New drugs in the management of the irritable bowel syndrome

Irritable bowel syndrome (IBS) continues to provide a major therapeutic challenge to clinicians and those involved in drug development. It seems unlikely from the data before us that this multisymptom syndrome with peripheral and central components is likely to respond reliably in all patients to the same single agent. There is still a lack of well designed, appropriately powered, randomised clinical trials and the problems of dealing with the high placebo response rate in this group of patients remains a dilemma for trial designers. There are, however, some new ideas, particularly those relating to the role of hyperalgesia in IBS, For many patients, abdominal pain and bloating are the most distressing symptoms of this disease and the new drugs targeted at pain control, such as kappa agonists and serotonin antagonists (5-HT3 and possibly 5-HT4), may eventually find a place in the clinical management of this syndrome. Other candidates include somatostatin analogues and antidepressants, the latter predominantly for their effects on increasing pain threshold. More speculative new drugs for IBS include cholecystokinin antagonists such as loxiglumide and the gonadotrophin-releasing hormone analogue, leuprorelin (leuprolide). The results of ongoing randomised clinical trials are still awaited for some of these newer agents.