Efficacy of open-label bismuth subsalicylate for the treatment of microscopic colitis

The pathogenesis of the microscopic colitis syndrome is unknown but may involve bacteria, an intestinal luminal antigen, and/or autoimmunity. It was hypothesized that bismuth subsalicylate would resolve both diarrhea and colonic inflammation in microscopic colitis because it possesses antidiarrheal, antibacterial, and anti-inflammatory properties.

Thirteen patients with microscopic colitis (7 with subepithelial collagen deposition and 6 without) were treated with eight chewable 262-mg bismuth subsalicylate tablets per day for 8 weeks. Patients recorded the frequency of bowel movements daily. Forty-eight-hour stool collections and flexible sigmoidoscopy with 24 biopsies were performed before and after treatment in each patient.

Twelve patients completed the trial. Eleven patients had a resolution of diarrhea and a reduction in fecal weight. The average time to respond was 2 weeks. In 9 patients, colitis resolved. When present before treatment, subepithelial collagen thickening disappeared. Those completing the trial experienced no side effects. Posttreatment follow-up for 7-28 months shows that 9 patients remain well having undergone no further treatment, 2 are well but required retreatment, and 1 has continued diarrhea.

Bismuth subsalicylate treatment for 8 weeks is safe and well tolerated. This regimen appears to be efficacious for the treatment of microscopic colitis and is worthy of further study in a controlled trial.