According to Cedars-Sinai gastroenterologist Mark Pimentel, a growing body of evidence implicates bacterial overgrowth in the small bowel as a cause of gastrointestinal problems such as diarrhea, constipation, bloating and abdominal pain. Although most antibiotics are effective, the American College of Gastroenterologists specifically recommends non-absorbable antibiotics because they work at lower doses, don't contribute to antibiotic resistance and avoid the side effects of systemic drugs.
Neomycin
Neomycin is a non-absorbable antibiotic many patients recognize from over-the-counter topical preparations used to prevent skin infections. Although inexpensive and widely available, a 2003 clinical trial published in the "American Journal of Gastroenterology" found that gastrointestinal symptoms and results from hydrogen breath tests, a key marker of small bowel bacterial overgrowth, improved in less than 30 percent of patients treated with neomycin. In addition, many of the patients for whom neomycin was initially effective later relapsed and re-treatment with neomycin produced no improvements.
Rifaximin
Rifaximin is a synthetic derivative of a family of antibiotics known as rifamycins. Unlike earlier generations of rifamycins, scientists engineered rifaximin to be insoluble in water, thus cells in the gastrointestinal tract cannot absorb it. A 2010 clinical trial published in the journal "Gastroenterology" found that rifaximin improved constipation, diarrhea and abdominal pain in 70 percent of treated patients. Unlike neomycin, most patients who take rifaximin experience sustained relief, and among those who require re-treatment, rifaximin does not lose effectiveness with repeated use. Unfortunately, rifaximin only earned approval from the Food and Drug Administration in 2004, so patients can only buy it as the pricey brand name product, Xifaxan.
Erythromycin
Erythromycin is a systemic antibiotic; however, doctors usually prescribe other drugs over erythromycin because erythromycin frequently causes gastrointestinal side effects, such as diarrhea. In patients with constipation-predominant IBS, Pimentel reports that noctural erythromycin used after an initial course of neomycin or rifaximin seems to produces sustained improvement or even relief from gastrointestinal symptoms, superior to results obtained with neomycin or rifaximin alone. After a six month course of erythromycin, many patients can discontinue treatment altogether without suffering a recurrence. In addition, like neomycin, erythromycin is available as an inexpensive generic drug.
References
- "American Journal of Gastroenterology;" An Evidence-Based Treatment Algorithm for IBS; M. Pimentel; 2010
- American College of Gastroenterology: Understanding IBS
- American College of Gastroenterology: An Evidence-Based Systematic Review on the Treatment of Irritable Bowel Syndrome
- "American Journal of Gastroenterology;" Normalization of Lactulose Breath Testing Correlates with Symptom Improvement; M. Pimentel et al.
- "Gastroenterology;" Rifaximin Treatment for Two Weeks Provides Sustained Relief: M. Pimentel et al.; 2010
