Chloride channels are proteins that control cell membrane transport of chloride ions and hence modulate intestinal fluid secretion. Chloride channel openers, are currently under development for the treatment of patients with constipation, IBS-C, and postoperative ileus. By activating the specific chloride channel CIC2 in cells lining the gut, lubiprostone increases intestinal fluid secretion, which softens the stool, promotes bowel movement, and thus indirectly decreases abdominal discomfort and bloating. To date, two phase III trials of lubiprostone in patients with constipation showed that, relative to placebo, treatment with lubiprostone significantly improved symptoms of constipation, including stool frequency, stool consistency, and straining. The main adverse events were nausea, diarrhea, and headache.