What is it?

6-MP (6-Mercaptopurine) and Imuran (Azathioprine) are under the class of medications called immunosuppressants. They work by suppressing a part of the immune system that is overacting and responsible for the inflammation in the body.

Why do I need this medication?

These medications are used to treat ulcerative colitis or Crohn’s Disease and are effective in helping individuals stop and avoid the need for steroids.

How long do I have to take this medication?

6-MP and Imuran are used to induce remission (make you feel better) and are also effective maintenance drugs that will reduce the chances of a flare. This requires the medication to be taken on a regular basis.

How do I take it?

This medication comes in pill form and is taken once daily. There are 2 ways to start on therapy:

  • Full Dose Start: 1 in 300 people do not have the enzyme needed to break down this medication in the body. A special blood test can be done to measure that particular enzyme activity. This test is done at St. Paul’s Hospital on Mondays, Tuesdays, and Wednesdays, and will cost $50. The results usually take 2-3 weeks. If this test is done, you can start on the full dose of 6-MP or Imuran at the start of therapy.
  • Low Dose Start: If the blood test is not done, it is necessary to start at a lower dose of the medication for 2 weeks. Start with 1 pill per day. After 2 weeks, you may increase your dose to the full amount. Please call the office prior to increasing your dose.

When will I start to feel better?

6-MP and Imuran take approximately 2-3 months before you can see the full benefits of their effects.

What happens when I want to get pregnant?

These medications are relatively safe during pregnancy but family planning should be discussed with the doctor for more information.

Read more: Pregnancy and Crohn’s Disease or Ulcerative Colitis

What are the side effects/risks?

  • Increased risk of infection:
    • Because these medications target the immune system, they can affect the body’s susceptibility to infections.
  • Decreased white blood cell count and liver injury:
    • 6-MP and Imuran can cause a temporary drop in white blood cell cells and an increase in liver enzymes. This effect is reversible when the drug is stopped.
  • Pancreatitis
    • This is an allergic reaction that causes inflammation of the pancreas. Signs and symptoms include severe abdominal pain, nausea, and vomiting. This reaction is entirely reversible when the drug is stopped.
  • Lymphoma
    • These medications may be associated with an increased risk of developing a blood type cancer called lymphoma, but this is very rare. For example, the risk of developing lymphoma in the general population on no medications is approximately 1 in 10000. These medications may increase that risk to 4 in 10000.

Can I drink alcohol while on this medication?

Yes, but it is important to consume in moderation as the combination of these drugs and alcohol can increase stress on the liver.

Other Considerations

  • Because 6-MP and Imuran can affect your blood cell count and liver enzymes, it is necessary to go for bloodwork regularly to monitor for these side effects. It is recommended to do a blood test every 2 weeks for 2 months, and then every month for 2 months, and thereafter every 2-3 months while on therapy.
  • Ensure all vaccinations are up to date. When taking these medications, all live vaccines must be avoided.
  • For women, it is important to receive annual pap tests, even if previous exams have been negative.

Read more: Other treatments for Crohn’s or for colitis

ead more: Other treatments for Crohn’s or for colitis


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Treating ulcerative colitis and Crohn's disease. Major changes in the past 20 years.

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