Arthritis and the GI Tract

TNF inhibitors, biologic drugs that target a specific protein (TNF) tied to inflammation, are commonly used to treat a number of inflammatory conditions, including rheumatoid arthritis (RA). They’re also often used to treat inflammatory bowel disease (IBD), which includes Crohn’s disease and ulcerative colitis. While drugs in this class have drastically helped to improve the lives of many people, a new study suggests that they may have this downside: People who take them for a non-gastroenterological condition (like RA) appear to be more likely to develop Crohn’s or ulcerative colitis.

TNF inhibitors are already known to have some major side effects, namely that they interfere with the immune response in such a way that they increase your chances of getting serous infections and can increase your risk of certain cancers. But this finding adds a different twist, as it suggests that these drugs might raise the risk of some of the same conditions that they’re designed to treat.

The study, which was published in the journal Alimentary Pharmacology and Therapeutics, doesn’t prove that TNF inhibitors cause IBD in people with inflammatory arthritis. But researchers found that people with RA, psoriasis, psoriatic arthritis, or ankylosing spondylitis who took TNF inhibitors were more likely than those with the same autoimmune ailments who did not take them to later develop IBD.

The study, which was based on data from two Danish health registries, included more than 17,000 patients with autoimmune disease (not including IBD) who had used anti-TNF drugs and more than 63,000 who had not taken them.

Most patients in the registries who had used TNF inhibitor drugs had taken etanercept (Enbrel), infliximab (Remicade), and/or adalimumab (Humira). For reasons that aren’t clear, only etanercept had a strong link to IBD: People who used it were twice as likely as those who did not use any TNF inhibitor to develop Crohn’s or ulcerative colitis during the course of the study.

While this seems alarming, the total number of people in any of the groups who developed IBD with was fairly small, so it doesn’t mean that everyone with RA has to avoid etanercept. Other factors that were not considered in this study, such as family history or other IBD risk factors, might also play a role.

It’s also worth noting that etanercept is not one of the TNF drugs that are approved for treating IBD (though others in this class are).

“Our study adds to the complexity of the understanding across underlying autoimmune disease, type of anti‐TNFα therapies, and adverse reactions,” the authors wrote. While more research is warranted, “the recognition of these clinical problems is critical for physicians caring for individuals being treated with anti‐TNFα agents to minimize risk and provide optimal care.”

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