Medications and Drugs
Pharmacy Author: Annette O. Gbemudu, PharmD, MBA
Medical and Pharmacy Editor: Jay W. Marks, MD
GENERIC NAME: azathioprine
BRAND NAME: Imuran, Azasan
DRUG CLASS AND MECHANISM: Azathioprine is an immunosuppressant, that is, a drug that is
used to suppress the immune system. It is used to treat patients who have
undergone kidney transplantation and for diseases in which activity of the
immune system is important. Azathioprine is a prodrug (a precursor of a drug)
which is converted in the body to its active form called mercaptopurine
(Purinethol). The exact mechanism of action of azathioprine is not known.
Like
other immunosuppressants, it suppresses the proliferation of T and B
lymphocytes, types of white blood cells that are part of the immune system and
defend the body against both infectious diseases and foreign materials. For
example, in the case of organ transplantation, immunosuppressants prevent the
body from immunologically rejecting the new organ. In the case of autoimmune
diseases (diseases caused by an abnormal immune reaction against the body's own
tissues) such as rheumatoid arthritis, suppressing the immune system reduces the
inflammation that accompanies immune reactions and slows damage to the joints
caused by the inflammation.
PRESCRIPTION: Yes
GENERIC AVAILABLE: Yes
PREPARATIONS: Tablet: 50, 75, 100 mg. Injection: 100 mg
STORAGE: Azathioprine should be stored at 15-25 C (59-77 F) in a dry
place and protected from light.
PRESCRIBED FOR: Azathioprine is used for preventing rejection of transplanted
kidneys. Azathioprine also is used for the treatment of severe, active,
rheumatoid arthritis in patients who do not respond to rest,
aspirin, or other
nonsteroidal antiinflammatory drugs.
Non-FDA approved uses for azathioprine
include multiple sclerosis, where several clinical trials have shown decreases
in relapses but no slowing in progression of the disease. There also is limited
data on the safety of azathioprine in multiple sclerosis. Other non-FDA
(off-label) uses of azathioprine include Crohn's disease, myasthenia gravis,
chronic ulcerative colitis, and autoimmune hepatitis (in combination with
prednisone).
DOSING: Azathioprine should be taken with food.
DRUG INTERACTIONS: Allopurinol (Zyloprim) that is used for treating increased
blood levels of uric acid and preventing gout increases azathioprine levels in
the blood which may increase the risk of side effects from azathioprine.
Therefore, it is important to reduce the dose of azathioprine by approximately
1/3 to 1/4 in patients taking allopurinol. The use of
angiotensin-converting
enzyme (ACE) inhibitors to control high blood pressure in patients taking
azathioprine has been reported to induce anemia (low levels of red blood cells)
and severe leukopenia (low levels of white blood cells). Azathioprine reduces
blood levels of the blood thinner, warfarin (Coumadin), and thus may reduce the
blood thinning effect of warfarin. Safety and efficacy of azathioprine in
children have not been established
PREGNANCY: Azathioprine can cause fetal harm when given to
pregnant women and
whenever possible should be avoided.
NURSING MOTHERS: Azathioprine is found in
breast milk and should not be used
in nursing mothers.
SIDE EFFECTS: The most common serious side effects of azathioprine involve
the cells of the blood and gastrointestinal system. Azathioprine can cause
serious lowering of the white blood cell count, resulting in an increased risk
of infections. This effect is reversed when the dose of azathioprine is reduced
or temporarily discontinued. Azathioprine can cause nausea,
vomiting, and loss
of appetite, which may resolve when the daily dose is reduced or divided and
taken more than once a day. Azathioprine can cause liver toxicity (for example,
in less than 1% of rheumatoid arthritis patients). All patients taking
azathioprine require regular testing of blood for blood cell counts and liver
tests to monitor for side effects of azathioprine. Other side effects
encountered less frequently include fatigue, hair loss, joint pains, and
diarrhea.
Reference: FDA Prescribing Information
Last Editorial Review: 2/17/2009
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
- Drug Interactions - Learn about potential drug interactions you may be exposed to. Drug interactions can occur with prescription drugs, OTC medication, vitamins, herbs, and supplements.
- Rheumatoid Arthritis - Learn more about rheumatoid arthritis, an autoimmune disease that causes chronic joint inflammation, which has symptoms that include stiffness, fever, muscle and joint aches, loss of appetite, and fatigue. Treatment of rheumatoid arthritis incorporates the use of first-line drugs (aspirin and corticosteroids for pain and inflammation) and second-line drugs (methotrexate and hydroxychloroquine to prevent joint destruction and promote remission).
- Drugs: What You Should Know About Your Drugs - Find out what you should know about your drugs such as side effects, warnings and precautions, storage information, and if a generic version is as good as the brand name.
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