Rifaximin on Visceral Hypersensitivity

Irritable bowel syndrome (IBS) is one of the most common gastrointestinal disorders, with a global prevalence of 11% according to a recent meta-analysis. The total cost of managing IBS in the United States is in excess of $30 billion per year, including indirect costs relating to loss of productivity of more than $20 billion. Abdominal pain/discomfort (i.e. visceral hypersensitivity) is present in all patients with IBS and remains the most therapy-resistant symptom. Apart from abdominal pain, which is measured subjectively using visual scales, several studies have shown a significant increase in rectal sensitivity, which is measured objectively using an inflatable balloon. Drugs which are shown to have objective effects on visceral hypersensitivity are crucial in the management of IBS. While certain drugs have shown to decrease abdominal pain, there is very little data to substantiate objective changes in visceral hypersensitivity. Rifaximin is a poorly absorbed antibiotic and the exact underlying mechanism of action for rifaximin in reducing the pain component of IBS remains unknown. However, rifaximin has been shown in randomized controlled trials to decrease abdominal discomfort in all subtypes of IBS. The investigators hypothesize that rifaximin is effective in decreasing rectal visceral hypersensitivity in IBS patients. In this study, the investigators propose to test this hypothesis by measuring visceral hypersensitivity using the graded balloon distention test, before and after a course of rifaximin. To test whether this effect is accompanied by treating SIBO, the investigators will also perform lactulose breath tests before and after rifaximin therapy.