CHICAGO – Norfloxacin therapy relieved symptoms of irritable bowel syndrome better than placebo did in a prospective study of 80 patients, especially in patients with small intestinal bacterial overgrowth.*
The double-blind study randomized 15 patients with small intestinal bacterial overgrowth and 65 patients without overgrowth to treatment with either norfloxacin 400 mg b.i.d. or placebo for 10 days. Small intestinal bacterial overgrowth was diagnosed by a quantitative upper gut aspirate culture showing a total bacterial count of at least 105/mL colony-forming units (CFU) of upper gut aspirate, or a glucose hydrogen breath test showing a rise in breath hydrogen of at least 12 ppm after glucose ingestion.
One month later, irritable bowel syndrome (IBS) symptoms resolved in 15 of 40 patients who received the fluoroquinolone antibiotic (38%) and in none of the 40 patients who got placebo, Dr. Uday C. Ghoshal and his associates reported at the annual Digestive Disease Week. Symptoms were assessed using the Rome III criteria.
Among the 15 patients with small intestinal bacterial overgrowth, symptoms resolved in 7 of 8 who received norfloxacin (88%) and in 0 of 7 who got placebo, reported Dr. Ghoshal of the Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India.
Among the 65 patients who tested negative for small intestinal bacterial overgrowth, symptoms resolved in 8 of 32 who got norfloxacin (25%) and in none of 33 patients on placebo. There was a trend for greater effectiveness with norfloxacin in the 19 patients with moderate colony counts (lower than 105 CFO but at least 103 CFU/mL), with symptoms resolving in 5 of 11 who got norfloxacin (46%) and in none of 8 patients on placebo, but the difference between treatment groups was not statistically significant. Among the 46 patients with the lowest colony counts (below 103 CFU/mL), symptoms resolved in 3 of 21 who got norfloxacin (14%) and in none of 25 on placebo, which was statistically significant.
Mean symptoms scores before treatment in the norfloxacin group were 6 in those with small intestinal bacterial overgrowth, 10 in those without the overgrowth but with moderate colonization, and 8 in those with the least colonization, and decreased significantly in each subgroup 1 month after treatment to 2, 5, and 5, respectively. Among patients on placebo, mean symptom scores before treatment were 10 in those with small intestinal bacterial overgrowth, 6 in those with moderate colonization, and 9 in those with the least colonization and did not change significantly by 1 month after treatment, increasing to 11 in the overgrowth group and remaining at 6 and 9 in the other subgroups.
Repeat cultures and/or glucose hydrogen breath tests 1 month after treatment in 15 patients who consented to retesting suggested that norfloxacin was more effective than placebo was in eradicating small bacterial intestinal bacterial overgrowth, with eradication in 4 of 8 patients on the drug and none of 7 patients on placebo, Dr. Ghoshal said.
Patients were excluded from the study if they had taken antibiotics or probiotics within 8 weeks of the trial or if they had diabetes, thyroid disease, or previous abdominal surgery.
Dr. Ghoshal reported having no financial disclosures.
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Correction, 6/6/14: An earlier version of this article made multiple incorrect references to inflammatory bowel syndrome instead of irritable bowel syndrome.