By Tara Baukus Mello

Medically reviewed by Jonathan Hansen, MD, PhD

There are two immunomodulators (immune-system-suppressing drugs taken in pill form) that are commonly used for the treatment of IBD: azathioprine (AZA, brand names Imuran and Azasan) and 6-mercaptopurine (6-MP, brand name Purinethol). (Other oral immune system suppressors that are sometimes used for IBD include cyclosporine, tacrolimus, and methotrexate.)

Because AZA and 6-MP literally suppress your immune system, a big concern is that your risk of infection will be increased. As a result, IBD experts suggest that you try to prevent infections as much as possible by staying up-to-date on all recommended vaccines, including those for influenza and pneumonia, as well as taking preventive measures like thoroughly washing your hands and avoiding being around sick people as much as possible.

6 Possible Side Effects

AZA and 6-MP are very similar chemically. Side effects from them are rare, affecting fewer than 5% of people. Possible side effects that may occur within days or weeks after starting these drugs include:

  • Headaches
  • Body aches
  • Fever
  • Nausea
  • Vomiting
  • Abdominal pain

If you experience any of these symptoms, notify your doctor immediately, since they may indicate a serious condition like pancreatitis.

Long-Term Concerns to Be Aware Of

In addition, there are some other side effects that can occur after a longer time on immunomodulators. These often are detected only by astute doctors—and by patients who are watching for them. These long-term side effects include liver inflammation, low blood counts, infections, and, rarely, certain types of cancer.

Since these drugs have the potential to lower blood counts to dangerous levels—or cause liver inflammation without any noticeable symptoms—if you’re taking immunomodulators, it would be wise to have your blood counts and liver enzymes checked regularly by your doctor using simple blood tests.

Last, but not least, these drugs have been associated with a slight increase in the risk of certain types of cancer. In a large study of over 100,000 IBD patients, those who used these drugs were about twice as likely to be diagnosed with certain types of skin cancer (basal cell carcinoma and squamous cell carcinoma) as people not taking these drugs. While these kinds of cancer typically are easily detected and treated by a dermatologist, it’s a good idea to always wear sunscreen when out in the sun for long periods. In addition, there is a similarly small risk of these drugs causing lymphoma, a type of blood cancer, and this risk increases slightly in people over 50 years old.

Despite these rare side effects, 6-MP and AZA remain a mainstay of IBD treatment because their effectiveness often outweighs their risks; however, it is important to discuss the pros and cons of using these medications with your doctor.

Medical reviewer and Oshi physician-partner Jonathan Hansen, MD, PhD, has been involved in 20-plus clinical trials of investigational compounds that target various pathways important in the development of IBD. He has co-authored book chapters on IBD and been published in a variety of peer-reviewed journals, and his interests include the role of environmental bacteria in the development of chronic intestinal inflammation. Dr. Hansen serves as an Associate Professor of Medicine in the Division of Gastroenterology & Hepatology at the University of North Carolina at Chapel Hill. He received his BS in Biochemistry from Brigham Young University, and his MD and PhD in Microbiology and Immunology from Indiana University School of Medicine.

Oshi is a tracking tool and content resource. It does not render medical advice or services, and it is not intended to diagnose, treat, cure, or prevent any disease. You should always review this information with your healthcare professionals.