Patients with constipation often have bloating and abdominal distension. It is unclear if this is related to intestinal bacteria. Hypothesis: treatment for constipation may reduce small bowel and colon bacteria colonization, a change in the balance of stool microorganisms, and improve the symptoms of dyspepsia and constipation.

This is an open-label study to collect data on upper and lower GI symptoms, hydrogen breath test, stool PCR, and serum before and after 4 weeks of lubiprostone 24 mcg by mouth twice a day for 4 weeks.

Inclusion Criteria: Functional constipation by Rome III criteria

Exclusion Criteria:

1. History of esophageal or gastric surgery (including vagotomy, antireflux, and obesity surgery)
2. History of small bowel or colon resection (excluding appendectomy and cholecystectomy)
3. History of gastric outlet, small bowel, or colon obstruction
4. History of surgery for small bowel adhesion lysis
5. History of surgery for gastroparesis
6. Diagnosis of diabetes requiring daily medications
7. Diagnosis of connective tissue d/o (including scleroderma, lupus, mixed connective tissue disorder)
8. Diagnosis of neuromuscular disorder (including multiple sclerosis, Parkinson, muscular dystrophy, dysautonomia, dystonia)
9. Disorders of small bowel pseudo-obstruction or dumping syndrome
10. Untreated or poorly controlled hypothyroidism
11. Taking an opiate medication daily
12. Taking a medication daily that can cause constipation (calcium channel blocker, anticholinergic, iron supplements, etc.)
13. Active cancer being treated
14. History of significant liver, kidney, cardiac disease that may interfere with study compliance
15. Known allergy or side effects to lubiprostone
16. Non-ambulatory patients: bed-ridden, nursing home resident, etc.