Rifaximin-treatment for collagenous colitis: A randomised, double-blind, placebo-controlled trial

Introduction: Collagenous colitis (CC) is a disabling disease primarily affecting elderly women. Sparse, well-documented treatment modalities exist, except for budesonide. Long term and repetitive treatment with budesonide is often necessary. Rifaximin is a poorly absorbed antibiotic with a positive modulatory effect on gut microbiota. In this randomised, double-blind, placebo-controlled single center trial, we test the effect of adding rifaximin in continuation to budesonide on relapse rates in collagenous colitis. Methods: Eligible patients with active, biopsy verified CC received oral budesonide during a 6-week open-label induction phase. Patients in clinical remission after four weeks of treatment were randomised to receive either rifaximin or placebo for four weeks. Results: Fifteen patients were randomised to receive either rifaximin (n=7) or placebo (n=8). At 12-week follow-up, two patients in the rifaximin group were still in remission and none in the placebo group (p = 0.2). The median number of days in remission in the rifaximin group was 42 (IQR 33-126) compared to 18.5 (IQR 10.5-51.5) in the placebo group (P = 0.189). At 12-week follow-up the relapse rate per 100 person-days in the placebo group was higher (3.25 (1.40-6.41)) than in the rifaximin group (1.33 (0.43-3.10)). Conclusion: Although not statistically significant (p = 0.0996), the study suggests a potential improvement in relapse rates within the rifaximin group compared to the placebo group. A major limitation in the study is the small sample size.