Gastroenterology: Medications

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All About Imuran (azothioprine)

Many patients are not as well informed about prescription medications as they ought to be. We believe the more you know about your medications, the better. This article has been written to help you understand more about what Imuran is and the importance of taking it properly. If any of the information causes you special concern or if you want additional information about your medicine and its use, check with your doctor or pharmacist.

If any of the information in this leaflet causes you special concern or if you want additional information about your medicine and its use, check with your doctor or pharmacist.

Remember to keep all prescription drugs out of reach and sight of children when not in use. Store Imuran in the original labeled container in a cool dry place. Protect from light. Always read the label before using.

What is Imuran?

Introduced in 1968, Imuran is a powerful drug that weakens the immune system. It is often used to prevent rejection of kidney transplants. It is also used to treat severe cases of rheumatoid arthritis, systemic lupus, polymyositis, Crohn's disease, ulcerative colitis, and other "autoimmune" disorders. Its use is usually confined to patients who have failed to respond adequately to simpler treatment.

The generic name of Imuran is azothioprine (ay za THYE oh preen). Each tablet contains 50 milligrams and is easily broken in half when dosage adjustments are needed. Imuran, itself, does not act against IBD. After being absorbed by the intestines, it is changed in the liver to a chemical called 6-mercaptopurine, or 6-MP. This form of the drug is also available by prescription and sold as Purinethol.

What Imuran is not.

Imuran is not the same as the prednisone. But, Imuran depresses the immune system as does prednisone. This usually allows your doctor to reduce your dose of prednisone resulting in less side effects.

Imuran is not habit-forming. It does not cause drowsiness and will not affect your driving or working. It does not cause sexual impotence. There are no restrictions on exposure to sunlight.

How does Imuran work?

Immunomodulating agents, or drugs that suppress the immune system, such as Imuran have become important tools in the long term treatment of inflammatory bowel diseases such as Crohn's disease and ulcerative colitis. Although the exact mechanism of how Imuran works is not known, it is felt that by inhibiting the immune system, this drug suppresses the "overactive" immune reaction that is responsible for such disorders as Crohn's disease and Ulcerative Colitis.

Taking Imuran properly

    1. Imuran is best taken with food. Imuran can irritate the stomach lining and therefore should be taken with food which serves as a buffer and reduces the irritation. The tablets may be crushed if necessary. There are no food or beverage restrictions. Imuran can be taken with milk. It does not interact with alcohol or tobacco.

    2. Take the dose as prescribed once daily. There is no fixed rule for the correct dose of Imuran. The average dose is one or two tablets daily, but each case is different. Your doctor will determine what initial dose is best for you depending on the activity of your disease, your age, weight, any other medical conditions you may have, and your response to treatment - do not alter the dose on your own. The goal, of course, is to control your illness with the lowest effective dose of Imuran possible. Your doctor will routinely reassess what dose is necessary for you. The tablets may be crushed if necessary. If two tablets are prescribed, they may be taken at the same time once daily.

    3. If you forget a dose, take the normal dose of the medication as soon as you remember and resume your normal schedule the following morning. If you do not remember until the next day, skip the missed dose.

    4. Do not expect immediate results. Imuran does not work right away. In fact, it may take more than 3 months to show a beneficial response. You can plan to be on this drug anywhere from 3 months to several years.

    5. Keep all your appointments. Imuran is only given under close supervision because of the risk of serious adverse effects. Periodic blood tests are mandatory for the safe use of this drug. Report for examinations as directed.

    6. Be sure all of your doctors know that you are taking this drug. This is a good general rule, but it is especially important for you to remember if you are away from your doctor and require major surgery or develop a severe infection. If you are to be on Imuran for a long period of time, carry a reminder with you on a Medic-Alert bracelet or in your wallet. (Medic-Alert Foundation can be contacted at their toll-free number 800-344-3226)


What are the side effects?

This is the main concern. When taken over a long period of time (months to years) Imuran can cause many side effects. But when Crohn's disease or ulcerative colitis become difficult to control with prednisone, the benefit of Imuran far outweighs the potential risks. For difficult to manage conditions, Imuran can be a miraculous medication. In general, the risk of side effects depends on the length of time you take Imuran and the amount you take.

These side effects can occur with short term use but fortunately are usually reversible as the dose of Imuran is decreased:

  • skin rash
  • loss of appetite
  • nausea, vomiting
  • diarrhea
These side effects are more serious. They usually occur after long term usage. Immediately report any of these symptoms to your doctor:
  • Bone marrow depression
    • severe fatigue
    • weakness
    • fever
    • severe sore throat
    • abnormal bleeding or bruising
    • sores on lips and in mouth
  • Liver damage
    • yellow eyes and skin
    • jaundice
    • dark-colored urine
  • Drug-induced pneumonia
    • severe persistent cough
    • shortness of breath
  • Pancreatitis
    • severe stomach pain
    • nausea and vomiting
Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor, nurse, or pharmacist.

You can help limit side effects by taking the medication exactly as prescribed and reporting any problems to your doctor. Report promptly any indication of a developing infection - fever, chills, lip or mouth sores, etc.

What about cancer?

Some doctors feel that there may be a slightly increased risk of some cancers such as lymphoma or Hodgkins disease after long-term use of Imuran. But , a scientific study done at the University of Pennsylvania in 2001 studied 1467 patients with Ulcerative colitis or Crohn's Disease and found no increased risk of lymphoma in patients who took Imuran. However, there is still some controversy about this point - so you must be willing to accept this possible risk if you take Imuran. Again, this powerful drug is only used as a last resort in patients with severe inflammatory bowel disease who do not respond to conventional treatment. In general, it is felt that the benefits of Imuran in this difficult situation outweigh the risks.

Monitoring Imuran

Each patient is different and the optimum dose of Imuran varies from one individual to another. There is sometimes a narrow range between the most effective dose and a toxic dose. The doctor determines the best dose based on age, weight, response to treatment, and monitors symptoms and blood tests for side effects.

Technology is also now available that allows for more accurate dose adjustment. The metabolites of Imuran called 6-TG and 6-MMP can be directly measured in the blood. Higher 6-TG levels correlate with clinical response to Imuran but also the risk of bone marrow suppression. Higher 6-MMP levels correlates with liver toxicity. These special blood tests may be requested from Prometheus Laboratories to help the doctor determine the proper dose. Studies at the Cleveland Clinic have suggested that 6-TG levels greater than 260 are necessary for a clinical benefit and 6-MMP levels over 5700 have been associated with liver toxicity.


Do not take Imuran if you are pregnant or plan to become pregnant in the near future. Birth defects have been reported in animals that received large doses of Imuran during pregnancy. This drug also has the potential for producing birth defects in human offspring. Use of this drug is not recommended during pregnancy. There is a possibility that birth defects may occur if either the mother or father is using Imuran at the time of conception. Use of birth control is recommended while taking this drug. Do not breast feed while on this drug.

Notify your doctor if you recently had chickenpox or shingles. Be sure to inform him if you are taking allopurinol (Zyloprim), Dilantin, Rifampin, or phenobarbital. These drugs may increase the blood levels of Imuran, which can lead to serious side effects. Tell your doctor if you have any kind of active infection, have a history of bone marrow disorders, severe liver or kidney disease, or are pregnant or plan to become pregnant in the near future. Be aware that Imuran can lessen the effects of the anticoagulant drug Coumadin.


Imuran is a very powerful drug with many helpful properties, but as with all potent medications, side effects may occur. You can best limit problems with this medication by taking it exactly as prescribed. If you have any questions or concerns, please discuss them with your doctor.

Text & Images Courtesy of Three Rivers Endoscopy Center
© Dr. Robert Fusco, Three Rivers Endoscopy Center, All Rights Reserved

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