Solving the IBS Riddle

By Kate H. Gamble, Senior Editor
Published Online: Tuesday, April 12, 2011
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Editor's Note: In recognition of IBS awareness month, we've provided current information on drug treatments for the condition, along with links to more resources.



By Kate H. Gamble, Senior Editor

For years, irritable bowel syndrome (IBS) has been a thorn in the side of patients, physicians, and pharmacists.

Defined as a gastrointestinal disorder characterized by recurring symptoms of abdominal pain, bloating, and altered bowel function in the absence of structural, inflammatory, or biochemical abnormalities, IBS is difficult to diagnose and often doesn’t respond to treatment.

For patients, learning how to manage the condition can be an ordeal. However, findings from a study published in the New England Journal of Medicine may offer hope for those who suffer from IBS.

Research has shown that IBS patients make more visits to physicians, undergo more diagnostic tests, are prescribed more medications, miss more workdays, have lower work productivity, are hospitalized more frequently, and account for greater overall direct health care costs than patients without the condition, according to the American College of Gastroenterology.

All of this can have a severe impact on quality of life, making it all the more critical that the condition is properly treated.

The problem is that IBS is a symptom complex. Because no reliable markers have been identified, the effects of pharmacotherapy are typically assessed by asking patients to report whether their symptoms were adequately relieved.

IBS, as many pharmacists can attest, can be challenging.

Current pharmacologic treatments—which include antispasmodics, antidepressants, antidiarrheals, serotonin reuptake inhibitors, probiotics, antibiotics, over-the-counter supplements, laxatives, complementary and alternative treatments, and lifestyle changes—are aimed at relieving the predominant GI symptom. The goal, however, should be to improve overall symptoms, including altered stool frequency and consistency, abdominal pain and discomfort, bloating, and quality of life.

This is where most treatments fall short, according to the authors of the NEJM study, who conducted 2 investigations to determine the efficacy of the antibiotic rifaximin (Xifaxan) as a treatment for IBS.

Lead author Mark Pimentel, MD, of Cedars-Sinai Medical Center in Los Angeles, CA, and colleagues hypothesized that gut flora may play a key role in the pathophysiology of IBS. In 2 identically designed, phase 3, double-blind, placebo-controlled trials, patients who had IBS without constipation were randomly assigned to either rifaximin at a dose of 550 mg or placebo, three times daily for 2 weeks, and were followed for an additional 10 weeks. The primary endpoint was the proportion of patients who had adequate relief of global IBS symptoms, while the key secondary endpoint was the percentage of patients who had adequate relief of IBS-relating bloating.

The investigators found that significantly more patients in the rifaximin group than in the placebo group had adequate relief of global IBS symptoms during the first 4 weeks after treatment, and that more patients in the rifaximin group had adequate relief of bloating. In addition, significantly more patients in the rifaximin group had a response to treatment as assessed by daily ratings of IBS symptoms, bloating, abdominal pain, and stool consistency.

“These results support the idea that intestinal microbiota or gut bacteria may be an underlying cause of IBS, and altering gut bacteria by treatment with rifaximin appears to be an effective way of providing relief to those who suffer from IBS symptoms,” said Yehuda Ringel, MD, an associate professor of medicine in the UNC School of Medicine and a co-author of the studies, in a press release.

The authors also noted that the antibiotic effect of rifaximin is most likely responsible for its efficacy in reducing the symptoms of IBS. Although there is some debate over which antibiotic effect is most important, they believe that rifaximin appears to target the cause of IBS rather than just treating the symptoms—a finding that could have significant implications for the treatment of IBS patients.

Although these studies offer promising data, it is important to remember that because of the complexities involved in diagnosing and treating IBS, there are still many patients who opt for self-treatment, often with OTC products. The role of the pharmacist in determining whether self-treatment is appropriate, and advising patients with IBS about the use of medications to treat their symptoms, is critical.

For more information:
In the video below, Larry Schiller, MD, a gastroenterologist based in Dallas, Texas, discusses the mechanism and effectiveness of several treatment options for IBS, including fiber therapy, antispasmodic drugs, lubiprostone, alosetron and anti-depressant drugs.



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