Based on the theory that there could be an overgrowth of bacteria in the small intestine (SBO) in patients with IBS, antibiotics have been tried as a treatment. Antibiotics have helped some IBS sufferers, especially those with complaints of diarrhea, excessive bloating, and gas and abdominal pain.
Without well-designed scientific studies showing clear efficacy, the use of antibiotics has been somewhat empirical, and the questions have remained which antibiotic, for how long, and how often? Furthermore, the role of SBO has been exaggerated in the past, with an estimate of only 5-10% of IBS patients having confirmed bacterial overgrowth. However, more recently, the role of post-infectious IBS and altered gut flora in IBS, as well as the availability of unabsorbed antibiotics such as rifaximin and high-quality probiotics such as VSL # 3, has led to increased interest in therapy. with antibiotics and probiotics.
Two recent multicenter, randomized, double-blind, placebo-controlled trials, TARGET 1 and TARGET 2, involving more than 1,000 patients given rifaximin or placebo, have shown favorable, but not “dramatic,” results. The rifaximin dose was 550 mg 2-3 times a day versus placebo, for two weeks followed by a further 10 weeks of follow-up. Constipated patients with IBS were excluded. Bloating and a global assessment of IBS symptoms using a standardized scale were the primary endpoints, while abdominal pain and stool frequency were the secondary endpoints.
Abdominal pain, bloating, and stool symptoms improved after rifaximin treatment. When the data from both studies were combined, it was observed that 41% of those who received rifaximin versus 32% of the placebo group (typical 30% placebo response rate in most treatment studies). Although this reached statistical significance, it is not a great response rate, significantly less than 50% noticing the response. A statistically significant improvement was observed over the three-month study period.
The limitations of the study from my position are that the markers of leaky gut and the serology of IBD were not verified nor were staining for mast cells performed in these patients. The patients also did not receive probiotics.
One of the main advantages of rifaximin is that it is not absorbed from the gastrointestinal tract, so there are no systemic side effects. It also tends to be quick if it works and has been documented to last up to three months. The downside is that it’s expensive, often not covered by insurance, and doesn’t work for more than half of those who try it. Adding a probiotic can help, although there are limited studies to support this as a formal recommendation. A theoretical disadvantage is the possible selection of more resistant bacteria in the intestine.
It’s a regimen that may be worth trying if your insurance covers the antibiotic. I would recommend that celiac disease, inflammatory bowel disease (ulcerative colitis and Crohn’s disease), and microscopic colitis (lymphocytic colitis, collagenous colitis, and mastocytic enterocolitis) be excluded by blood tests and endoscopies with biopsies.