DEAR MAYO CLINIC:

I've read that persistent low-grade inflammation is present in some people with irritable bowel syndrome, and a few studies have reported on the potential benefits of medications that may target this aspect of IBS. Are these medications available to IBS patients? If not, is there a chance they will become available?

ANSWER:

Researchers have investigated the role that inflammation plays in irritable bowel syndrome (IBS). Studies have suggested that inflammation caused by an infection may trigger IBS symptoms and certain people who have IBS may have some ongoing inflammation. But research examining the effectiveness of anti-inflammatory medications in controlling IBS symptoms hasn't shown any benefit. As a result, anti-inflammatory drugs are not generally used to treat IBS.

IBS is a disorder that affects the large intestine (colon) and is characterized by symptoms such as diarrhea, abdominal pain, cramps, gas, bloating and constipation.

The intestinal walls are lined with layers of muscle that contract and relax in a coordinated rhythm as they move food through the intestinal tract. In some cases of IBS, these contractions are stronger and last longer than normal. Food is forced through the intestines too quickly, causing gas, bloating and diarrhea (diarrhea-predominant IBS). In other cases, the opposite occurs. Food moves through the intestinal tract too slowly, and stools become hard and dry (constipation-predominant IBS). Some people with IBS have a combination of both.

The underlying cause of IBS isn't known. Investigations into the cause have found that IBS may sometimes be triggered by an intestinal infection that involves severe diarrhea and inflammation of the colon. Those symptoms may cause changes within the colon that affect its function and lead to IBS. Ongoing inflammation has been observed in some people with IBS, particularly those with the diarrhea-predominant form of the disorder.

Based on this information, a study was conducted that examined the use of prednisolone, a corticosteroid medication that helps control inflammation, in treating IBS. However, no significant reduction in IBS symptoms was found in people who took prednisolone. Although anti-inflammatory medications are still under consideration in IBS research, currently no scientific evidence supports using these medications to treat IBS, and they are not part of mainstream IBS care.

Many people who have mild IBS symptoms don't require treatment with medication. Dietary and lifestyle changes, such as avoiding foods that trigger symptoms and reducing stress, are often enough to control IBS.

For those with moderate to severe IBS, medications targeted to control specific symptoms may be necessary. For example, tricyclic antidepressant medications such as imipramine and amitriptyline may be helpful in people who have diarrhea-predominant IBS with abdominal pain. These drugs can help slow colon function and reduce pain. Lubiprostone, a medication used to treat constipation, is also helpful for women older than 18 who have constipation-predominant IBS.

Medications now under investigation that appear to show promise in treating IBS include antibiotics, which are designed to fight infection; and probiotics, which introduce new and healthier forms of bacteria into the intestinal tract. Antibotics appear to be beneficial in some people whose IBS symptoms are due to an overgrowth of bacteria in the intestines. Probiotics seem to have a positive effect on the bacterial environment within the colon, leading to a reduction in symptoms in some people. These findings are preliminary, though, and more research is needed before antibiotics and probiotics become standard treatment for IBS.

If you have questions about the best treatment for IBS, talk to your doctor. Mild cases of IBS usually can be managed by a primary care physician. If you're having trouble controlling IBS symptoms with lifestyle and dietary changes alone, you may want to consult a gastroenterologist who has expertise in treating IBS and can help you develop a treatment plan to fit your circumstances. -- Michael Picco, M.D., Gastroenterology & Hepatology, Mayo Clinic, Jacksonville, Fla.

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