Lack of recruitment

Delayed colonic transient time secondary to a multi-degenerative process is the most likely cause of constipation in idiopathic PD. Since lubiprostone demonstrated its ability to accelerate colonic transit time in healthy volunteers in addition to activating the chloride channels in the intestinal cells, it has the potential to improve constipation in patients with PD with no subsequent adverse events on the control of the neurological manifestation of PD. So we hypothesize the following:

1. Lubiprostone will improve ratings on the Bristol stool form scale (BSFS) in patients with PD induced constipation compared to baseline.(primary)
2. Lubiprostone will increase the number of spontaneous bowel movements (SBM) per week, compared to baseline. (secondary)
3. Lubiprostone will improve health related quality of life in subjects with PD induced constipation. ( secondary)

Inclusion Criteria:

1. Age 50-85 years
2. Diagnosis of Parkinson's disease
3. Constipation as defined by the Rome III committee
4. BSFS of more or equal to 1 and less or equal to 3
5. Normal colonoscopy in the last 5 years( normal defined as absence of obstructive lesions in the colon)
6. All women subjects will be post menopausal or surgically sterile.

Exclusion Criteria:

1. Known hypersensitivity reaction to Amitiza ( Lubiprostone)
2. Known significant adverse effects to previous treatment with Lubiprostone which include; new or worsening abdominal pain, severe diarrhea, nausea, vomiting, and severe headache.
3. Renal dysfunction with creatinine clearance less than 15 ml/min
4. Abnormal liver enzymes or history of chronic liver disorder
5. History of bowel obstruction, , or abdominal adhesions .
6. Abnormal Colonoscopy ( obstructive lesions within the colon)
7. Inability to give informed consent

up to 6 weeks

Early termination leading to small numbers of subjects analyzed