A preparation of the gut-selective, broad-spectrum antibiotic rifaximin has been denied approval for the proposed indication of treatment of non-constipation irritable bowel syndrome (IBS) and IBS-related bloating.

Salix Pharmaceuticals, Inc., which markets the Xifaxan brand of rifaximin in North America, announced in February that it expected the FDA to turn down the supplemental New Drug Application for Xifaxan 550-mg tablets after what the manufacturer described as “a newly expressed need for retreatment information.” The FDA confirmed this in a March 7 letter to Salix.

Xifaxan 550-mg tablets are currently approved to reduce the risk of overt hepatic encephalopathy recurrence in persons aged 18 years and older. The 200-mg tablets are approved for the treatment of traveler’s diarrhea caused by noninvasive Escherichia coli.

Last month, Clinical Advisor reported Salix-sponsored research results showing that Xifaxan relieved IBS symptoms even after the completion of therapy.