets. Tillomed Ltd. Revised October 2012.
    Summary of Product Characteristics: Azathioprine 50mg tablets. Tillomed Ltd. Revised October 2012.

    Summary of Product Characteristics: Imuran 25mg Tablets. Aspen Europe. Revised October 2019.
    Summary of Product Characteristics: Imuran 50mg Tablets. Aspen Europe. Revised October 2019.

    NICE Evidence Services Available at: Last accessed: 21 June 2017

    UK Drugs in Lactation Advisory Service.
    Available at:
    Last accessed: 12 September, 2014.

    US National Library of Medicine. Toxicology Data Network. Drugs and Lactation Database (LactMed).
    Available at:
    Azathioprine Last revised: 8 July 2014
    Last accessed: 12 September 2014.

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