Lubiprostone--a novel treatment for irritable bowel syndrome with constipation.

Irritable bowel syndrome (IBS) is a chronic, highly prevalent gastrointestinal motility disorder characterized by abdominal discomfort/pain associated with altered bowel habits such as diarrhea or constipation or both. Current therapy for the constipation-predominant form (IBS-C) comprises fiber or osmotic or stimulant laxatives. However, these may exacerbate the condition or cause electrolyte disturbances. Lubiprostone is a novel selective chloride channel-2 activator that increases fluid secretion in the intestinal apical cell membrane, increasing gut motility and frequency of stool passage, and alleviating abdominal discomfort/pain. Lubiprostone has very low systemic bioavailability and cannot be quantitated in blood, but its active metabolite, M3, has been pharmacokinetically profiled. Lubiprostone reaches peak plasma concentrations within approximately 1 h and has a half-life of 0.9-1.4 h. Despite this short half-life, lubiprostone can be administered orally twice daily. Its efficacy in IBS-C has been demonstrated in two phase III studies; spontaneous bowel movement frequency increased and stool consistency improved, whereas straining, bloating and severity of constipation decreased. The beneficial effects continued for up to 4 weeks after cessation of lubiprostone. Lubiprostone was well tolerated in the long-term, with nausea and diarrhea being the commonest adverse events. Further studies are ongoing in opioid-induced bowel dysfunction.