azathioprine: prescribing and clinical use
Focused clinical detail for use alongside current product information, local policy and patient-specific assessment.
azathioprine: clinical details
Prescribing considerations
- Initiation and ongoing supervision should be by clinicians experienced in immunosuppression, with capacity for continuing toxicity monitoring.
- Assess infection and vaccination status, renal and hepatic function, blood count and TPMT activity before treatment; consider NUDT15 susceptibility where clinically relevant.
- Review concomitant medicines, particularly xanthine-oxidase inhibitors, ribavirin, myelosuppressants, aminosalicylates and anticoagulants.
- Counsel about infection, chickenpox or shingles exposure, sun protection and the long-term increased risk of skin and lymphoproliferative malignancy.
Contraindications and cautions
- Hypersensitivity to azathioprine, mercaptopurine or relevant excipients.
- Jayempi specifically contraindicates live vaccines and breastfeeding; these restrictions must not automatically be assumed to describe every tablet licence.
- Use only after careful benefit–risk assessment in severe active infection, major liver or bone-marrow dysfunction, pancreatitis, renal impairment or known thiopurine-metabolism deficiency.
Monitoring
- Monitor full blood count, liver function and renal function throughout treatment, with greater vigilance after initiation, treatment changes or in people at increased toxicity risk.
- Review trends as well as absolute values; falling white cells, neutrophils, platelets or albumin and rising liver enzymes may indicate toxicity.
- Consider periodic skin examination and advise prompt assessment of infection, bleeding, bruising, jaundice or severe systemic illness.
Clinical pharmacology
Azathioprine is a prodrug of mercaptopurine. Intracellular conversion produces thiopurine nucleotides that interfere with purine metabolism and immune-cell proliferation; metabolism varies substantially between individuals and is affected by TPMT, NUDT15 and xanthine oxidase activity.
Formulation and product differences
- The selected tablet contains lactose and is intended to be swallowed whole; administration should be consistent in relation to food and separated from dairy products.
- Jayempi is an oral suspension that must be shaken before measurement with the supplied syringe and followed with water. It contains sodium benzoate and has cytotoxic-handling precautions.
- Jayempi has a limited in-use shelf life after opening and may be preferable when a solid formulation cannot be swallowed.
- Contraindication wording differs between the selected products, particularly for live vaccines and breastfeeding.
azathioprine preparations and strengths
Oral suspension
Route: Oral
Strengths: 10 mg/mL
Tablet
Route: Oral
Strengths: 25 mg, 50 mg
azathioprine interactions
Check all prescribed, over-the-counter and complementary products with a pharmacist or prescriber.
Allopurinol, oxipurinol or thiopurinol
These strongly reduce azathioprine breakdown, creating a potentially severe toxicity risk requiring specialist adjustment and close monitoring.
Febuxostat
It may substantially increase azathioprine exposure and bone-marrow toxicity; combined use is not recommended in the selected product information.
Ribavirin
It can reduce azathioprine efficacy while increasing severe bone-marrow toxicity, so combined use is not advised.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.