Clinical Trial: Rifaximin Versus Low FODMAP Diet in Irritable Bowel Syndrome

Background Rifaximin and the low FODMAP diet (LFD) are suggested as second‐line therapies for irritable bowel syndrome (IBS). Direct comparative data are limited. Aims To compare the efficacy of rifaximin and LFD in IBS. Methods In this single‐blind, randomised controlled trial, we allocated adults with IBS to rifaximin or LFD. The primary outcome was composite symptom improvement (abdominal pain/discomfort and stool consistency/frequency) at Week 4. Secondary outcomes included individual symptom improvement, ≥ 50 point reduction in IBS Symptom Severity Scale (IBS‐SSS), health‐related quality of life (HRQOL), Hospital Anxiety and Depression Scale (HADS), small intestinal bacterial overgrowth (SIBO) eradication, adherence and adverse events. Results We randomised 100 patients equally (median age 50 years; 52% female; 68% IBS‐D; 17% SIBO). Based on the composite symptom assessment, response rates were similar between groups (rifaximin 56.0% vs. LFD 48.0%, p = 0.423) at Week 4. However, rifaximin led to significantly earlier individual symptom improvement at Week 2, including global symptoms (90.0% vs. 72.0%, p = 0.022), bloating (84.0% vs. 58.0%, p = 0.004) and abdominal pain (80.0% vs. 58.0%, p = 0.017). HRQOL and anxiety scores improved in both groups. SIBO eradication was observed in 63.6% (rifaximin) and 50.0% (LFD). Adherence was significantly better with rifaximin (95.9% vs. 77.8%, p = 0.008). No serious adverse events occurred. Conclusion Rifaximin is as effective as LFD in treating IBS over 4 weeks. However, it provides faster symptom relief and higher treatment adherence, making it a practical alternative for symptom management. Trial Registration ClinicalTrials.gov: NCT number: NCT04841980