BRAND NAME: IMURAN
AVAILABLE IN
50 mg
TABLETS
BACKGROUND
Diseases involving excessive activity of the immune system are called
“immune mediated” diseases and they are treated with suppression
of the immune system. The cornerstone medication of immune suppression
is prednisone; however, this medication may have undesirable side
effects with long term use, thus it is helpful to look towards a
second medication that can be used to reduce the prednisone amount
used. Azathioprine is such a medication, though it is important to
realize that it can have some of its own adverse side effects in
some individuals. In patients who do not have any problems with azathioprine
(and most do not), prednisone can be reduced and possibly even discontinued.
Azathioprine disrupts the synthesis of DNA and RNA. This means that
it disrupts cell division and that tissues with relatively rapid
cell division are especially prone to its effects. 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.
Because Azathioprine is a DNA poison it has the potential to cause
mutation.
HOW THIS MEDICATION IS USED
Some typical immune mediated conditions that commonly require the
use of azathioprine include:
Immune mediated hemolytic anemia
Immune mediated platelet destruction (thrombocytopenia)
Pemphigus type skin diseases (especially pemphigus foliaceus)
Severe forms of inflammatory bowel disease
Chronic Active Hepatitis (a progressive scarring disease of the
liver)
Myasthenia Gravis (immune mediated destruction of the nerve/muscle
junctions)
Systemic Lupus Erythematosus
Rheumatoid/immune mediated arthritis
Azathioprine is typically started once a day and then tapered to
every other day use and is almost always started in conjunction
with other immune suppressive agents.
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’s”)
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.) If bone marrow suppression has not occurred in the first couple
of months of therapy, it is unlikely that it will occur later on.
Some patients develop a liver toxicity with azathioprine. This should
resolve with discontinuation of the medication but it is important
to watch for any signs of nausea, diarrhea, or appetite loss. If
these occur, especially in the first few weeks of starting azathioprine,
discontinue the medication and notify your veterinarian of these
effects.
Similarly, azathioprine can promote pancreatitis. Again, signs of
nausea/intestinal upset can result. If this occurs, discontinue azathioprine
and notify your veterinarian.
INTERACTIONS WITH OTHER DRUGS
Because 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 an aggressive prednisone course. The prednisone will hopefully
control the disease rapidly such that by the time the azathioprine
has “kicked in,” the prednisone can be tapered to a maintenance level.
Concurrent use of allopurinol can present a problem with azathioprine
use. This normally would only come up in the event of a Dalmatian
using allopurinol to control uric acid bladder stone issues. If azathioprine
is to be used with allopurinol, the dose of azathioprine must be
dramatically reduced.
CONCERNS AND CAUTIONS
Azathioprine tablets should be protected from light exposure. They
should be kept in a colored plastic medication vial and stored in
a drawer or cabinet if possible.
Azathioprine should not be used in pregnant pets nor should it
be handled by pregnant owners.
Azathioprine should not be used in patients with pre-existing liver
disease if possible. (It should be noted that most patients starting
azathioprine have been on prednisone or other steroids and will
have elevations in liver enzymes as a result of steroid exposure.
This is not the same as having pre-existing liver disease and does
not represent a problem.)
Many experts feel that azathioprine should not be used in the cat
at all, due to extra sensitivity of the bone marrow in this species.
If azathioprine is to be discontinued after long term use, it is
probably best to taper the dosage rather than discontinue abruptly
as a rebound increase immune response can result.
It is a good idea to wash your hands after handling azathioprine
tablets
Azathioprine Medical Center Azathioprine
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