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Thiopurine Immunosuppressant

Azathioprine 1–3mg/kg/day

Brand names: Imuran, Azapress

Azathioprine is a thiopurine immunosuppressant used in renal practice for maintenance immunosuppression in transplantation and as a steroid-sparing agent in lupus nephritis and other glomerular disease.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

Clinical monograph

How it works

It is metabolised to mercaptopurine and active thioguanine nucleotides that inhibit purine synthesis, suppressing proliferation of lymphocytes and dampening the immune response.

Prescribing in practice

  • Profound myelosuppression can occur, particularly in those with reduced TPMT activity, so check TPMT before starting and monitor the full blood count.
  • Never co-prescribe with allopurinol or febuxostat without a major dose reduction, as xanthine oxidase inhibition causes dangerous thiopurine accumulation.
  • Counsel on increased long-term risk of infection and of skin and other malignancies, and advise sun protection.

Monitoring

Monitor full blood count regularly (more frequently after initiation or dose change) together with liver function.

Counselling the patient

  • Attend for your blood tests as scheduled, as they detect effects on the bone marrow.
  • Report sore throat, fever, bruising or unusual bleeding promptly.
  • Use sun protection and report any new or changing skin lesions.

Evidence & guidelines

Pre-treatment TPMT testing and routine blood-count monitoring for azathioprine are supported by MHRA advice and specialist renal guidance.

Reference: KDIGO Transplant Guidelines 2009; UK Renal Association; MHRA Drug Safety Update (azathioprine-allopurinol interaction); Confirm identity and dosing against the manufacturer SPC (eMC) and NICE. Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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