Irritable Bowel Syndrome Remains a Difficult Condition to Manage

Nicholas J. Talley, MD, PhD

In This Article

Bulking and Antigas Agents

Diet change is considered by many clinicians to be first-line therapy for patients with IBS.[1,2] Increasing dietary fiber intake is a relatively simple intervention, but many patients fail to implement this diet change. Furthermore, patients who do increase their fiber intake may experience a worsening of symptoms. Francis and Whorwell[5] found that the symptoms of 55 of 100 consecutive patients with IBS worsened on bran, with only 10 having any benefit, although this was an uncontrolled observation.

In a review by the ACG Task Force, 13 randomized controlled trials that evaluated the effectiveness of bulking agents were considered.[3] Ispaghula, a bulk-forming laxative commonly used in Europe, looked most promising based on the evidence; wheat bran has generally been disappointing.[3] Unfortunately, the quality of these trials was in the range of low to intermediate, and the results were mixed.[6,7,8,9,10,11,12,13,14,15,16,17,18] The task force concluded that fiber was not beneficial for the global IBS symptom complex ( Table 1 ).

In the most recent systematic review of 17 trials, fiber was more efficacious than placebo in terms of global IBS symptom relief.[19] Soluble fiber (psyllium, ispaghula, calcium polycarbophil) was bene ficial, but insoluble fiber (corn, wheat bran) was not.[19] Bulking agents probably do improve symptoms of constipation in IBS, even if abdominal pain or discomfort does not always improve significantly. Unfortunately, trials in primary care are lacking; thus the efficacy in this setting is unknown. The clinical impression that use of a bulking agent to help increase stool firmness in patients with diarrhea-predominant IBS has not been objectively confirmed.


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