Subjects must be 18 years old and older, have diarrhea and microscopic colitis. Pregnant or nursing females are excluded. They can't have other untreated diarrheal conditions. Subjects will receive medication for 8 weeks, followed by sigmoidoscopy with biopsies. The subjects will be monitored weekly. A pathologist will review pre and post treatment biopsies. Subjects that show improvement will be followed for 4 weeks post medication.