Lubiprostone may improve symptom relief rates in adults with irritable bowel syndrome

May 22 2007

A new study demonstrated that the active ingredient in AMITIZA (lubiprostone), given 8 mcg twice a day, may improve symptom relief rates in adults with irritable bowel syndrome with constipation (IBS-C).

These results were presented as a late-breaker at Digestive Disease Week 2007, the largest annual international meeting of digestive disease specialists.

“In this study, patients receiving lubiprostone were nearly twice as likely to achieve an overall response from symptoms of IBS-C compared to those receiving placebo,” said Douglas A. Drossman, M.D., primary investigator, UNC Center for Functional GI and Motility Disorders, University of North Carolina, and the Chair of the Rome Committee. “As a result, lubiprostone may represent an important treatment for IBS-C sufferers.”

IBS is a condition that affects approximately 58 million Americans and accounts for 25-50 percent of referrals to gastroenterologists. IBS-C symptoms include abdominal pain or discomfort associated with defecation or a change in bowel habits with features of disordered defecation.

Lubiprostone is a novel selective chloride channel activator that has been shown to be effective and well-tolerated in a number of well-controlled clinical trials in patients with chronic idiopathic constipation. Lubiprostone is marketed in the U.S. as AMITIZA, a 24-mcg gelcap that was approved for use for chronic idiopathic constipation in adults on January 31, 2006.

Sucampo Pharmaceuticals expects to submit a supplemental New Drug Application for IBS-C to the U.S. Food and Drug Administration by July 2007.

In two phase III, multi-center, double-blind, randomized, placebo-controlled trials, 1,171 adults diagnosed with IBS-C (Rome II Criteria) were enrolled and received lubiprostone 8 mcg taken twice daily (783 adults) or placebo (388 adults) over a 12-week period.

Primary efficacy was determined by a unique question: “How would you rate your relief of IBS symptoms (abdominal discomfort/pain, bowel habits and other IBS symptoms) over the past week compared to how you felt before you entered the study?” A 7-point balanced scale with a strict evaluation using the two highest scale points to qualify as a responder was used. Patients were considered monthly responders if they reported at least moderate relief four out of four weeks or significant relief two out of four weeks. To qualify as an overall responder (the measure used in the primary endpoint), patients had to be a monthly responder for at least two out of three months. During the evaluation period, patients discontinuing for any reason or reporting an increase in rescue medication use, lack of efficacy or moderately or significantly worse relief were deemed non-responders. These responder rates may not be comparable to those in other studies since the new scale was more restrictive than those used in previous reports.

The findings demonstrated that patients receiving lubiprostone 8 mcg twice daily were nearly twice as likely to achieve overall response compared to those receiving placebo (lubiprostone 17.9 percent vs. placebo 10.1 percent, P=0.001). There was a similar incidence of serious adverse events (1 percent in each group) and related adverse events (lubiprostone 22 percent vs. placebo 21 percent) compared to placebo. The most common treatment-related adverse events (>5% of patients) were nausea (8 percent vs. 4 percent, respectively), diarrhea (6 percent vs. 4 percent, respectively) and abdominal pain (4 percent vs. 5 percent, respectively).

Irritable bowel syndrome (IBS) is a chronic disorder characterized by abdominal discomfort and pain, and bowel habit changes including symptoms of constipation and/or diarrhea. The condition can significantly interfere with daily activities and reduce patients' quality of life, resulting in absences from school, missed work and reduced productivity.

Three main types include IBS with constipation (IBS-C), with diarrhea (IBS-D) and with mixed symptoms of constipation and diarrhea (IBS-M). In IBS-C, symptoms are present for at least 3 days per month over a 3-month period. Although people with IBS-C report suffering from many of the same symptoms associated with constipation, the presence of abdominal discomfort and pain is what differentiates IBS-C from chronic constipation. Additionally, the hypersensitivity of the gastrointestinal system of individuals with IBS makes them more prone to experience the effects of even mild symptoms of constipation or diarrhea. The condition is approximately 2 to 2.5 times more prevalent in women than men, and women are more likely to report a history of constipation.