Azathioprine

« Back to Glossary Index

Azathioprine (brand name Imuran or Imurel) is an immuno-suppressant drug used for the treatment of  auto-immune conditions such as AIHA, some types of cancer and as an anti-rejection drug for human organ transplant recipients.  Azathioprine can take up to 6 weeks longer  than prednisone to suppress the immune system’s cellular immunity. Azathioprine takes about 10 days to suppress the T-lymphocytes which can attack the body’s own cells by mistake, so a response to treatment may not be seen immediately.

Azathioprine should be given WITH FOOD, 2 hours before or 2 hours after stomach protectors, which can stop proper absorption of the drug.

Dose is usually 1 mg/lb/day for 7-10 days , then taper down over several weeks.  In the long term, Azathioprine may only be required every other day or even less often.

Possible side effects can include pancreatitis, bone marrow suppression, liver toxicity & increased susceptibility to infections. Careful observation is needed for symptoms of pancreatitis or liver toxicity, such as abdominal pain or discomfort, vomiting and/or diarrhea.

If you suspect your pet has any of these symptoms, call your vet and ask if you can discontinue the azathioprine immediately. Visit a veterinary surgery or hospital for further advice on treatment of the symptoms as soon as possible.

Azathioprine has serious & extreme interactions with some other drugs & moderate/mild interactions with others. Interactions with other drugs include allopurinol, ACE inhibitors, (e.g. enalapril), other immuno-suppressants such as MMF, cyclosporine, cyclophosphamide, chlorambucil, drugs that affect the bone marrow, some anticoagulents (e.g. heparin, warfarin, enoxaparin) & alkylating chemotherapy drugs, plus other chemotherapy drugs, also aminosalicylates. Please remember some interactions are mild, but others may be more serious. Be sure to  ask you vet about this. It is very important to tell your vet if your pet is being given any other medicines, drugs or supplements.

Modified live vaccines must NOT be given during treatment with azathioprine as severe interactions have been reported in humans & animals.

Azathioprine may also react with some vitamins & supplements – always ask your vet for advice.

Azathioprine must NEVER be given to animals being used for breeding as it can alter DNA transcription in fast growth cells. With long-term use, there are increased risks for neoplasms. Careful weaning to reduce the dosage is advisable when the dog has reached a stable condition.

« Back to Glossary Index