Efficacy of rifaximin, a nonabsorbed oral antibiotic, in the treatment of small intestinal bacterial overgrowth

Am J Med Sci. 2007 May;333(5):266-70. doi: 10.1097/MAJ.0b013e3180536784.


Introduction: Rifamixin is an orally administrated, nonabsorbed antibiotic whose utility in eradication of small intestinal bacterial overgrowth (SIBO) is currently being evaluated.

Purpose: The aim of this study was to investigate efficacy and safety of rifaximin in relieving symptoms and normalizing the glucose breath test (GBT) in patients with SIBO.

Methods: Symptom score assessment, consisting of frequency and severity of bloating, gas, abdominal pain, and bowel movements and the GBT were performed before and after treatment with rifaximin 800 mg/d for 4 weeks.

Subjects: Twenty consecutive symptomatic patients (16 women and 4 men; mean age, 47.8 years; range, 19 to 85 years) who had a positive GBT were prospectively studied in an open-labeled fashion. Fourteen patients (70.0%) presented with diarrhea, 3 (15.0%) with bloating and gas, and 3 (15.0%) with constipation as the dominant symptom.

Results: : Eleven patients were hydrogen producers, 8 exclusively methane, and 1 patient produced both gases by the GBT. Among patients with diarrhea, 12 of 14 (85.7%) reported improvement in symptom scores of more than 50%; 1 between 25% and 50%, 1 had no response after 4 weeks of rifamixin. Among patients with bloating and gas or constipation as the main symptom: 2 of 6 (33.3%) had improvement between 50% and 75%; 3 (50%) had 25% to 50% improvement, and 1 (16.7%) had no response. Repeat GBT at the end of the 4 weeks showed that 54.5% of hydrogen formers and 50.0% of methane producers were eradicated, and there was a significant reduction (P <0.05) in the area under the concentration-time curve and peak values. No adverse effects were observed.

Conclusions: Rifaximin in a dose of 800 mg per day for 4 weeks: 1) was safe and effective treatment in reducing symptoms in patients with SIBO of multiple etiologies, especially when diarrhea was the dominant symptom; and 2) normalized the GBT in approximately 50% of patients. Data support a future therapeutic role for rifaximin in SIBO.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Anti-Infective Agents / therapeutic use*
  • Bacterial Infections / drug therapy*
  • Breath Tests
  • Female
  • Gastrointestinal Agents / therapeutic use*
  • Gastrointestinal Diseases* / drug therapy
  • Gastrointestinal Diseases* / microbiology
  • Humans
  • Hydrogen / metabolism
  • Intestine, Small / microbiology*
  • Male
  • Methane / metabolism
  • Middle Aged
  • Rifamycins / therapeutic use*
  • Rifaximin
  • Treatment Outcome


  • Anti-Infective Agents
  • Gastrointestinal Agents
  • Rifamycins
  • Hydrogen
  • Rifaximin
  • Methane