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FDA Approves Two Therapies for Irritable Bowel Syndrome

Viberzi and Xifaxan get green light

The FDA has approved Viberzi (eluxadoline, Patheon Pharmaceuticals/Forest Pharmaceuticals) and Xifaxan (rifaximin, Salix Pharmaceuticals) for the treatment of irritable bowel syndrome with diarrhea (IBS-D) in adult men and women.

According to the National Institutes of Health, patients with IBS experience a number of signs and symptoms, including pain or discomfort in the abdomen and changes in bowel- movement patterns. Studies have estimated that IBS affects 10% to 15% of adults in the U.S. IBS-D is a subtype characterized mainly by loose or watery stools at least 25% of the time.

Viberzi is taken orally twice daily with food. Its active ingredient, eluxadoline, activates receptors in the nervous system that can lessen bowel contractions. The drug is intended to treat adults with IBS-D.

Xifaxan is taken orally three times a day for 14 days for the treatment of abdominal pain and diarrhea 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’s active ingredient, rifaximin, is an antibiotic derived from rifampin. The drug was previously approved as a treatment for travelers’ diarrhea caused by Escherichia coli and for reducing the risk of recurring overt hepatic encephalopathy in adults. The exact mechanism of action of Xifaxan in the treatment of IBS-D is not known but is thought to be related to changes in the bacterial content of the gastrointestinal tract.

The safety and efficacy of Viberzi for the treatment of adults with IBS-D were established in two double-blind, placebo-controlled clinical trials in which a total of 2,425 patients were randomly assigned to receive eluxadoline or placebo. The results showed that eluxadoline was more effective in simultaneously reducing abdominal pain and improving stool consistency than placebo during 26 weeks of treatment.

The safety and efficacy of Xifaxan for the treatment of IBS-D were established in three double-blind, placebo-controlled trials. In the first two studies, a total of 1,258 patients were randomly assigned to receive rifaximin or placebo for 14 days, and were then followed for a 10-week treatment-free period. More rifaximin-treated patients reported improvements in abdominal pain and stool consistency than did those given placebo.

A third trial evaluated repeat courses of rifaximin because patients with IBS-D can develop recurrent signs and symptoms after a single treatment course of the drug. A total of 636 patients with disease recurrence were randomly assigned to receive either rifaximin or placebo for two additional 14-day courses separated by 10 weeks. More patients treated with rifaximin than with placebo were responders in abdominal pain and stool consistency in this phase of the study.

The most common adverse events in patients treated with Viberzi included 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 adverse events in patients treated with Xifaxan for IBS-D included nausea and increased levels of alanine aminotransferase (ALT), a liver enzyme measured in blood. If the patient’s diarrhea does not improve or worsens after treatment with Xifaxan, then the clinician should perform an evaluation for the development of Clostridium difficile enterocolitis, a severe form of infectious diarrhea. Caution should be used when administering Xifaxan in patients with severe liver impairment or when combined with certain other drugs.

Source: FDA; May 27, 2015.

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