Imuran (Azathioprine)

Immunosuppressive drug, Purine antagonist, Autoimmune disease, Bone marrow suppressant

Brand Names


Drug Information


Purine antagonist antimetabolite-immunosuppressive drug.

Less immunosuppressive with less side effects than cyclophosphamide.


  • Contraindicated in patients with known sensitivity to this type of drug.
  • Use with caution in cases with pre existing liver disease.
  • Use with caution if at all in patients with pre existing bone marrow suppression.
  • Contraindicated in pregnancy due to risk of teratogenicity.
  • Generally contraindicated in cats due to the potential for causing bone marrow suppression.

Adverse Effects

  • Acute hepatotoxicity, jaundice, GI upset, skin eruptions, poor hair growth and pancreatitis have also been reported.
  • Animals are more susceptible to infection while on this drug.
  • Doses should be slowly tapered once resolution of hemolytic anemia is achieved to minimize the risk for rebound hyperimmune response.
  • Bone marrow suppression-usually leukopenia but also thrombocytopenia and anemia.
  • Bone marrow suppression-usually leukopenia but also thrombocytopenia and anemia. Cats are more prone to this side effect and therefore it is not recommended in this species.


General Interactions
  • Astragalus may impair the immunosuppressive effects of AzaTHIOprine.

Category Interactions
Non-depolarizing neuromuscular blocker
  • Neuromuscular blocking activity may be inhibited or reversed.

Drug Interactions
  • Allopurinol inhibits the hepatic metabolism of AzaTHIOprine. Reduced dosages are needed.
  • Toxic levels of AzaTHIOprine can result if used concurrently.
  • Additive risk for bone marrow suppression – use together is not advised in humans.
Pancuronium bromide
  • AzaTHIOprine may reverse effects.
Vecuronium bromide
  • AzaTHIOprine may reverse effects.


After reconstitution with sterile water for injection, use within 24 hours as it contains no preservatives.
Monitor hemogram and platelets every 1 – 2 weeks initially and every 1 – 2 months once on maintenance therapy.
If WBC drops to 5000 – 7000 cells/mm3 the dose should be reduced or if < 5000 discontinued until leukopenia resolves.
Monitor liver function tests periodically and efficacy.
May take 4 – 6 weeks to see response.
Often used with corticosteroids.
For specific information regarding protocols, see specialized reference material.

Available Forms

  • Tablets- 50 mg; Imuran ® Injection- 100 mg per vial in 20 mL vial, Imuran® and generic.
Veterinary – General
  • None