IBS-D is a subtype of irritable bowel accompanied by loose or watery stool at least 25 percent of the time. IBS affects between 10-15 percent of adults in the U.S.
“For some people, IBS can be quite disabling, and no one medication works for all patients suffering from this gastrointestinal disorder,” said Julie Beitz, M.D., and FDA director for drug evaluation and research. “The approval of two new therapies underscores the FDA’s commitment to providing additional treatment options for IBS patients and their doctors.”
Viberzi (eluxadoline) activates receptors in the nervous system that can lessen bowel contractions, according to the FDA. In patient trials, Viberzi, which is intended to treat IBS-D specifically, was more effective in simultaneously reducing abdominal pain and improving stool consistency than placebo over 26 weeks of treatment. The drug is taken orally twice daily with food.
Xifaxan is approved for the treatment of abdominal pain and diarrhea in patients with IBS-D. It was originally intended for overseas travelers with diarrhea caused by E. coli. “The exact mechanism of action of Xifaxan for treatment of IBS-D is not known,” according to the FDA, “but is thought to be related to changes in the bacterial content in the gastrointestinal tract.”
The most serious known risk associated with Viberzi is the risk of spasm in the sphincter, which can result in pancreatitis. For Xifaxan, common side effects include nausea and an increase in alanine aminotransferase (ALT), a liver enzyme measured in blood.