Azathioprine (Imuran)
Purine antimetabolite prodrug nonenzymatically cleaved to 6-mercaptopurine (6-MP), which is further metabolized to active thioguanine nucleotides (6-TGN) incorporated into DNA/RNA to inhibit lymphocyte proliferation. Used for IBD (steroid-sparing in Crohn's/UC), autoimmune hepatitis, lupus, solid-organ transplant, and dermatologic autoimmune disease. Typical dose 1-3 mg/kg/day PO (50-200 mg/day). Parent t1/2 ~5h; 6-MP t1/2 ~2h but active 6-TGN red-cell levels accumulate over weeks. F~47%. TPMT and NUDT15 genotyping recommended before initiation, deficient metabolizers develop life-threatening myelosuppression at standard doses. Avoid co-administration with allopurinol/febuxostat (xanthine oxidase inhibition leads to toxic 6-MP accumulation), requires 75% dose reduction.
Projected serum levels — 100 mg, once daily
Maintenance schedule: 100 mg once daily (oral).
Modeled steady state after ~1 days: peak ≈ 9.9 mg, trough ≈ 0.000 mg body load. Population-based estimate over 15 days for a 100 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.
Key facts
- Category
- Immunosuppressant
- Route modeled
- Oral
- Model confidence
- inferred
- Half-life
- 1.5 h
- Common dose
- 100 mg
- Suggested maximum
- 250 mg/day
- Reference dose range
- 50–250 mg (single dose)
- Suggested cadence
- once daily
- Validated against
- 100 mg oral — Cmax 0.10 mg/L at 2 h
Documented interactions
-
moderate
6-Mercaptopurine + Azathioprine (Imuran)
6-Mercaptopurine and Azathioprine (Imuran) both push the dna purine incorporation and tpmt in the same direction.
-
moderate
Allopurinol + Azathioprine (Imuran)
Allopurinol mechanism_based of xanthine_oxidase predicted to change Azathioprine (Imuran) AUC by ~1.68x
Serum checks 2 modeled interaction pairings for azathioprine (imuran) across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.
Research behind this entry
-
Clinical pharmacokinetics and pharmacodynamics of mercaptopurine
Foundational PK work on 6-MP (azathioprine's active metabolite): oral bioavailability ~16-50%, interpatient variability largely explained by TPMT activity and first-pass metabolism.
-
Thiopurine methyltransferase (TPMT) genotype and early treatment response to mercaptopurine in childhood acute lymphoblastic leukemia
Landmark study linking TPMT deficiency genotypes to severe myelosuppression with thiopurines - established the rationale for pre-treatment TPMT genotyping now standard of care.
2 published studies referenced in the app, each with a plain-language summary.