The purpose of this research study is to determine how Lubiprostone, a medication used to
treat irritable bowel syndrome with constipation predominant symptoms (IBS-C), works to
reduce clinical pain. Lubiprostone acts in the small intestine to cause an increase in the
secretion of chloride, water and sodium. The increased fluid causes food residue to move
through the bowel more quickly and makes the stools softer. First, we want to test the idea
that Lubiprostone works by making a person less sensitive to pain. Second, we want to confirm
that Lubiprostone decreases the time it takes fecal matter to travel through your GI tract,
referred to as transit time.