Randomization Scheme: Subjects will be assigned to the Control Group or Lubiprostone Group, on an odd/even basis. After research informed consent has been obtained, subjects are given a study Identification (ID) numbered 1 through 120. Subjects with an odd number will be assigned to Control Group, and subjects with an even number will be assigned to the Lubiprostone Group. Subjects then will be given a randomization package consisting of the preparation orders, supplies, instructions and the date of their procedure by the investigator obtaining informed consent. The colonoscopist will be blinded to which preparation was given.