Treatments for irritable bowel syndrome

Too many bacteria in the small intestine (small intestinal bacterial overgrowth) is often the cause of irritable bowel syndrome.  One way to test for this is to see if patients have more methane on their breath after they eat some lactulose (lactulose breath test). One study showed that treating irritable bowel syndrome patients with non-absorbable antibiotics resulted in the symptoms going away completely.  This can happen after only 10 days of rifaximin, a non-absorbed oral antibiotic that acts mostly in the small intestine.  Even after patients stopped the antibiotics, they still felt better.  Probiotics have also been used in studies of irritable bowel syndrome with good results.

Othman M, Aguero R, Lin H. Alterations in intestinal microbial flora and human disease (Gastrointestinal infections: edited by Edgar C. Boedeker).