Irritable bowel syndrome (IBS), a complex disorder of the gastrointestinal tract, is characterized by abdominal pain associated with defecation or changes in stool form or frequency. IBS is associated with substantial burden, including direct medical costs and indirect costs. Direct costs associated with IBS in the United States have been estimated to exceed $1 billion. However, indirect costs, such as negative effect on quality of life (QOL) and work productivity, are difficult to quantify. There are 3 main subtypes: IBS with prominent diarrhea (IBS-D), IBS with constipation, and IBS with mixed symptoms of both constipation and diarrhea. A number of pharmacologic agents have been used to treat IBS-D despite lack of approval by the FDA for this indication. The pharmacologic agents that are indicated by the FDA for the treatment of IBS-D include alosetron, eluxadoline, and rifaximin. The negative impact of IBS-D symptoms on QOL reported by patients indicate there is an unmet need for therapies that effectively treat and manage the symptoms of this condition. Addressing gaps in treatment is an important priority.