Research at Cedars-Sinai have found that Xifaxin (rifaximin) may be an effective long-term treatment for irritable bowel syndrome (IBS). Participants benefited from the antibiotic use even after the course of treatment ended, supporting previously published research identifying small intestine bacterial overgrowth (SIBO) as a possible cause of the disease. Among study subjects whose primary symptom was diarrhea, those on the antibiotic showed more than twice the improvement of those on the placebo (49 percent vs. 23 percent). Patients received the drug (or placebo) for 10 days and were then followed for a total of 10 weeks. Participants kept a stool diary, took a questionnaire and were given methane breath tests. The positive effects of the drug were shown to continue throughout most of the 10-week study, not just during the actual antibiotic course. In 2000, Pimentel linked bloating, the most common symptom of IBS, to bacterial fermentation, showing that small intestine bacteria overgrowth (SIBO) may be the causative factor in IBS (The American Journal of Gastroenterology, Dec. 2000). In the first study, an abnormal breath methane profile was shown to be 100 percent predictive of constipation-predominant IBS. In the current study, the correlation between the amount of methane and the amount of constipation was confirmed, another key finding.