ABSTRACT - 598671 The disclosure relates to use of rifaximin in the manufacture of a medicament for treating diarrhea-predominant Irritable Bowel Syndrome (IBS) or alternating- predominant IBS (a-IBS) in a subject 65 years old or older in need thereof, wherein the medicament is formulated for administration of 550 mg of rifaximin three times a day (TID) to the subject, for between about 14 days and about 24 months.
