Spotlight on irritable bowel syndrome

Recent research reviewed the interaction between diet and gut microbiota in irritable bowel syndrome (IBS), explored the varying daily challenges facing patients with different IBS subtypes, and tested the safety and efficacy of two medications to treat IBS symptoms.

First, a review article focused on the role of diet both in the pathophysiology of IBS and as a tool that improves symptoms and quality of life. An interaction between diet, gut microbiota, and gut endocrine cells may play an important role in the pathophysiology of IBS, according to the paper, which was published online on Aug. 7 by Nutrients as part of a special issue focusing on nutritional management of gastrointestinal diseases and disorders.

While the intake of a diet low in fermentable oligo-, di-, monosaccharides, and polyols (FODMAPs) improves both symptoms and quality of life in patients with IBS, only 50% to 70% of IBS patients see an effect of the diet, which is expensive, difficult to maintain long-term, and may negatively change the intestinal microbiota, according to the article. In contrast, a NICE (National Institute for Health and Care Excellence)-modified diet has the same effect as a low-FODMAP diet, is easy to maintain, and is now the diet first recommended to patients with IBS, the review authors said. “In our clinic, we use a slightly modified NICE diet, as recommended by the British Dietetic Association,” which includes regular meals; replacing wheat products with spelt products; reducing intake of fatty food, onions, cabbage, and beans; avoiding soft drinks, carbonated beverages, chewing gum, and sweeteners that end with -ol; and regular intake of psyllium husk fibers, the authors wrote. “Patients who do not respond well to diet management should be considered as candidates for gut microbiota alteration through [fecal microbiota transplantation],” they concluded.

Second, researchers assessed patient-reported effects of IBS symptoms on productivity, as well as the differences between patients with constipation-predominant or diarrhea-predominant IBS (IBS-C and IBS-D, respectively). The industry-funded study was based on the Life with IBS survey, an online survey conducted from September through October 2015 for the American Gastroenterological Association. Respondents met Rome III criteria for IBS-C or IBS-D. Results were published online on Aug. 13 by Clinical Gastroenterology and Hepatology.

Of 3,254 participants (mean age, 47 years; 81% women), 1,885 who were employed or in school reported that IBS symptoms affected their productivity an average of 8.0 days each month and that they missed about 1.5 days of work or school each month because of IBS. More than half of participants reported that their symptoms were very bothersome. Those with IBS-C were more likely than those with IBS-D to report avoiding sex, having difficulty concentrating, and feeling self-conscious, and those with IBS-D reported more avoidance of places without bathrooms, difficulty making plans, avoidance of leaving the house, and reluctance to travel. Between-group differences remained after controlling for symptom bothersomeness, age, sex, and employment status. In exchange for one month of relief from IBS, more than half of participants reported they would be willing to go one month without caffeine or alcohol, 40% would give up sex for a month, 24.5% would give up cell phones for a month, and 21.5% would give up the internet for a month. Limitations include the fact that patients with IBS mixed type (IBS-M) were not included and the possibility of sampling and recall bias due to the online survey design, the study authors noted.

Third was a double-blinded phase 4 study of eluxadoline in patients who reported inadequate symptom control with loperamide. Researchers randomly assigned 346 adults (mean age, 44 years; 70% women) with IBS-D (Rome III criteria) to eluxadoline (100 mg twice daily) or placebo for 12 weeks at 82 sites in the U.S. and Canada from November 2016 to January 2018. Baseline patient characteristics and IBS-D symptoms were similar between the two groups. Patients without a gallbladder were excluded, as the drug is contraindicated due to an increased risk of developing pancreatitis and/or sphincter of Oddi spasm. The primary endpoint was the proportion of participants who met daily composite response criteria (≥40% worst abdominal pain improvement and <5 Bristol Stool Scale score) for at least 50% of treatment days and who recorded 60 or more days of diary entries over the study period. Results of the study, which was sponsored by the drug manufacturer, were published online on July 26 by the American Journal of Gastroenterology.

A total of 295 (85.3%) patients completed the trial. Compared to participants receiving placebo, a greater proportion of those receiving eluxadoline achieved the composite responder endpoint (22.7% vs. 10.3%; P=0.002), as well as the component endpoints of improvements in stool consistency (27.9% vs. 16.7%, P=0.01) and worst abdominal pain (43.6% vs. 31.0%, P=0.02). Rates of adverse events were comparable between groups (37.4% with eluxadoline vs. 35.3% with placebo), and there were no reported treatment-related serious adverse events or cases of pancreatitis or sphincter of Oddi spasm. “The positive outcomes of this study in a real-world setting suggest that eluxadoline may be an option for those who have previously used loperamide,” the study authors wrote.

Finally, a double-blind, industry-supported trial assessed the safety and efficacy of PB+S (pinaverium bromide [100 mg] plus simethicone [300 mg]) in patients with IBS (Rome III criteria) and abdominal pain/discomfort for at least two days within the week prior to baseline assessment. Participants were screened between November 2008 and December 2009. Researchers randomized 285 patients (mean age, 36.5 years; 83% women) to receive PB+S or placebo over 12 weeks. The primary endpoint was overall symptom improvement, which participants reported weekly on a Likert scale. Results were published online on Aug. 2 by the Journal of Clinical Gastroenterology.

There was no significant difference between groups in overall symptom improvement (effect size, 20% in favor of PB+S; P=0.13), However, the PB+S group had significantly greater improvements in abdominal pain (effect size, 31%; P=0.038) and bloating (effect size, 33%; P=0.019) than the placebo group. There was also more improvement in frequency of Bristol Stool Scale types 3 to 5 in the PB+S group compared to the placebo group, mainly in patients with IBS-C and IBS-M. A limitation of the trial is that participants older than age 50 years were not included, so results cannot be extrapolated to this patient population, the authors noted. “Achievement of effect sizes >30% are of relevance particularly for treatments addressing functional gastrointestinal disorders, wherein a significant improvement attributable to placebo can be expected,” they wrote.