Antibiotics, probiotics are options for IBS treatment

NEW ORLEANS — Both probiotics and antibiotics are legitimate, evidence-based treatments for irritable bowel syndrome.

The gut flora of patients with irritable bowel syndrome (IBS) differs quantitatively from that of unaffected individuals. The proposed mechanism of the demonstrated benefit for probiotics and antibiotics lies in the controversial notion that bacterial overgrowth in the small intestines may account for some cases for IBS.

“The thought is that if you can restore a balanced intestinal flora in somebody with IBS, you may be able to eliminate the symptoms,” a gastroenterologist at Walter Reed National Military Medical Center in Bethesda, Md. said.

The best-studied probiotic in the treatment of IBS is Bifidobacterium infantis. It is supported by “very powerful” data showing reductions in bloating, abdominal pain, and passing of gas, as well as easing of bowel movement difficulty and normalization of aberrant peripheral cytokine levels.

The effective dose, demonstrated in a 362-patient, multi-center, randomized trial. Bifidobacterium infantis is commercially available as a nutritional supplement in fortified yogurt or in capsule form. Long-term efficacy data are lacking, but the probiotic is devoid of significant side effects.

A meta-analysis showed that oral rifaximin (Xifaxan) provides significant short-term relief of bloating and improved global quality of life scores in patients with IBS. In this study of five randomized, placebo-controlled clinical trials with a total of 1,803 patients, the number needed to treat was roughly 10 for both outcomes. The outcomes were better in older female patients.

The researchers characterized the 10% therapeutic gain over placebo as “modest” and similar to that provided by other accepted therapies for IBS. The longest study of rifaximin followed patients for only 12 weeks. “I would caution you in using antibiotics for a benign, incurable condition in general. This is a relatively new agent, and we don’t know what the long-term effect is going to be.”