LAS VEGAS, Nevada — Mesalamine improved abdominal pain and stool consistency in patients with irritable bowel syndrome with diarrhea, according to a study presented here at the American College of Gastroenterology 2012 Annual Scientific Meeting and Postgraduate Course.

The study was led by Jeffrey Aron, MD, director of the Center for Inflammatory Bowel Disorders at the California Pacific Medical Center in San Francisco. Dr. Aron, who presented the research, believes that stress can cause inflammation in these patients, bringing on symptoms. "It seemed to me that a medication that has been proven to be safe over the years for treating ulcerative colitis and Crohn's disease might be applicable to patients who have irritable bowel syndrome," Dr. Aron told Medscape Medical News.

The researchers conducted a randomized double-blind placebo-controlled multicenter study of mesalamine granules extended-release capsules in patients with irritable bowel syndrome with diarrhea (determined by Rome III criteria) but no constipation during a 7- to 13-day eligibility period. Over 12 weeks, 47 patients received once-daily mesalamine 750 mg, 51 received mesalamine 1500 mg, and 50 received placebo.

For abdominal pain, weekly response was defined as an improvement of 30% or more from baseline in the weekly average abdominal pain score. For stool consistency, weekly response was defined as a reduction of at least 50% from baseline in the number of days in a week with a stool consistency of type 6 or 7 on the Bristol Stool Scale.

Monthly responders were those patients who experienced weekly response in both abdominal pain and diarrhea for at least 2 of 4 weeks.

More patients in the 1500 mg group than in the placebo group were monthly responders for at least 3 months (47.1% vs 28.0%; P = .0432). There was no statistically significant difference between the 750 mg and placebo groups (31.9% vs 28.0%; P = .6059). There were no differences in the safety profiles of the groups, and demographics and baseline characteristics were similar.

"Inflammation isn't the only problem in these patients, but I think it's the major thing," Dr. Aron said. "This allows gastroenterologists approaching these patients to say: 'You're not crazy, and here's a safe and effective treatment'."

The study suggests that irritable bowel syndrome has an inflammatory component. "At least for a subgroup of patients, we may have something new to offer them," Ronald Vender, MD, professor of medicine at Yale School of Medicine in New Haven, Connecticut, told Medscape Medical News.

The study was funded by Salix Pharmaceuticals, which markets mesalamine. Dr. Aron reports receiving research funding from Salix and being a consultant to the company. Some of the study coauthors are employees of and report owning stock in Salix. Dr. Vender has disclosed no relevant financial relationships.

American College of Gastroenterology (ACG) 2012 Annual Scientific Meeting and Postgraduate Course: Abstract 7. Presented October 22, 2012.