Many patients may soon find relief from the bloating, cramping, abdominal pain and constipation associated with irritable bowel syndrome, or IBS.
Lubiprostone, known by the brand name AMITIZA®, was just approved by the U.S. Food and Drug Administration for use in women with IBS plus constipation, thanks in part to University of Michigan Health System research that demonstrated the safety and efficacy of the drug for treatment of IBS-C.
Led by U-M gastroenterologist William D. Chey, M.D., the studies show that lubiprostone significantly improves all of the symptoms associated with IBS-C in many women.
Results from these studies will be presented on May 18 and May 19 at Digestive Diseases Week in San Diego.
"We found that individuals who were treated with AMITIZA were nearly twice as likely to experience improvement in their IBS symptoms compared to individuals who were treated with placebo," says Chey, director of the Gastrointestinal Physiology Laboratory and professor of internal medicine at the U-M Medical School. "Right now, it is the only FDA-approved treatment available that addresses the entire clinical spectrum of symptoms related to IBS-C."
IBS, an often painful disorder of the lower intestine, affects between 10 to 15 percent of the U.S. population.
While IBS is the second-leading cause of work absenteeism behind the common cold, Chey says fewer than half of patients with IBS seek medical treatment. And, he says, most over-the-counter medicines commonly used to treat symptoms -- fiber, laxatives and stool stimulants -- don't address the bloating and pain associated with IBS.
Most patients with IBS tend to fall into two categories: IBS-C or IBS with diarrhea. IBS-C is more common among older adults, while IBS-D tends to be seen more in younger patients.
Since the majority of patients with IBS are women, studies involving IBS tend to be made up of predominately female participants -- more than 80 percent in most cases, Chey estimates.
"Although AMITIZA is only approved for use in women with IBS-C, it doesn't mean that the drug doesn't work for men. Unfortunately, we just haven't had enough men represented in these studies to make a firm decision on treatment using this drug," notes Chey.
The supplemental New Drug Application for AMITIZA -- which also is approved by the FDA for treatment of chronic idiopathic constipation -- was based on two phase III, multi-center trials involving 1,154 participants. These trials compared lubiprostone versus a placebo during the course of 12 weeks. Each participant kept an electronic diary to report weekly outcomes of IBS-C symptoms.
After one week, 20 percent of the lubiprostone participants reported moderate to significant relief of symptoms. By week four, 32 percent said they experienced relief of global IBS-C symptoms -- abdominal pain, bloating, constipation severity and straining during bowel movements. Lubiprostone also improved stool consistency.
Additionally, Chey will present findings at DDW from a follow-on study related to the two phase III trials. This 48-week study looked at the efficacy and safety of lubiprostone. Many of its 476 participants also took part in the phase III trials. For this study, however, participants all received lubiprostone; no placebos were given.
The study found that lubiprostone is effective and well tolerated in adults with IBS-C for up to one year. The spectrum of symptoms that constitute IBS-C, including abdominal pain and discomfort, bloating and constipation-related complaints, significantly improved during the 48-week treatment period. The most common treatment-related adverse events among the study groups were nausea and diarrhea.
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