Eluxadoline Bile Acid Malabsorption (BAM) Study

Inclusion Criteria: * Adult men or women aged 18 to 75 years inclusive with a diagnosis of IBS-D per Rome IV criteria. * Participants with evidence of BAM must have a fasting serum 7a-hydroxy-4-cholesten-3-one (7αC4) level ≥ 52.5 ng/mL or total fecal bile acid (BA) \> 2337 micromoles/48 hours (positive result) at screening or within 1 calendar year prior to screening. * Participants without BAM must have a fasting serum 7αC4 level ≤ 47.1 ng/mL or total fecal BA \< 2200 micromoles/48 hours (negative result) at screening or within 1 calendar year prior to screening. * Has an average daily Bristol Stool Form Scale (BSFS) score ≥ 5.0 or ≥ 25% of diary entry days with a BSFS score of 6 or 7 during the 14 days prior to Day 1. * Women of childbearing potential must use hormonal or double barrier contraception or maintain a monogamous relationship with a vasectomized male partner from the date of informed consent until 24 hours after final dose of study drug. * Completed the electronic diary (eDiary) on ≥ 10 of the 14 days prior to Day 1. * Has not used loperamide rescue medication on \> 3 of the 14 days prior to Day 1. Exclusion Criteria: * Has a diagnosis of IBS with a subtype of irritable bowel syndrome with constipation (IBS-C), mixed IBS, or unsubtyped IBS per Rome IV criteria. * Does not have a gallbladder. * Has known or suspected biliary duct obstruction, or sphincter of Oddi disease or dysfunction. (Participants with a history of gallstones may be enrolled). * Has a histo…