Background & aims: No controlled trial has examined the clinical efficacy of antibiotics in small bowel bacterial overgrowth.
Methods: Ten patients with bacterial overgrowth-related diarrhea underwent the following five 7-day treatment periods: untreated (control period), then placebo, and subsequently, in random order and blinded fashion, norfloxacin (800 mg/day), amoxicillin-clavulanic acid (1500 mg/day), and Saccharomyces boulardii (1500 mg/day). A hydrogen breath test was performed on the first and last day of each period.
Results: Daily stool frequency was similar during the control and placebo periods (4.2 +/- 0.6 vs. 3.9 +/- 0.6 [mean +/- SEM], respectively). Norfloxacin and amoxicillin-clavulanic acid led to a significant reduction in daily stool frequency (2.3 +/- 0.4 and 3.0 +/- 0.5, respectively; P < 0.01 vs. placebo period) after 2.0 +/- 1.4 and 1.2 +/- 0.4 days, which was maintained for 6.1 +/- 3.7 and 6.0 +/- 9.6 days, respectively. Breath-expired H(2) volume decreased with norfloxacin (37 +/- 8 to 12 +/- 5 mL per 2 hours; P < 0.01) and amoxicillin-clavulanic acid (24 +/- 6 to 8 +/- 4 mL per 2 hours, respectively; P = 0.01), but H(2) breath test result was negative in only 3 and 5 patients.
Conclusions: Norfloxacin and amoxicillin-clavulanic acid are effective in the treatment of bacterial overgrowth-related diarrhea.