For personal use only 1 of 14 Irritable bowel syndrome: new and emerging treatments Magnus Halland, Yuri A Saito Introduction Irritable bowel syndrome (IBS) is a common gastrointesti- nal disorder characterized by abdominal pain or discom- fort in conjunction with altered bowel habits. Bloating or abdominal distension is also common. IBS remains a symptom based diagnosis because objec- tive tests are currently lacking. The most recent Rome III criteria for a diagnosis of IBS stipulate recurrent abdomi- nal pain or discomfort on at least three days a month in the past three months associated with two or more of the following: improvement with defecation, onset associ- ated with a change in stool frequency, and onset associ- ated with change in stool form (box). 1 IBS can be clinically subtyped into IBS with consti- pation (IBS-C), deined as more than 25% stools being hard or lumpy and less than 25% of stools being loose or watery. Conversely, IBS with diarrhea (IBS-D) is deined as more than 25% of stools being loose or watery and less than 25% of stools being hard or lumpy. Patients who have more than 25% stools being hard and lumpy and more than 25% being loose and watery are diagnosed as having mixed IBS (IBS-M). Epidemiology Global estimates of prevalence vary from 5% to 15%. 2-5 A recent meta-analysis of population based studies conirmed a modest predominance of IBS in women, which varied according to the deinition of IBS (Manning or Rome I, II, or III) used. In all eligible studies (using various IBS deini- tions), the overall odds ratio for IBS in women versus men is 1.67 (95% conidence interval 1.53 to 1.82). 6 The pooled prevalence for women is 14.0% compared with 8.9% in men. Women are more likely than men to seek medical attention for the condition and to report IBS-C, 7 whereas IBS-D is more common in men. 6 The prevalence of IBS decreases with increasing age, and new onset of symptoms ater 50 years is uncommon. 5 IBS clearly afects patients’ quality, but not quantity, of life. 8-11 The inancial impact of IBS for patients, healthcare systems, and society is substantial. 12 For example, a recent review found that the average cost per patient per annum was $742 (£490; €667) to $7547 in the United States, com- pared with £90 to £316 in the United Kingdom and €567 STATE OF THE ART REVIEW Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN 55905, USA Correspondence to: Y A Saito saito.yuri@mayo.edu Cite this as: BMJ 2015;350:h1622 doi: 10.1136/bmj.h1622 ABSTRACT Irritable bowel syndrome is one of the most common gastrointestinal disorders in developed nations. It is characterized by abdominal pain, altered bowel habits, and bloating. Several non-pharmacological and pharmacological agents, which target the peripheral gastrointestinal system and central nervous system, are used to treat the syndrome. The individual and societal impact of investigating and managing the syndrome is substantial, and despite newer treatments, many patients have unmet needs. Intense research at many international sites has improved the understanding of pathophysiology of the syndrome, but developing treatments that are efective, safe, and that have tolerable side efects remains a challenge. This review briefly summarizes the currently available treatments for irritable bowel syndrome then focuses on newer non-pharmacological and pharmacological therapies and recent evidence for older treatments. Recent guidelines on the treatment of irritable bowel syndrome are also discussed. Rome III diagnostic criteria for irritable bowel syndrome (IBS) and subtypes 1 IBS criteria Recurrent abdominal pain or discomfort for at least three days per month in the past three months associated with two or more of the following: • Improvement with defecation • Onset associated with a change in frequency of stool • Onset associated with a change in form (appearance) of stool IBS subtyping by predominant stool pattern • IBS with constipation (IBS-C): – Hard or lumpy stools ≥25% of bowel movements – Loose or watery stools <25% of bowel movements • IBS with diarrhea (IBS-D): – Loose or watery stools ≥25% of bowel movements – Hardy or lumpy stools <25% of bowel movements • Mixed IBS (IBS-M): – Hard or lumpy stools ≥25% of bowel movements – Loose or watery stools ≥25% of bowel movements • Unsubtyped IBS: – Does not meet criteria for IBS-C, IBS-D, or IBS-M