Mercaptopurine (6-MP) for Ulcerative Colitis: What You Should Know | MyCrohnsAndColitisTeam (2024)

If your gastroenterologist has recommended mercaptopurine (6-mercaptopurine or 6-MP) to treat your ulcerative colitis, you likely have questions about the medication. You may be wondering how it works, what side effects it can cause, and whether it’s a good option for you. Mercaptopurine is a common treatment for inflammatory bowel disease (IBD), and more than 3,400 members of MyCrohnsAndColitisTeam report taking it.

Knowing key points about IBD medications can help you feel more confident about working with your doctor to make treatment decisions. Read on to find out what you should know about mercaptopurine, including when it might be recommended, how long it takes to start working, and potential risks and side effects.

What Is Mercaptopurine?

Mercaptopurine (sold as Purinethol and Purixan) is an immunomodulator. This means it regulates the immune system. Immunomodulators are important for autoimmune diseases like ulcerative colitis as they help prevent the overactive immune system from attacking healthy tissue.

Scientists believe mercaptopurine works by interfering with T cells, a type of white blood cell that can cause inflammation in people with IBD. By controlling T cells, mercaptopurine helps prevent them from attacking the digestive system and causing damage and ulcerative colitis symptoms.

Mercaptopurine and Steroids

You might hear mercaptopurine being described as a “steroid-sparing” drug. This is because mercaptopurine reduces the need for long-term steroid use. Corticosteroids (or simply steroids) are a common treatment for people with IBD, especially during flare-ups.

When Is Mercaptopurine Used for Ulcerative Colitis?

Mercaptopurine may be recommended to treat ulcerative colitis that hasn’t responded to other treatments. Mercaptopurine is more often prescribed to achieve and maintain remission (when you have no symptoms, or symptoms are greatly reduced) in people with moderate to severe ulcerative colitis.

For someone who’s taken azathioprine (Imuran) — a drug similar to mercaptopurine — and experienced side effects, a doctor may prescribe mercaptopurine to see if they’re better able to tolerate it.

How Is Mercaptopurine Taken?

Mercaptopurine is taken orally, as a pill. It’s usually prescribed to be taken once or twice a day. A doctor may prescribe it alone or in combination with another drug to make it more effective.

How Long Is Mercaptopurine Taken?

Mercaptopurine is generally taken on a long-term basis to help maintain remission. If mercaptopurine effectively reduces your symptoms, you may be on it for years. During this time, your doctor might recommend regular blood tests or other exams to make sure the treatment is still safe and effective for you.

Several MyCrohnsAndColitisTeam members report being on mercaptopurine for several years with good results. “I was on mercaptopurine (6-MP) for 19 years. It’s kept my IBD in remission. I’m no longer taking it and so far have had no flare-ups,” one member shared.

“Mercaptopurine has kept me out of the hospital for years,” another wrote.

If you’ve been taking mercaptopurine and stayed in remission for a long time without a flare-up, your gastroenterologist might have a discussion with you about whether it’s necessary to continue taking it.

Always talk to your gastroenterologist before making changes to the way you take your IBD medication, even if you don’t have symptoms. Ask any questions you may have about if and when you can stop taking mercaptopurine.

How Long Does Mercaptopurine Take To Start Working?

It can take three to six months after starting mercaptopurine before you start to feel better. When you first begin taking it, be patient — stick to your treatment plan, even though it might not seem to be doing anything in the beginning. Do report any side effects you notice to your gastroenterologist to see whether a different dosage or medication is needed.

Potential Side Effects of Mercaptopurine

Every medication, even those sold over the counter, can potentially cause side effects. It’s important to remember that not everyone will experience every possible side effect from a drug. Common side effects of mercaptopurine include:

• Nausea and vomiting
• Headache
• Diarrhea
• Fatigue or feeling unusually tired
• Fever
• Skin rash and mouth sores
• Aches and pains, including joint pain

Talk to your gastroenterologist if you experience side effects from mercaptopurine. Sometimes medication side effects are tolerable or at least more tolerable than untreated IBD symptoms. However, if side effects from mercaptopurine are impacting your day-to-day life, your gastroenterologist may recommend changing your dose or switching treatments.

Special Considerations When Taking Mercaptopurine

Like with any new medication, it’s important to be aware of special considerations around taking mercaptopurine, such as whether it’s safe to take with certain medications or when pregnant. When in doubt about whether a specific circ*mstance or medication precludes you from taking mercaptopurine, talk to your gastroenterologist.

Other Medications

Make sure your health care team knows about all other medications you’re taking (including over-the-counter ones), as well as supplements, herbal medicines, or complementary therapies. Some medications can cause interactions with mercaptopurine and lead to adverse effects. For example, medications that might interact with mercaptopurine include:

• Certain antibiotics
• Warfarin (a blood thinner used to treat blood clots)
• Febuxat or allopurinol (medications for gout)

Pregnancy and Breastfeeding

If you’re pregnant, plan to become pregnant, or are currently breastfeeding, talk to your gastroenterologist about whether it’s safe to take mercaptopurine.

Vaccinations

It’s important to talk to your doctor before getting a vaccination while taking mercaptopurine, or even after you’ve stopped taking it. Medications that can affect your immune system, such as mercaptopurine, may decrease the effectiveness of vaccinations.

Rare but Serious Side Effects and Negative Reactions

Along with common side effects, mercaptopurine can sometimes contribute to more serious side effects such as:

• Infection
• Pancreatitis (inflammation of the pancreas)
• Skin cancer
• Lymphoma

Some MyCrohnsAndColitisTeam members have experienced some of these side effects. “Mercaptopurine gave me pancreatitis almost immediately,” one member wrote in response to another’s question about mercaptopurine side effects.

“I was on mercaptopurine (aka 6-MP, Purinethol) for 14 years,” wrote another. “It worked wonders for me. Unfortunately, it may have contributed to a form of leukemia/lymphoma that is quite rare in adults, and so I quit once I began chemotherapy.”

Some people may show immediate signs of a negative reaction when they first begin taking mercaptopurine. Call a doctor right away if have any of the following symptoms after taking mercaptopurine:

• You see signs of an allergic reaction (rash, hives).
• Your hands, feet, mouth, or lips are swollen.
• You have difficulty breathing or swallowing.

Your gastroenterologist can help you better understand your personal risk for serious side effects based on your individual health history.

Talk to Your Gastroenterologist About Mercaptopurine

There’s a lot of information around mercaptopurine, and it’s understandable if you feel a little overwhelmed. Remember that your gastroenterologist and health care team are there to talk through any questions or concerns you may have. Starting a new medication can be scary, but knowing what to expect can help you feel more informed and confident about navigating any ups and downs as you find the right ulcerative colitis medication for you.

Talk With Others Who Understand

MyCrohnsAndColitisTeam is the social network for people with ulcerative colitis and Crohn’s disease and their loved ones. On MyCrohnsAndColitisTeam, more than 182,000 members come together to ask questions, give advice, and share their stories with others who understand life with ulcerative colitis and Crohn’s disease.

Have you taken mercaptopurine to treat your ulcerative colitis? What would you want others with ulcerative colitis to know about it? Share your experience in the comments below, or start a conversation by posting on your Activities page.