A bicyclic fatty acid derived from prostaglandin E1 and a chloride channel activator with laxative activity. Upon intake, lubiprostone specifically binds to and activates the type 2 chloride channel (ClC-2) in the apical membrane of the gastrointestinal epithelium. This produces an efflux of chloride ions, thereby drawing water into the gastrointestinal lumen. The resulting increased amounts of intestinal fluid soften the stool, increase motility, and improve bowel movements.