Provided is a solid dispersion of rifaximin comprising rifaximin and a pharmaceutically acceptable carrier. Preferred pharmaceutically acceptable carriers include urea, sugar, organic acids, polyethylene glycol, povidone, copovidone, polymethacrylates, polyvinyl acetate, cellulose derivatives, self emulsifying carners, poloxamer, glyceryl behenate, polyethyleneglycol derivative of a mono-glyceride, vitamin E, polyethylene or polyoxyethylene ester of hydroxyl stearic acid, polyoxylglycerides, polyethoxylated castor oil, polysorbate 80 and sorbitan or combinations thereof. Further provided are: a pharmaceutical composition comprising the solid dispersion, and uses of the dispersion in the treatment of microbial infection or Crohn&rsquo；s disease or irritable bowel syndrome.
