First-lineImuran
Azathioprine
Purine antimetabolite
IBD / SLE / transplant — compatible in pregnancy.
Oral
First-line for
- IBD maintenance in pregnancy
- SLE / vasculitis maintenance
- Post-transplant immunosuppression
Mechanism
Prodrug → 6-MP → inhibits purine synthesis → ↓ lymphocyte proliferation.
AZA pregnancy
- Continue (placenta lacks inosinate pyrophosphorylase)
- Check TPMT before starting
Dosing
- Maintenance
- 1–2.5 mg/kg/day PO
Contraindications
- AbsoluteTPMT deficiency (severe myelosuppression)
Side effects
- Marrow suppression
- Hepatotoxicity
- ↑ skin malignancy risk long-term
Fetal & maternal notes
- • Compatible pregnancy & breastfeeding (transfer minimal).
- • Continue to avoid disease flare.
Key interactions
Allopurinol
AvoidMassive ↑ AZA toxicity — reduce dose 75%
ACEi
CautionAnaemia
Clinical pearls
- 💡 FBC monitoring weekly initially.
- 💡 Mycophenolate must be swapped pre-conception.
Content last reviewed: REPLACE_ME (e.g. 2026-07)
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