<prompt> Lubiprostone is a:Chloride channel activatorChloride channel inhibitorSodium channel activatorSodium channel inhibitor  <response>: Lubiprostone :- selectively stimulates type 2 chloride channels in epithelial cells thereby causing an efflux of chloride into the intestinal lumen. - The resultant fluid secretion into the gastrointestinal lumen provides a bolus effect that softens stool, increases intestinal transit, and improves symptoms of constipation. - Lubiprostone acts locally within the intestinal tract, is rapidly metabolized, and has very low systemic bioavailability. 