Antibiotic treatment effective for most common gastrointestinal disorder in US, research shows

A ground-breaking antibiotic therapy is the first potential drug treatment to provide irritable bowel syndrome patients with long-lasting relief of their symptoms even after they stop taking the medication, according to a study published in the Jan. 6 issue of the New England Journal of Medicine.   

Unlike other traditional therapies for Irritable Bowel Syndrome, patients in these large studies reported relief of their symptoms for up to 10 weeks after completing treatment with rifaximin, says William D Chey, MD, professor in the Department of Internal Medicine at the University of Michigan.   

Rifaximin is a minimally absorbed antibiotic that stays in the gut. Specifically, patients reported improvement in overall IBS symptoms, relief from bloating, less abdominal pain and improved stool consistency for up to 10 weeks, says Chey, one of the researchers on the study and director of the Michigan Bowel Control Program.  

While the concept of bacteria playing a key role in this condition was controversial when first introduced a decade ago, this research confirms that bacteria in the gut, also known as the “gut microbiome", plays a role in the symptoms of IBS, a chronic condition affecting an estimated 30 million people in the United States. The therapy was developed at Cedars-Sinai Medical Center.   

These findings show that targeted antibiotics provide safe and effective long-lasting relief for this condition, says Mark Pimentel, M.D., GI Motility Program director and principal investigator of the clinical trials at Cedars-Sinai.   

“This represents a big change in the way we think about and treat IBS,” says U-M’s Chey, adding that IBS often does not respond well to treatments currently available like dietary changes or fiber supplements alone. Patients also often see a return of symptoms once traditional medical treatments are stopped. But with this new treatment, the patients feel better and continue to feel better after stopping the drug.  

In two, 600-plus patient double-blind trials, IBS patients with mild to moderate diarrhea and bloating were randomly assigned to take a 550 milligram dose of rifaximin or placebo three times daily for two weeks. Study participants were then followed for 10 weeks more. About 40 percent of patients who took the drug reported they had significant relief from bloating, abdominal pain and loose or watery stools. Further, that relief was sustained for weeks after completing treatment with the antibiotic.  

Doctors commonly categorize IBS patients with a “constipation predominant” condition, a “diarrhea-predominant”  condition, or a mixed pattern of diarrhea and constipation. In addition, patients often experience abdominal pain or cramps, excess gas or bloating, and visible abdominal distension.  

Because the cause of the disease had been elusive, treatments for the disease historically have focused on relieving its symptoms with medications that either slow or speed up the digestive process. Earlier research documents a link between bloating, the most common symptom, and bacterial fermentation in the gut related to small intestine bacterial overgrowth, or SIBO. Other research has suggested that the bacteria which reside within the small and large intestines of IBS patients may be different than those inhabiting the intestines of healthy individuals.  

Rifaximin is approved by the US Food and Drug Administration to treat travelers’ diarrhea and hepatic encephalopathy.   

Besides Cedars-Sinai and U-M, other centers participating in the clinical trials included Beth Israel Deaconess Medical Center in Boston, University of North Carolina at Chapel Hill, and Connecticut Gastroenterology Institute in Bristol, Conn.  

Rifaximin is marketed by Salix Pharmaceuticals Inc. Salix also provided funding for the studies. Pimentel discovered the use of rifaximin for IBS, and Cedars-Sinai holds patent rights to this discovery and has licensed rights of the invention to Salix. Dr Pimentel is a consultant to Salix, Inc, and serves on its scientific advisory board.  

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