Lubiprostone in Patients With Multiple Sclerosis Associated Constipation

Inclusion Criteria: * Multiple Sclerosis * Chronic Constipation defined as \< 3 spontaneous bowel movements per week by history and confirmed by diary during the 14 day washout period. * Women of child-bearing potential must agree to use adequate birth control. Exclusion Criteria: * history of other clinically significant medical or psychiatric disorders or suicidal ideation. * Subjects who have a suspicion of a mechanical bowel obstruction by clinical evaluation prior to dosing that include nausea, vomiting, abdominal pain or distention. * Subjects with a positive urine pregnancy test prior to dosing. * Medication changes within one month prior to visit one. * Corticosteroid use within 2 months prior to visit one. * Age\<18. * Known intolerance to lubiprostone. * Inability to perform any required study procedures.