Mercaptopurine for Crohn's disease and ulcerative colitis

What is mercaptopurine?

Mercaptopurine is part of a group of medications known as thiopurines which are immunosuppressants. This means they work to reduce the activity of the immune system. Mercaptopurine is chemically very similar to azathioprine, though in the UK azathioprine is used more widely than mercaptopurine.

It is used in the treatment of Crohn’s disease and ulcerative colitis but is also used to treat acute lymphocytic leukemia, a type of cancer that begins in the white blood cells. It is not usually the first medication given to people with inflammatory bowel disease (IBD) but is used to help people come off of steroids and to maintain remission. For this reason it is often referred to as ‘maintenance therapy’ and can be taken long-term. It is also used to help in the treatment of fistulas.

How is mercaptopurine taken?

It is taken in tablet form, usually once a day. You may be told to take it on an empty stomach one hour before food or three hours after eating. You should avoid taking mercaptopurine at with cow’s milk as it contains high levels of xanthine oxidase which can inactivate mercaptopurine.

The dosage you will be given will depend on your weight and disease severity.

Mercaptopurine is a slow-acting medication and can take between 3-6 months to work. This means you may need to take another medication, such as steroids, at the same time to control your symptoms.

What are the different types of mercaptopurine available?

Mercaptopurine is often referred to as 6-mercaptopurine, 6-MP or Purinethol.

Can mercaptopurine be taken with other medication?

There are some medications which can interact with mercaptopurine. These include:

You should inform your doctor of any medications or supplements you are taking to ensure they do not react with your new medication.

Mercaptopurine is sometimes prescribed at the same time as biologic medications - such as adalimumab or infliximab. This is known as combination therapy.

Before starting your treatment you will receive a number of tests. One of these will look at the level of enzymes in your body. If you have a high level of enzymes then you may be prescribed allopurinol to be taken at the same time as mercaptopurine as these enzymes can cause side effects of the medication.

Are there any potential side effects of mercaptopurine?

As with all medications some people experience side effects when taking mercaptopurine. Some of the more common side effects reported include:

More serious side effects include:

You should tell your doctor if you experience any side effects.

Is there anything I should know before taking mercaptopurine?

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