High Dosage Rifaximin for the Treatment of Small Intestinal Bacterial Overgrowth

E. Scarpellini; M. Gabrielli; C. E. Lauritano; A. Lupascu; G. Merra; G. Cammarota; I. A. Cazzato; G. Gasbarrini; A. Gasbarrini


Aliment Pharmacol Ther. 2007;25(7):781-786. 

In This Article

Summary and Introduction

Background: Rifaximin is a broad spectrum non-absorbable antibiotic used for treatment of small intestinal bacterial overgrowth. Doses of 1200 mg/day showed a decontamination rate of 60% with low side-effects incidence.
Aims: To assess efficacy, safety and tolerability of rifaximin 1600 mg with respect to 1200 mg/day for small intestinal bacterial overgrowth treatment.
Methods: Eighty consecutive small intestinal bacterial overgrowth patients were enrolled. Diagnosis of small intestinal bacterial overgrowth based the clinical history and positivity to H2/CH4 glucose breath test. Patients were randomized in two 7-day treatment groups: rifaximin 1600 mg (group 1); rifaximin 1200 mg (group 2). Glucose breath test was reassessed 1 month after. Compliance and side-effect incidence were also evaluated.
Results: One drop-out was observed in group 1 and two in group 2. Glucose breath test normalization rate was significantly higher in group 1 with respect to group 2 both in intention-to-treat (80% vs. 58%; P < 0.05) and per protocol analysis (82% vs. 61%; P < 0.05). No significant differences in patient compliance and incidence of side effects were found between groups.
Conclusions: Rifaximin 1600 mg/day showed a significantly higher efficacy for small intestinal bacterial overgrowth treatment with respect to 1200 mg with similar compliance and side-effect profile.

Small intestinal bacterial overgrowth (SIBO) is a frequent clinical condition defined as an abnormally high bacterial population level in the upper small intestine, exceeding 106 organisms/mL. SIBO symptoms could be many and variably associated; abdominal pain or discomfort, bloating, diarrohea and/or signs of malabsorption are the most common.[1] Recent findings suggest that SIBO is highly prevalent in patients with irritable bowel syndrome (IBS) and that SIBO decontamination is associated to a significant improvement of IBS symptoms.[2,3]

Glucose (GBT) and lactulose (LBT) breath test have been proposed as simple, inexpensive and non-invasive diagnostic tools for SIBO with respect to the gold standard (the culture of intestinal aspirates).[4,5,6] Specificity and sensitivity of GBT (78-83% and 62-93%, respectively) are acceptable both for screening studies and clinical setting.[4,5,6] Some authors suggested that LBT should be preferred as it may explore SIBO along the entire small bowel.[3] However, it has been criticized by several researchers because of low accuracy (specificity and sensitivity 44-70% and 17-68%).[6,7,8]

Many antibiotics have been proposed in the last years for SIBO eradication. As overgrowth may occur either by a mix of aerobic and anaerobic flora or by purely aerobic flora, an effective antibiotic treatment should act against several bacteria species.[9] Moreover, an ideal regimen should include drugs with low side-effect profile, that is a rare condition with common broad-spectrum absorbable antibiotics proposed for SIBO eradication.[10,11,12]

Rifaximin is a rifamycin derivative with antibacterial activity caused by inhibition of bacterial synthesis of RNA. Rifaximin is effective against both gram-positive and -negative bacteria, including aerobes and anaerobes. As <0.1% of its oral dose is absorbed, rifaximin administration is associated to a very low side-effect incidence.[13,14]

Results from a recent study by our group showed a significantly higher efficacy of a 7 days-1200 mg rifaximin therapy with respect to doses of 600 and 800 mg/die in SIBO treatment (60% vs. 17% and 27%, respectively); side effects were at all the tested dosages rare, mild, transient.[15] Aim of this study is to test the hypothesis that higher rifaximin dosage (1600 mg) with respect to standard dosage (1200 mg) is associated to higher efficacy in SIBO treatment, without changing low side-effects profile.


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