Small Intestinal Bacterial Overgrowth (SIBO) in Patients With Irritable Bowel Syndrome (IBS); A Retrospective Review of Symptoms Following Treatment

Purpose: IBS has been reported to be associated with SIBO in some patients and antibiotic eradication of SIBO has led to improvement of symptoms in this group of IBS patients. The purpose of this retrospective study was A) to evaluate the efficacy of, the non systemic, gut targeted antibiotic, rifaximin in the treatment and retreatment of patients with SIBO and IBS and B) to determine the significance of the type of gas excreted at initial lactulose breath testing (LBT) in the response to treatment. Methods: Medical charts for all adult patients with SIBO (i.e., positive initial LBT) treated at least once with rifaximin or other antibiotics between December 2005 and December 2008 were reviewed. Patients with IBS and who received rifaximin were included in the analysis. The type of baseline gas excreted during initial LBT and eradication of SIBO (i.e., negative LBT), improvement in the symptoms of IBS, as assessed by physician interview, and the incidence of symptom recurrence after treatment and 1 retreatment were assessed. Concomitant therapies were allowed. Results: A total of 500 charts were reviewed; 153 patients had SIBO and IBS, of which 145 were treated with rifaximin (800, 1200, or 1800 mg/d) for 10, 14, or 30 days. The majority of patients were female (78%), and most patients (74%) excreted hydrogen at baseline LBT. Rifaximin improved symptoms in 85 patients (59%) and eradicated SIBO (negative posttreatment LBT) in 17 patients (12%). A greater percentage of patients (68%) experienced symptom improvement with the highest dose of rifaximin (1800 mg/d) versus those who received 800 mg/d (56%) or 1200 mg/d (55%). Increasing duration of treatment with rifaximin was associated with a greater percentage of patients experiencing symptom improvement. The presence of hydrogen detected by LBT at baseline was significantly associated with SIBO eradication (P=0.03) and IBS symptom improvement (P=0.03) after rifaximin. Symptoms of IBS recurred in 119 patients (82%) after a median of 68.5 days. Of these patients, 42 were retreated with rifaximin (800, 1200, or 1800 mg/d) for 10 to 30 days. After retreatment, symptoms improved in all but 1 patient (98%). Conclusion: In patients with SIBO and IBS, treatment and retreatment with rifaximin improved the symptoms in the majority of patients. Hydrogen eradication may be an indication of favorable response. Disclosure: Infantalino - Salix: research/grant, consultant; Diamond - none; Miller - none; Rupisan - none; DiMarino - Salix: research/grant, consultant. This research was supported by an industry grant from Salix Pharmaceuticals, Inc.