Irritable Bowel Syndrome (IBS) is a common disorder, defined by symptom-based diagnostic criteria. The pathogenesis is multifactorial and gut motor dysfunction is considered to be a contributing factor. Changes in motor patterns in the small bowel in IBS patients are quantitative rather than qualitative with no distinct patterns to distinguish patients from healthy individuals. Changes in motor patterns can affect transit of bowel contents. Indeed, variation in intestinal transit was reported in patients with IBS.

Lubiprostone is a novel agent that is Food and Drug Administration (FDA) approved for the treatment of chronic constipation. More recently 2 randomized double-blind, placebo-controlled trials showed the drug to be effective in relieving symptoms in patients with constipation-predominant Irritable Bowel Syndrome (C-IBS), resulting in approval for female patients with C-IBS at a dose of 8 micrograms twice a day.

The investigators hypothesize that lubiprostone works not just as a laxative, but by actually altering motility patterns in the small intestine of female patients with C-IBS. These alterations can be measured through High Resolution Manometry (HRM), a new technique that uses catheters with multiple closely spaced sensors and special software that uses color schemes to portray a pressure gradient. This technique allows a detailed assessment of the direction and spread of contractions. The investigators would like to use HRM to see if lubiprostone affects intestinal contractions by giving blinded participants lubiprostone and placebo while they are undergoing High Resolution Manometry and seeing if any changes in contractions occur. Participants will be recruited from investigator's clinic. If interested, potential subjects will be provided with a copy of the consent form for review. Patients will be informed that after they have had an opportunity to review the consent form, they may contact the study team to further discuss the research and address any questions/concerns they have.

Participants will undergo a screening visit and a manometry visit. During the screening visit investigators will determine eligibility, including application of inclusion/exclusion criteria and administration of a pregnancy test. Then during the manometry visit patients will receive two capsules, lubiprostone and placebo, three hours apart during HRM. Patients will receive each capsule only once and will not know which order they're receiving them in.

Irritable Bowel Syndrome (IBS) is a common disorder, defined by symptom-based diagnostic criteria. The pathogenesis is multifactorial, and gut motor dysfunction is considered to be a contributing factor. Dysmotility affects both the small bowel and the colon. Changes in motor patterns in the small bowel in IBS are quantitative rather than qualitative, with no distinct patterns to distinguish patients from healthy individuals. Changes in motor patterns can potentially affect transit of bowel contents and contribute to symptoms. Indeed, variation in intestinal transit was reported in patients with IBS. Small bowel transit studies, using scintigraphy, radio-opaque markers and hydrogen breath test, have shown that transit is delayed in constipation-predominant Irritable Bowel Syndrome (C-IBS) and accelerated in diarrhea-predominant Irritable Bowel Syndrome (D-IBS).

Lubiprostone is a novel agent that has been Food and Drug Administration (FDA) approved for the treatment of adult males and females with chronic constipation. More recently, 2 randomized, double-blind, placebo-controlled trials showed the drug to be effective in relieving symptoms in patients with C-IBS, resulting in approval for female patients with C-IBS, at a dose of 8 micrograms twice a day.

The investigators hypothesize that lubiprostone works not just as a laxative, but by actually altering motility patterns in the small intestine of female C-IBS patients. These alterations could be measured through High Resolution Manometry (HRM), a new technique that uses catheters with multiple, closely spaced sensors, and special software that uses color schemes to portray a pressure gradient. This technique allows a detailed assessment of the direction and spread of individual contractions.

The investigators would like to use HRM to see if lubiprostone affects intestinal contractions. The investigators would like to achieve this by administering blinded participants lubiprostone and placebo while they are undergoing HRM and seeing if any changes in contractions occur. Participants will be recruited both from the investigator's own clinic and by word of mouth. Patients of the investigators will be approached by a member of the research team during a regularly scheduled clinic visit. If interested, potential subjects will be provided with a copy of the consent form for review. Patients will be given ample time to review the consent form with friends, family, and/or other physicians. Patients will be informed that after they have had an opportunity to review the consent form, they may contact the study team to schedule an appointment with one of the co-investigators to further discuss the research and address any questions or concerns the patient may have. Once all the potential subject's issues and concerns have been addressed, and the individual would like to enroll in the study, an investigator or co-investigator will obtain informed consent. Referring physicians will be asked to give their patients the contact information for the study team and the recruitment process will proceed as described above.

Participants will undergo two visits: a screening visit and a manometry visit. During the screening visit we will determine eligibility, including application of inclusion/exclusion criteria and administration of a pregnancy test. Then during the manometry visit, patients will receive the two capsules (lubiprostone and placebo), three hours apart during HRM. Patients will receive each capsule only once, but they will not know which order they're receiving them in.

Patients may receive lubiprostone without participating in the research study. As lubiprostone is FDA approved, the indications would be the same, however, patients receiving the drug under standard of care would not be undergoing the HRM or receiving a placebo capsule. Patients also may not be required to undergo a washout from their standard medication before starting on lubiprostone.

Inclusion Criteria:

• Constipation predominant IBS (C-IBS) patients diagnosed on the basis of Rome III criteria
• Females 18 years or older with no operations (except for appendectomy) or medical conditions that can affect small bowel motility
• Ability to comply with the requirements of the entire study
• Patient has given written informed consent to participate and is willing to participate in the entire study
• Patients must not be pregnant or nursing as evidenced by a negative serum pregnancy test taken 7-10 days prior to the manometry. Any female with a positive pregnancy test will be immediately discontinued from the study

Exclusion Criteria:

• Evidence of structural abnormality of the gastrointestinal tract or disease/conditions. These conditions include (but are not limited to): current evidence of history of inflammatory bowel disease (Crohn's disease or ulcerative colitis), active diverticulitis, duodenal ulcer, erosive esophagitis, gastric ulcer, gastroparesis, gastrointestinal malignancy, Barrett's esophagus, gastrointestinal obstruction, carcinoid syndrome, pancreatitis, cholelithiasis, amyloidosis, ileus, progressive systemic sclerosis (scleroderma), anorexia nervosa
• Patients with previous gastrointestinal surgery other than appendectomy or cholecystectomy
• Evidence of cathartic colon or a history of laxative use, that in the investigator's opinion is consistent with severe laxative dependence such that the patient is likely to require or use laxatives during the study
• Patients with clinically diagnosed diarrhea defined as 3 stools/day that are loose or watery in nature
• Psychosis, schizophrenia, mania, severe depression or major psychiatric illness needing pharmacological treatment. Well-compensated depression does not exclude a potential patient. Antidepressant medication is allowed if patient has been on a stable dose for at least the past 3 months
• Any evidence or treatment of malignancy (other than localized basal cell, squamous cell skin cancer or in-situ uterine cervix cancer that has been resected) within the previous five years
• Clinical evidence (including physical examination, laboratory tests and Electrocardiogram) of non-controlled cardiovascular, respiratory, renal, hepatic, hematologic, neurologic, psychiatric diseases or any disease that may interfere with the study
• Existence of surgical or medical conditions that might interfere with the absorption, distribution, metabolism and excretion of the study drug (i.e., gastrectomy, severe renal insufficiency)
• Symptoms of a significant clinical illness in the preceding two weeks prior to the Screening Visit
• Use of any concurrent prohibited medications e.g., drugs that affect Gastrointestinal (GI) motility including lubiprostone, antibiotics (erythromycin), prokinetics, narcotic analgesics, calcium channel blockers, nitroglycerin, and antispasmodics. Patients must not have taken prohibited medications at least 7 days prior to manometry.
• Planned use of drugs or agents 7 days prior to the Screening Visit that affect gastrointestinal motility and/or perceptions including erythromycin
• Use of an investigational drug or participation in an investigational study, within 30 days of the Screening Visit
• Known hypersensitivity to the drug.
• Based on investigator opinion, evidence of alcohol or drug abuse within the past two years

Limited time period resulting in recruitment of only 4 patients.