Treating the Irritable Bowel Syndrome: What Really Works?

abstract & commentary

Synopsis: Contrary to popular belief, bulking agents failed to pass muster while the use of smooth-muscle relaxants was supported by evidence from clinical trials.

Source: Jailwala J, et al. Ann Intern Med 2000;133:136-147.

Jailwala and colleagues set out to evaluate the efficacy of pharmacologic agents for irritable bowel syndrome (IBS). Their analysis was based on a review of 70 randomized, double-blind, parallel, or cross-over trials of a pharmacologic intervention for adult patients that reported outcomes of improvement in global or irritable bowel-specific symptoms. They found that the strongest evidence for efficacy was shown for smooth-muscle relaxants in patients with abdominal pain as the predominant symptom. Loperamide seemed to reduce diarrhea but did not relieve abdominal pain. They concluded that the efficacy of bulking agents had not been established. They also felt that evidence for the use of psychotropic agents was inconclusive and that more high-quality trials of longer duration were needed. There was also evidence to support efficacy for 5-HT-receptor antagonists, but they felt that more studies were needed.

Comment by Eamonn M. M. Quigley, MD

IBS continues to pose a therapeutic challenge. Given that the etiology of this common disorder remains unclear, therapy remains largely symptomatic with fiber and bulking agents being recommended for constipation, antispasmodics for pain, and antidiarrheals for those with diarrhea. Recently, antidepressants have become popular, based primarily on their proposed effects on visceral sensation; more recently, alosetron, a 5-HT3-antagonist, has been approved for use in IBS in the United States, as a gut-specific anti-nociceptive agent.1 This excellent review attempts to place these therapies in context through a rigorous review of evidence of efficacy. On review, many studies were found to exhibit methodological and analytical shortcomings; most were far from adequately powered and evaluated short-term therapy only. Indeed, the number of truly high-quality studies in this area proved to be remarkably few. Contrary to popular belief, bulking agents failed to pass muster, while the use of smooth-muscle relaxants was supported by evidence from clinical trials. Other agents, including anti-depressants, were difficult to assess due to a lack of high-quality studies. Initial studies with alosetron looked promising. Jailwala et al did not assess psychological or behavioral approaches. Clearly, IBS deserves further rigorous attention from the clinical trialist; we need both better studies on available agents and new studies with better agents.

Reference

1. Quigley EMM. Int Med Alert 2000;22:81-82.