New Type of Antibiotic Is Nonabsorbable
Irritable bowel syndrome (IBS) af?fects approximately 10% to 20% of the general population and is one of the most common disorders seen by primary care physicians, ac?cording to the International Found?ation for Functional Gastro?intestinal Dis?orders. While the Rome II criteria are the standard diagnostic tool for ?id?entifying IBS, some experts believe that this standard is too strict for pri?mary care practice and, as a result, many patients with IBS remain undiagnosed.
A new double-blind, randomized, placebo-controlled study published in the American Journal of Gastr?enterology (2006;101:326-333) reports that rifaximin (Xifaxan) effectively treats many symptoms of IBS, including ?bloating, a difficult-to-treat problem in these patients.
The study, conducted by Ala I. Sharara, MD, FACP, of the American University of Beirut Medical Center, Lebanon, and colleagues, in?cluded 124 patients with comparable baseline characteristics, none of whom had abnormal results on lactulose H2-breath testing. Of these pa?tients, 63 were randomized to the study drug and 61 to placebo. Treat?ment consisted of 3 ten-day phases: base?line (phase 1), treatment with ri?faximin 400 mg twice daily or placebo (phase 2), and posttreatment (phase 3). Rome II criteria were met in 58.7% of those in the treatment group and 54.1% of those in the placebo group.
Some 41% of those in the treatment group reported feeling im?prove?ment in symptoms of abdominal bloating, ?dis?tension, and flatulence by the end of phase 2 compared with 23% of those in the placebo group (P = .03). Im?prove?ment in symptoms was maintained through the end of phase 3 in 28.6% of those in the treatment group and only 11.5% of those in the placebo group ?(P = .02).
The investigators noted that this is the first study of its kind to focus on the symptoms of bloating, abdominal distension, and flatulence in a community setting regardless of whether patients fit the strict Rome II standards.
"We found that 50% to 60% of these individuals have bona fide IBS, leaving a good number of community subjects suffering from chronic functional gas-related symptoms that would normally be excluded from IBS studies because of adherence to strict diagnostic criteria," the investigators wrote.
They warned about the dangers of long-term antibiotic use, however, citing side effects and the risk of bacterial resistance.
Nevertheless, rifaximin?a rifamycin derivative with broad-spectrum bacterial activities?may be a suitable candidate for long-term use, because it is a semi-synthetic, nonsystemic (ie, nonabsor?b?able) antibiotic, without any known side effects. It received FDA approval in May 2005 for the treatment of traveler's diarrhea caused by Escherichia coli. Additional studies are needed to evaluate long-term use and potential side effects.