What is the role of antibiotics in IBS?
The rationale for use of antibiotics in IBS is based on their ability to alter the intestinal microbiota. Alterations in the intestinal microbiota in IBS are supported from multiple lines of evidence. To date, most of the data on the treatment of IBS with antibiotics has been with neomycin and rifaximin.
Although neomycin has been shown to improve IBS symptoms, it has the potential to cause adverse reactions, including ototoxicity, nephrotoxicity, and neuromuscular blockade and respiratory paralysis, especially when given soon after anesthesia or muscle relaxants. Therefore neomycin should be used cautiously for the treatment of IBS.
Rifaximin is a minimally absorbed oral antibiotic with a broad spectrum of activity and a favorable tolerability profile. During the first 4 weeks after treatment with 2 weeks of rifaximin 550 mg three times daily, a greater percentage of rifaximin-treated IBS-D patients reported adequate relief of their global IBS symptoms (40.7% vs. 31.7%, P < 0.001) and IBS-related bloating (40.2% vs. 30.3%, P < 0.001) compared with placebo-treated patients.
Patients receiving rifaximin continue to report improvement in global symptoms after the treatment period as compared with placebo, although its efficacy declines over time. Although not contraindicated in IBS-C, rifaximin has not been well studied in this subgroup of IBS.