Efficacy and Safety of Oral Rifaximin in Patients With Active Microscopic Colitis

Efficacy and Safety of Oral Rifaximin in Patients With Active Microscopic Colitis

This is an open label study looking at rifaximin therapy for the treatment of microscopic (collagenous or lymphocytic) colitis.

This is an open-label single-arm trial to evaluate the efficacy of Rifaximin in patients with active microscopic colitis (MC). 10 subjects will be asked to take 500mg Rifaximin three times per day for 4 weeks. The primary endpoints will be histologic response and clinical remission (less than 3 stools per day and less than 1 watery stool per day within the prior 7 days. The secondary endpoint will be change of the MC Disease Activity Index (MCDAI).

Inclusion Criteria:

• Collagenous colitis (CC) or lymphocytic colitis (LC) diagnosed on colon biopsies reviewed by 2 separate pathologists
• CC will be defined histologically to be the following: thickness of the collagenous subepithelial table >10 micrometer using an ocular micrometer, inflammation in the lamina propria consisting of mainly lymphocytes and plasma cells, lack of crypt architectural distortion, and regenerative-appearing changes in the surface and/or crypt epithelium
• LC will be defined histologically to be the following: intraepithelial lymphocytes >20 per 100 epithelial cells in the subjective area of highest lymphocyte density, inflammation in the lamina propria consisting of mainly lymphocytes and plasma cells, and regenerative-appearing changes in the surface and/or crypt epithelium
• Subjects in active flare, defined as >3 watery/loose stools per day on >4 / 7 days over >4 weeks in the past 3 months.

Exclusion Criteria:

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