Rifaximin Treatment of Collagenous Colitis: A Randomised, Double-Blind, Placebo-Controlled Trial

<b><i>Introduction:</i></b> 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-centre trial, we test the effect of adding rifaximin in continuation to budesonide on relapse rates in CC. <b><i>Methods:</i></b> Eligible patients with active, biopsy-verified CC received oral budesonide during a 6-week open-label induction phase. Patients in clinical remission after 4 weeks of treatment were randomised to receive either rifaximin or placebo for 4 weeks. <b><i>Results:</i></b> Fifteen patients were randomised to receive either rifaximin (<i>n</i> = 7) or placebo (<i>n</i> = 8). At 12-week follow-up, 2 patients in the rifaximin group were still in remission and none in the placebo group (<i>p</i> = 0.2). The median number of days in remission in the rifaximin group was 42 (interquartile range [IQR] 33–126) compared to 18.5 (IQR 10.5–51.5) in the placebo group (<i>p</i> = 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]). <b><i>Conclusion:</i></b> Although not statistically significant (<i>p</i> = 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.