Description
Azathioprine
(Imuran) is an anti-inflammatory medication that is considered an immunosuppressant or disease-modifying antirheumatic drug (DMARD). This category of medicines can decrease joint damage and disability.
Uses
Azathioprine is used to treat many inflammatory conditions, such as rheumatoid
arthritis, systemic lupus
erythematosus (lupus), inflammatory myositis, vasculitis and inflammatory
bowel disease. It is also used to prevent transplant rejection.
How it works
Azathioprine works by suppressing immune system activity. Although the immune
system is important for fighting infections, immune system cells sometimes
mistakenly attack the body's own tissues. Azathioprine counters this by
interfering with deoxyribonucleic acid (DNA) synthesis, which prevents cells
(including those in the immune system) from dividing.
Dosing
Dosage of this medication depends on the disease being treated. The initial dose for rheumatoid arthritis is approximately 1 milligram/kilogram (mg/kg) of body weight, or approximately 50 to 100 mg given as a single dose or twice daily. This can be increased every 1 to 2 months, up to a maximum dose of 2.5mg/kg of body weight, or approximately 75 to 150 mg given twice a day.
Time to effect
Improvement in arthritis and other conditions may appear in 6 to 8 weeks, although it may take up to 12 weeks to notice maximum benefits.
Side Effects
The most common and potentially serious side effects of azathioprine involve the gastrointestinal tract and blood cells. Approximately 10 to 15 percent of patients experience nausea and vomiting after taking this medication, sometimes accompanied by abdominal pain or diarrhea. Taking the medication twice daily instead of all at once, or taking it after eating, may help avoid these problems.
Less often, azathioprine has been associated with liver test abnormalities, hepatitis (inflammation of the liver), pancreatitis (inflammation of the pancreas gland behind the stomach that can cause abdominal pain) or an allergic reaction that may include a flu-like syndrome. Azathioprine also can lower infection-fighting white blood cells.
During treatment, your doctor may test for the breakdown products (metabolites) of azathioprine which can help monitor for toxicity and increase efficacy.
Long-term use of azathioprine in combination with other immune suppressing medications in transplant patients has been associated with a slightly elevated risk of cancer. It is not clear whether arthritis patients face a similar risk.
Points to remember
It is important to take azathioprine as directed, have regular blood tests and notify your doctor if you notice the following while taking this medication: fever, rash, easy bruising or bleeding, or signs of an infection. Be sure to talk with your doctor before receiving any vaccines or undergoing any surgeries while taking this medication.
If you are pregnant or are considering having a child, discuss this with your doctor before beginning this medication. Use of an effective form of birth control is important throughout the course of this treatment and for months after it is stopped. Breast-feeding while taking azathioprine is not recommended because azathioprine is excreted into the breast milk.
Drug Interactions
Be sure to tell your doctor about all of the medications you are taking,
including over the counter drugs and natural remedies. Medications that
may interfere with azathioprine include the gout medication allopurinol
(
Aloprim; Zyloprim), warfarin (
Coumadin),
some blood pressure medications including some ACE inhibitors (
Accupril or
Vasotec),
olsalazine
(
Dipentum), mesalamine (
Asacol, Pentasa), and
sulfasalazine (
Azulfidine).
For more information
The American College of Rheumatology has compiled this list to give you
a starting point for your own additional research. The ACR does not endorse
or maintain these Web sites, and is not responsible for any information
or claims provided on them. It is always best to talk with your rheumatologist
for more information and before making any decisions about your care.
National Institutes of Health
http://www.nlm.nih.gov/medlineplus/druginfo/uspdi/202077.html
Updated June 2006
Written by Michael Cannon, MD, and reviewed by the American College of
Rheumatology Patient Education Task Force.
