The US Food and Drug Administration (FDA) approved Viberzi (eluxadoline) and Xifaxan (rifaximin), two new treatments, manufactured by Patheon Pharmaceuticals, Inc. and Salix Pharmaceuticals, Inc. respectively, for irritable bowel syndrome with diarrhoea (IBS-D) in adult men and women.  

According to the National Institutes of Health, patients with irritable bowel syndrome (IBS) experience a number of signs and symptoms, including pain or discomfort in the abdomen and changes in bowel movement patterns. Studies estimate that IBS affects 10 to 15 per cent of adults in the United States. IBS-D is a subtype characterized mainly by loose or watery stools at least 25 percent of the time.

“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., director of the Office of Drug Evaluation III in FDA’s Center 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, which contains a new active ingredient, is taken orally twice daily with food. Viberzi activates receptors in the nervous system that can lessen bowel contractions. Viberzi is intended to treat adults with IBS-D.

Xifaxan can be taken orally three times a day for 14 days, for the treatment of abdominal pain and diarrhoea in patients with IBS-D. Patients who experience a recurrence of symptoms can be retreated with a 14 day treatment course, up to two times. Xifaxan, an antibiotic derived from rifampin, was previously approved as treatment for travellers’ diarrhoea caused by E. coli and for reduction of the risk in adult patients of recurring overt hepatic encephalopathy, the changes in brain function that occur when the liver is unable to remove toxins from the blood. The exact mechanism of action of Xifaxan for treatment of IBS-D is not known, but is thought to be related to changes in the bacterial content in the gastrointestinal tract.

The safety and effectiveness of Viberzi for treatment of IBS-D were established in two double-blind, placebo-controlled clinical trials in which 2,425 patients were randomly assigned to receive Viberzi or placebo. Results showed Viberzi was more effective in simultaneously reducing abdominal pain and improving stool consistency than placebo over 26 weeks of treatment.

The safety and effectiveness of Xifaxan for treatment of IBS-D were established in three double-blind, placebo-controlled trials. In the first two trials, 1,258 patients were randomly assigned to receive Xifaxan or placebo for 14 days, and then followed for a 10-week treatment-free period. More Xifaxan-treated patients reported improvements in abdominal pain and stool consistency than those on placebo. A third trial evaluated repeat courses of Xifaxan, because patients with IBS-D can develop recurrent signs and symptoms after a single treatment course of Xifaxan. A total of 636 patients with recurrence were randomized to receive either Xifaxan or placebo for two additional 14-day courses separated by 10 weeks. More patients treated with Xifaxan than placebo were responders in abdominal pain and stool consistency in this phase of the study.

The most common side effects in patients treated with Viberzi include constipation, nausea and abdominal pain. The most serious known risk associated with Viberzi is the risk of spasm in the sphincter of Oddi, the smooth muscle that surrounds the end portion of the common bile and pancreatic ducts, which can result in pancreatitis. Viberzi should not be used in patients with a history of bile duct obstruction, pancreatitis, severe liver impairment, or severe constipation, and in patients who drink more than three alcoholic beverages per day.

The most common side effects in patients treated with Xifaxan for IBS-D include nausea and an increase in alanine aminotransferase (ALT), a liver enzyme measured in blood. If diarrhoea does not improve or worsens after treatment with Xifaxan, then evaluation for development of a severe infectious diarrhoea, C. difficile enterocolitis, should be performed. Caution should be used when using Xifaxan in patients with severe liver impairment or when combined with certain other drugs.

Viberzi is manufactured by Patheon Pharmaceuticals, Inc. based in Cincinnati, Ohio and distributed by Forest Pharmaceuticals, Inc. a subsidiary of Forest Laboratories, LLC, based in Cincinnati, Ohio.

Xifaxan is marketed by Salix Pharmaceuticals, Inc. based in Raleigh, North Carolina.