Treatment of Bacterial Overgrowth in Patients With Irritable Bowel Syndrome

Background: Rifaximin is an effective treatment of irritable bowel syndrome (IBS) with small intestinal bacterial overgrowth (SIBO), yet long-term management has not been well studied. Patients with functional bowel symptoms were characterized by lactulose breath test (LBT), and a comprehensive approach to long-term SIBO therapy was employed. Methods: On day 0, eligible patients completed a baseline symptom questionnaire and were offered rifaximin 1200 mg/d for 10 days followed by tegaserod 3 mg nightly (long-term) plus 1 month of zinc 220 mg/d and a bifidobacteria-based probiotic once daily. Two months later, patients were administered a follow-up questionnaire regarding symptoms at the time of completion of rifaximin therapy and their current symptoms. Results: 161 of 212 patients with an abnormal LBT met Rome II criteria for IBS. High-methane producers were more likely to have constipation. After completion of rifaximin treatment, ≥50% improvement from baseline was reported by 72% of patients for abdominal pain, 67% for flatulence, 62% for bloating, 58% for constipation, 56% for diarrhea, and 53% for fullness. Similar results were reported at 2 months. Global IBS symptoms at 2 months were reported by 60% of patients to be moderately or greatly improved. Moderately or greatly improved symptoms were more frequent among high-methane producers (83%) than high-hydrogen producers (56%) or high producers of both methane and hydrogen (44%). Conclusions: Rifaximin treatment followed by adjunctive therapy was associated with sustained improvement in patients with IBS and SIBO. High-methane producers experienced more frequent constipation and reported greater clinical response compared with high-hydrogen producers.