Irritable Bowel Syndrome Remains a Difficult Condition to Manage

Nicholas J. Talley, MD, PhD

Disclosures
In This Article

Abstract and Introduction

Irritable bowel syndrome (IBS) remains challenging to manage, with no universally agreed treatment protocol. Complicating the treatment picture is the placebo response, which can vary from 20% to 70% and can be sustained long term. Results of the most recent meta-analysis on fiber intake suggest that soluble fiber (psyllium, ispaghula, and calcium polycarbophil) is of benefit in alleviating IBS symptoms, while insoluble fiber (corn and wheat bran) is not. A meta-analysis of antispasmodic agents suggests that the use of this class of drugs improves global symptoms in IBS and reduces abdominal pain, but the anticholinergic drugs available in the United States have limited efficacy. Opioid agonists are effective antidiarrheal agents; loperamide is superior to placebo for IBS-associated diarrhea but not other symptoms. Meta-analyses support the efficacy of tricyclic antidepressants, but the efficacy of the selective serotonin reuptake inhibitors is unclear. Tegaserod is efficacious in constipation-predominant IBS in women. Alosetron is efficacious in women with diarrhea-predominant IBS, but side effects limit its use. A number of newer agents are being tested, but which of these will reach the clinical setting remains uncertain.

Irritable bowel syndrome (IBS) represents a symptom complex comprising abdominal discomfort or pain associated with disturbed defecation, often coexisting with bloating.[1,2] A number of pathophysiologic abnormalities have been identified in IBS, but the exact cause remains unknown and treatment is largely empirical.[1] IBS is a highly prevalent condition, affecting approximately 10% of US adults, and it can be disabling.[1,2] In part, the disability results from the inability of patients to predict when their symptoms will occur; they may often experience unplanned interruptions to work and home activities because of physical discomfort and shame.

Specific symptom-based criteria, such as the Rome criteria, have been developed for IBS that allow clinicians to make a positive diagnosis, particularly in the absence of red flags, or alarm features, such as weight loss, GI bleeding, or vomiting.[1,2] The American College of Gastroenterology (ACG) Functional Gastrointestinal Disorders Task Force concluded that patients with IBS who present for care typically have impaired quality of life and deserve to be offered treatment; the goal, then, is to improve global symptoms of the condition.[3]

IBS symptoms tend to come and go, which may account for some of the relatively high–and varied–placebo responses observed in clinical trials, ranging from 20% to 70%.[2] Furthermore, in a 12-month trial of alosetron versus placebo, it is striking that the placebo response was maintained for at least 12 months, which is as yet unexplained.[4] However, a clinical trial represents an artificial setting. The efficacy of the placebo response in IBS in clinical practice is unknown and is likely to be substantially lower than that which has been reported in the trials.

Some drugs have a significant place in the management of IBS, although evidence that many of the therapies used are superior to placebo remains lacking. This review will focus on results of published randomized controlled trials to assess the evidence of drug efficacy in IBS.

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