Azathioprine (Imuran)


Background

Azathioprine is one of the common medications used alone or in combination for immune-mediated diseases. In patients treated with azathioprine, prednisone therapy can be decreased and possibly even discontinued.

Azathioprine disrupts the synthesis of DNA and RNA. In the treatment of immune mediated diseases, it is the stimulated lymphocytes that are inappropriately attacking the body that become the prime target of azathioprine.
Because azathioprine can disrupt rapid cell division, its use also has application in treating cancers.

Some typical immune mediated conditions that commonly require the use of azathioprine include immune-mediated hemolytic anemia (IMHA), immune-mediated platelet destruction (thrombocytopenia), pemphigus-type skin diseases, severe forms of inflammatory bowel disease (IBD), immune-mediated arthritis, etc.

Side Effects

  • One of the main issues with azathioprine is a problem with the bone marrow suppression. Cells of the bone marrow are rapidly dividing and thus at risk for suppression from azathioprine. For this reason, at least in early stages of use, complete blood counts (CBC) are monitored frequently (typically every 2 weeks for the first couple of months).
  • Signs of a bone marrow problem that might be observable at home include abnormal bruising or inappropriate bleeding (bloody nose, bloody stool, blood in urine, excess bleeding from a minor wound, etc.)
  • Some patients develop a liver toxicity or pancreatitis with azathioprine. This should resolve with discontinuation of the medication. It is important to watch for signs of nausea, diarrhea, or appetite loss during the first few weeks of therapy.

Interactions with other Drugs

As it can take a good month or two before the benefits of azathioprine are seen, it is a good idea to begin azathioprine in conjunction with a stronger immuno-suppressive agent such as prednisone that will rapidly control the disease.

Cautions and Concerns

  • Azathioprine should not be used in pregnant pets nor should pregnant owners handle it.
  • Azathioprine should not be used in patients with pre-existing liver disease if possible.

Veterinarian’s Comment

  • Azathioprine tablets should be protected from light exposure and kept in coloured plastic medication vials and stored in a drawer or cabinet if possible.
  • It is a good idea to wash your hands after handling azathioprine tablets.