Antibiotic Fights Intestinal Bacteria, Relieves Irritable Bowel Syndrome
A short course of the antibiotic rifaximin can relieve the symptoms of irritable bowel syndrome for at least 10 weeks in the majority of patients, researchers from Cedars-Sinai Medical Center reported this week in the Annals of Internal Medicine.
The fact that the benefit persisted for so long indicates that “the antibiotic was acting on the source of the problem -- excess bacteria in the gut,” said lead author Dr. Mark Pimentel, director of the Gastrointestinal Motility Program at Cedars.
Irritable bowel syndrome, or IBS, is the most common medical problem in the United States, affecting as much as 20% of the population. Symptoms can include abdominal pain, diarrhea, constipation, bloating, urgency and gas.
Conventional treatments address the symptoms but do little to affect the underlying cause of the disease, which is poorly understood.
Work over the last decade strongly suggests that IBS is caused by an overgrowth of bacteria in the small intestine.
Researchers have attempted to treat IBS with various antibiotics, but they helped only 20% to 40% of patients and have many side effects.
Pimentel decided to test rifaximin, a newer antibiotic, because it kills up to 80% of the 400 bacterial species found in the gut. The drug -- sold for about $200 under the brand name Xifaxan by Salix Pharmaceuticals Inc. -- is not absorbed from the intestine into the rest of the body, which minimizes side effects.
The researchers enrolled 87 IBS patients in the study. Half received rifaximin three times a day for 10 days and half received a placebo.
Those who took the drug had a significant reduction in symptoms that lasted for the 10 weeks of the study, and anecdotal reports indicated that the benefit lasted two to three months, Pimentel said. Patients who got the placebo reported only a small improvement.
The study was funded by Salix. Cedars-Sinai has a patent on the use of rifaximin to treat IBS.
