Center for Inflammatory Bowel Disease Treatment and Research

6-mercaptopurine (6-MP, Purinethol®) and Azathioprine (Imuran®)

Generic Names: azathioprine and 6-mercaptopurine (or 6-MP)

Brand Names: Imuran® (azathioprine) and Purinethol® (6-mercaptopurine)

Drug Class: Immunosuppressant

What do these medications do? 6-MP (6-mercaptopurine or Purinethol®) and azathioprine (Imuran®) are maintenance medications used to help keep patients with Crohn’s disease or ulcerative colitis feeling well and off steroids. They work by decreasing the activity of the immune system, which results in decreased inflammation in the intestine. They may also help to close fistulas in patients with Crohn’s disease. These medications are slow acting, and can take up to 3 months to work.

At the time this medication is being started, your health care provider will order a blood test called TPMT to see how your/your child’s body will break down this medication. This test will help determine the correct starting dosage of medication, and it will take a few days to get the results.

How effective are 6-mercaptopurine and azathioprine for Crohn’s disease and ulcerative colitis? These medications are some of the most effective maintenance treatments we have for Crohn’s disease and ulcerative colitis. Studies suggest that approximately 75% of patients respond to these treatments. For most patients, “respond” means feeling well and coming off of prednisone.

What are the side effects? 6-mercaptopurine and azathioprine can temporarily lower the number of the body’s white blood cells, and this can put you/your child at risk for developing infections. These medications may also decrease the number of platelets in the blood which are necessary for proper clotting. Therefore, we will monitor your/your child’s blood counts and medication level closely, especially during the first three months of therapy. We may adjust the dose of medication depending on the blood counts and the medication level, so it is very important to follow your physician’s instructions for laboratory testing.

These medications can cause elevation of liver enzymes (hepatitis). This is seen in about 10% of patients, and usually responds to reducing the dose of medication. Your physician will monitor liver enzymes with your routine blood work. In addition, these medications can also cause inflammation of the pancreas (pancreatitis). Pancreatitis occurs in approximately 4% of patients within the first month and it can cause nausea, vomiting, and/or abdominal pain. It typically reverses once the medication is stopped. Other side effects 6-mercaptopurine and azathioprine can include nausea, vomiting, fever, and skin rash. Call your health care provider if you experience any of these or other side effects from these medications.

The use of immunosuppressant medications may slightly increase your/your child’s risk of developing lymphoma (a tumor of the lymph glands). The precise risk is unknown, but is estimated to be about 1/3000. This is a slight increase in risk over the other children and young adults of the same age who are not taking this medication.

How to take your medication and miscellaneous facts:

• You should take this medication at the same time everyday.
• Do not take this medication with milk, as it may decrease the absorption of the medication.
• You may take this medication with food.
• If you miss a dose, take it as soon as you remember.
• You/your child should not receive live vaccines (ex. MMR, chicken pox, nasal flu) while taking this medication. Inactivated vaccines (ex. tetanus and influenza shot) are safe. It is a good idea to call your doctor or nurse before receiving any vaccinations.
• Check with your doctor or nurse practitioner before starting any new medications, herbs, or vitamins while taking this medication.