Irritable bowl syndrome  is a severe gastrointestinal disorder which is prevalent in the world by 10-20%. It is also known as also known as spastic colitis, nervous colon syndrome. The symptoms include abdominal pain, mucous in stools, bloating and altered bowel function. Although the exact cause is not known, recent studies have shown that gut is involved in irritable bowel syndrome. William D. Chey, M.D., professor in the Department of Internal Medicine at the University of Michigan opined that fibre supplements or changes in diet did not provide permanent relief to the patients as the symptoms returned once these were stopped. About a couple of years ago a pharmaceutical company called Salix introduces a new drug Rifaximin for treating irritable bowel syndrome. But according to FDA more clinical evidence was required to prove the efficacy of the drug.Meanwhile it has been prescribed by doctors in treating irritable bowel syndrome.

The Trial

  • The trial was conducted at Cedars-Sinai Medical Center.
  • Lead author, Mark Pimentel, M.D., GI Motility Program director and principal investigator of the clinical trials at Cedars-Sinai said that antibiotics were safe and efficient in treating this syndrome.
  • The two double blind trials involved 660 patients with mild to moderate  diarrhea and bloating and the drug was administered thrice daily (dosage of 550mg) of rifaximin or a placebo for a duration of a fortnight.Then there was an observation period of ten weeks more.
  • A little less than half of the patients experienced relief from the symptoms like bloating, abdominal pain etc and the the relief continued for weeks even after the antibiotic was stopped.

IBS and SIBO (small intestine bacterial overgrowth)

The symptoms of SIBO are similar to the irritable bowel syndrome. Dr. Mark Pimentel, the Director of the Gastrointestinal motility Program at Cedars-Sinai Medical Center prvided evidence proving that hydrogen breath testing method showed that people with bacterial overgrowth in the intestine led to irritable bowel syndrome symptoms. SIBO can be detected by this test because gut bacteria produce hydrogen during the fermentation of carbohydrates. The Cedars-Sinai Protocol method developed by Dr.Pimentel offers a patients an antibiotic course for ten days after this test. Rifaximin is the most recommended drug in this case and it is approved by FDA for treating traveller’s diarrhea. Neomycin is another antibiotic which is recommended sometimes. Antibiotics like etronidazole, levofloxacin, ciprofloxacin, doxycycline, amoxicillin-clavulanate, trimethoprim-sulfamethoxazole, cephalexin and norfloxacin have been used in treating SIBO and thus it can be speculated that FDA approval can be gained to use antibiotics in treating irritable bowel syndrome.

Merits and demerits of using antibiotics for IBS


The antibiotics like rifaximin and neomycin are contained in the GI tract and have been effective in keeping the symptoms at bay for weeks even after the medicines have been stopped. A large number of people who suffered no cure were relieved after these drugs were administered. The more serious symptoms of SIBO which include steatorrhea, anemia, weight loss, night blindness etc can be prevented.


Studies showed that an antibiotic gave only 10% relief compared toa placebo. Broad spectrum antibiotics kill bacteria indiscriminately, thus it may evoke the symptoms of IBS itself. Long term usage of antibiotics might create resistant strains of bacteria, and might cause allergic reactions.


The effectiveness and safety of the antibiotics in treating IBS is to be further tested through clinical trials. At the initial stage the patients can be helped with proper scientific diet and antibiotics for now should only be used in extreme cases.