Alosetron controls bowel urgency and provides global symptom improvement in women with diarrhea-predominant irritable bowel syndrome

Randomised, placebo-controlled trial and meta-analysis show benefit of ondansetron for irritable bowel syndrome with diarrhoea: The TRITON trial

BACKGROUND

Ondansetron may be beneficial in irritable bowel syndrome with diarrhoea (IBS-D).

AIM

To conduct a 12-week parallel group, randomised, double-blind, placebo-controlled trial of ondansetron 4 mg o.d. (titrated up to 8 mg t.d.s.) in 400 IBS-D patients.

PRIMARY ENDPOINT

% responders using the Food and Drug Administration (FDA) composite endpoint. Secondary and mechanistic endpoints included stool consistency (Bristol Stool Form Scale) and whole gut transit time (WGTT). After literature review, results were pooled with other placebo-controlled trials in a meta-analysis to estimate relative risks (RR), 95% confidence intervals (CIs) and number needed to treat (NNT).

RESULTS

Eighty patients were randomised. On intention-to-treat analysis, 15/37 (40.5%; 95% CI 24.7%-56.4%) met the primary endpoint on ondansetron versus 12/43 (27.9%; 95% CI 14.5%-41.3%) on placebo (p = 0.19). Ondansetron improved stool consistency compared with placebo (adjusted mean difference - 0.7; 95% CI -1.0 to-0.3, p < 0.001). Ondansetron increased WGTT between baseline and week 12 (mean (SD) difference 3.8 (9.1) hours, versus placebo -2.2 (10.3) hours, p = 0.01). Meta-analysis of 327 patients from this, and two similar trials, demonstrated ondansetron was superior to placebo for the FDA composite endpoint (RR of symptoms not responding = 0.86; 95% CI 0.75-0.98, NNT = 9) and stool response (RR = 0.65; 95% CI 0.52-0.82, NNT = 5), but not abdominal pain response (RR = 0.95; 95% CI 0.74-1.20).

CONCLUSIONS

Although small numbers meant the primary endpoint was not met in this trial, when pooled with other similar trials meta-analysis suggests ondansetron improves stool consistency and reduces days with loose stool and urgency. Trial registration - http://www.isrctn.com/ISRCTN17508514.

Efficacy and safety of vibegron for the treatment of irritable bowel syndrome in women: Results of a randomized, double-blind, placebo-controlled phase 2 trial

BACKGROUND

Preclinical and clinical studies suggest that β₃ -adrenergic receptor activation may be a novel target for treating abdominal pain and gastrointestinal motility dysfunction in patients with irritable bowel syndrome (IBS). This proof-of-concept study evaluated the efficacy and safety of the β₃ -adrenergic agonist vibegron in treating IBS-related pain.

METHODS

Adult women with predominant-diarrhea IBS (IBS-D) or with mixed diarrhea/constipation (IBS-M), diagnosed using Rome IV criteria, were randomized 1:1 to receive once-daily vibegron 75 mg or placebo for 12 weeks. The primary endpoint was the percentage of patients with IBS-D considered abdominal pain intensity (API) weekly responders, defined as ≥30% reduction from baseline at week 12 in mean weekly worst abdominal pain over 24 hours using the API score. Patients completed a pain diary at baseline and at weeks 2, 4, 8, and 12. Safety was assessed by adverse events (AEs) in the overall IBS population.

KEY RESULTS

Of the 222 patients with IBS randomized (vibegron, N = 111; placebo, N = 111), 85% completed the trial. There was no significant difference in the percentage of patients with IBS-D (vibegron, N = 66; placebo, N = 63) considered API weekly responders with vibegron vs. placebo (p = 0.8222) after 12 weeks. The incidence of AEs was comparable between treatment groups (33.3% each), with equal rates of worsening IBS symptoms (2.7% each).

CONCLUSIONS AND INFERENCES

In women with IBS-D, vibegron was not associated with significant improvement in the percentage of API weekly responders. Vibegron was generally safe and well tolerated and, in particular, did not worsen IBS symptoms vs. placebo.

Practical approach to irritable bowel syndrome-diarrhea beyond low-FODMAP diet

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder characterized by abdominal pain and altered defecation, usually accompanied by abdominal bloating or distension. The integrated model of bidirectional interaction between the central, autonomic, enteric nervous system, the microbiome, and the gut barrier allows a better understanding of the pathophysiology of IBS, as well as consideration of potential therapeutic strategies. IBS with predominant diarrhea (IBS-D) represents a therapeutic challenge. Dietary changes or restrictions are most commonly used by patients in an attempt at symptom control. Therefore, a number of diets, especially low-FODMAP diet, have increasingly gained interest as a therapy for IBS-D or mixed IBS. However, this kind of diet, while effective, is not exempt of problems. It is therefore necessary that other therapeutic options be considered while bearing pathophysiological mechanisms and general symptom management in mind.

AGA Clinical Practice Guideline on the Pharmacological Management of Irritable Bowel Syndrome With Diarrhea

BACKGROUND & AIMS

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder associated with significant disease burden. This American Gastroenterological Association Guideline is intended to support practitioners in decisions about the use of medications for the pharmacological management of IBS with predominant diarrhea (IBS-D) and is an update of a prior technical review and guideline.

METHODS

The Grading of Recommendations Assessment, Development and Evaluation framework was used to assess evidence and make recommendations. The technical review panel prioritized clinical questions and outcomes according to their importance for clinicians and patients and conducted an evidence review of the following agents: eluxadoline, rifaximin, alosetron, loperamide, tricyclic antidepressants, selective serotonin reuptake inhibitors, and antispasmodics. The guideline panel reviewed the evidence and used the Evidence-to-Decision Framework to develop recommendations.

CONCLUSIONS

The panel agreed on 8 recommendations for the management of patients with IBS-D. The panel made conditional recommendations for eluxadoline, rifaximin, alosetron, (moderate certainty), loperamide (very low certainty), tricyclic antidepressants, and anstispasmodics (low certainty). The panel made a conditional recommendation against the use of selective serotonin reuptake inhibitors (low certainty).

Adverse events in trials of licensed drugs for irritable bowel syndrome with constipation or diarrhea: Systematic review and meta-analysis

BACKGROUND

Nocebo effects occurring in patients receiving placebo frequently impact on adverse events reported in randomized controlled trials (RCTs) in irritable bowel syndrome (IBS). Therefore, we conducted a systematic review and meta-analysis to assess the proportion of patients randomized to placebo or active drug experiencing any adverse event in trials of licensed drugs for IBS with constipation (IBS-C) or diarrhea (IBS-D), and to estimate the risk of developing adverse events among patients randomized to placebo.

METHODS

We searched MEDLINE, EMBASE CLASSIC and EMBASE, and the Cochrane central register of controlled trials (through June 2021) to identify RCTs comparing licensed drugs with placebo in adults with IBS-C or IBS-D. We generated Forest plots of pooled adverse event rates in both active drug and placebo arms and pooled risk differences (RDs) with 95% confidence intervals (CIs).

KEY RESULTS

There were 21 RCTs of licensed drugs versus placebo in IBS-C (5953 patients placebo) and 17 in IBS-D (3854 patients placebo). Overall, 34.9% and 46.9% of placebo patients in IBS-C and IBS-D trials, respectively, developed at least one adverse event, with a statistically significantly higher risk of any adverse event and withdrawal due to an adverse event with active drug. In IBS-C and IBS-D trials, rates of each individual adverse event were generally higher with active drug. However, in IBS-C trials, only diarrhea or headache was significantly more common with active drug (RD 0.066 (95% CI 0.043-0.088) and RD 0.011 (95% CI 0.002-0.021), respectively), and in IBS-D trials only constipation, nausea, or abdominal pain (RD 0.096 (95% CI 0.054-0.138), 0.014 (95% CI 0.002-0.027), and 0.018 (95% CI 0.002-0.034), respectively).

CONCLUSIONS & INFERENCES

Patients with IBS randomized to placebo have a high risk of reporting adverse events, which might relate to both nocebo and non-nocebo factors. Although patients' expectations and psychosocial factors may be involved, further understanding of the mechanisms are important to control or optimize these effects in RCTs, as well as in clinical practice.

Emerging therapies in the management of Irritable Bowel Syndrome (IBS)

INTRODUCTION

Irritable bowel syndrome (IBS) is a common, symptom-based disorder of chronic abdominal pain and altered bowel habits. The pathogenesis of IBS is multifactorial, leading to the potential for the development of multiple, diverse treatment strategies. This mechanistic heterogeneity also leads to the realization that available therapies are only effective in a subset of IBS suffers. Current US Food and Drug Administration (FDA) approved therapies for IBS with diarrhea (IBS-D) and IBS with constipation (IBS-C) are reviewed. Limited symptom responses and side effect experiences lead to considerable patient dissatisfaction with currently available IBS treatments. Only a small percentage of IBS patients are on prescription therapies underscoring the potential market and need for additional therapeutic options.

AREAS COVERED

: Expanding on currently available therapies, the serotonergic and endogenous opioid receptor systems continue to be a focus of future IBS treatment development. Additional novel emerging therapies include the endogenous cannabinoid system, bile acid secretion and sequestration, and exploit our enhanced understanding of visceral sensory signaling and intestinal secretomotor function.

EXPERT OPINION

While challenges remain for the future development of IBS therapies, the diverse etiologies underlying the disorder present an opportunity for novel therapies. Hence, great potential is anticipated for future IBS treatment options.

Diarrhea-Predominant and Constipation-Predominant Irritable Bowel Syndrome: Current Prescription Drug Treatment Options

Irritable bowel syndrome (IBS) is a heterogenous disease with a variety of therapeutic options, including eight prescription drugs approved for use in IBS in the USA. Choosing among the myriad treatment options requires attention to patient preferences both on clinical outcomes and costs associated with treatment. We performed a narrative review of the literature to summarize these important determinants of treatment choice including: labeled indications; clinical profiles of efficacy, safety, and tolerability of prescription drugs; and cost-effectiveness for diarrhea-predominant IBS drugs (IBS-D: alosetron, eluxadoline, and rifaximin) and constipation-predominant IBS drugs (IBS-C: linaclotide, lubiprostone, plecanatide, tegaserod, and tenapanor). We then review the standard model of shared decision-making aimed at guiding an informed, patient-centered discussion to integrate comparative clinical and cost outcomes toward choosing an IBS treatment in practice.

Medical Therapies for Diarrhea-Predominant Irritable Bowel Syndrome

Diarrhea-predominant irritable bowel syndrome is a common functional gastrointestinal disorder that manifests with abdominal pain and diarrheal bowel patterns, without structural explanation. Diarrhea-predominant irritable bowel syndrome is a heterogeneous condition resulting from diverse pathophysiologic processes. Treatment strategies with varied mechanisms of action are beneficial in its management. The clinician must become familiar with a multi-dimensional approach to irritable bowel syndrome. The 3 approved medications are central to disease management. Effective treatment uses off-label medications and emerging therapies and a growing number of over-the-counter and supplemental agents to optimize symptom improvement for the patient with diarrhea-predominant irritable bowel syndrome.

Assessing the post-treatment therapeutic effect of pinaverium in irritable bowel syndrome: a randomized controlled trial

Irritable bowel syndrome (IBS) is the most common gastrointestinal disorder significantly decreasing patients' lives of quality and placing huge economic burden on our society. Existing studies indicated that the therapeutic effects maintained for a period of time after the treatments were discontinued. It is clinically important to assess these post-treatment therapeutic effects (PTTE), which prevent IBS from relapsing. To assess the PTTE in pinaverium treatment and obtain high-quality evidence to justify the use of PTTE for long-term IBS management, we performed this controlled, double blind study on patients with IBS who were randomized to pinaverium 50 mg (n = 132) or placebo (n = 132), three times daily, for 4 weeks, and were followed up for 57 weeks after the treatments. The primary endpoints were abdominal pain and stool consistency. The secondary endpoints were pain frequency and stool frequency. The tertiary endpoints were global overall symptom and adverse events. Three days after pinaverium was discontinued, endpoints rebounded only 23.2-42.8% (P < 0.015 cf. placebo). The PTTE (P < 0.05 cf. placebo) lasted 9-17 weeks, which is similar to other antispasmodics with a 15-week treatment in striking contrast to ≥ 1 year PTTE in cognitive behavior therapy and < 1 week PTTE in serotonin antagonist treatment indicating that PTTE length markedly depends on the medication class used for the treatment and less depends on treatment length. After 17 weeks, the stage could be considered as an IBS natural history [no significant differences between pinaverium and placebo (all endpoints' P's > 0.05)], during which an average of 51.5-56.4% of patients (pool pinaverium and placebo data together) had IBS symptoms. These results provide clinical insights into efficient and cost-effective management of refractory IBS, and lend support to the IBS management that the selection of a therapy should consider both its effectiveness during treatment and its PTTE after the treatment.Trial registration number: NCT02330029 (16/08/2016).

Comparative effectiveness of 5-hydroxytryptamine 3 receptor antagonists in irritable bowel syndrome: a network meta-analysis of randomized controlled studies

BACKGROUND

There is evidence demonstrating the beneficial effects of 5-hydroxytryptamine 3 receptor antagonists (5-HT3) for the treatment of non-constipated irritable bowel syndrome (NC-IBS). We aimed to determine the comparative effectiveness of 5-HT3 antagonists in NC-IBS, as evidenced by the results of a network meta-analysis (NWM) of published relevant randomized controlled trials (RCTs).

METHODS

We searched the PubMed/Medline, EMBASE, and Cochrane Library databases for relevant RCTs through September 2020 and data from each selected RCT were extracted. A Bayesian NWM was then performed to investigate the efficacy of 5-HT3 antagonists and to explore the effectiveness rank order in treating NC-IBS patients.

RESULTS

Twenty-one eligible RCTs were identified and entered into this NWM. They included a total of 10,421 NC-IBS patients, randomized to alosetron, cilansetron, ondansetron, ramosetron, placebo, and mebeverine. The cumulative ranking probability for each intervention at the end of treatment period, was evaluated by means of surfaces under cumulative ranking (SUCRA) values. These results showed that alosetron had the best performance for global symptom improvement (SUCRA 0.82), cilansetron showed the best performance (SUCRA 0.90) for abdominal pain/discomfort improvement, while ondansetron (SUCRA 0.98) was by far the best choice concerning bowel habits/consistency improvement. The control regimens (mebeverine and placebo) represented the least efficacious interventions.

CONCLUSIONS

This NWM showed that 5-HT3 receptor antagonists performed better in comparison to control drugs. Consequently, this class of drugs may play an important role in improving the debilitating symptoms in NC-IBS patients, in particular those with diarrhea.

The placebo response rate in pharmacological trials in patients with irritable bowel syndrome: a systematic review and meta-analysis

BACKGROUND

Clinical trials in irritable bowel syndrome are associated with high placebo response rates. We aimed to identify the magnitude of the placebo response and the contributing factors to this occurrence.

METHODS

We did a systematic review and meta-analysis with a search of MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials between April 1, 1959, and April 30, 2020. We included all randomised controlled trials that compared an active pharmacotherapeutic agent with placebo and had a dichotomous outcome of response to therapy (in terms of global improvement or improvement in abdominal pain) in adults (aged ≥18 years) with irritable bowel syndrome. Exclusion criteria were trials reporting on treatment satisfaction as a dichotomous outcome of response to therapy or clinician-reported outcomes and a treatment duration of less than 4 weeks. Our main outcome was identification of the magnitude of the pooled placebo response rate for the following endpoints: global improvement, abdominal pain, and US Food and Drug Administration (FDA) endpoints. We extracted information from published reports and pooled proportions through meta-analysis with random effects. The study was registered with PROSPERO, CRD42020170908.

FINDINGS

Of the 6863 publications identified, 70 articles describing 73 randomised controlled trials were included in our analysis. The pooled placebo response rate was 27·3% (95% CI 24·3-30·9) using the global improvement endpoint, 34·4% (31·2-37·8) using the abdominal pain endpoint, and 17·9% (15·2-21·0) using the composite FDA endpoint responder definition, all with substantial heterogeneity between the trials. Studies published before 2006, and those done in Europe, with a parallel design, a run-in period of 2 weeks or less, a dose schedule of three times a day or more, or a smaller sample size of the control group were significantly associated with an increased pooled placebo response rate.

INTERPRETATION

More than a quarter of patients with irritable bowel syndrome had a placebo response in terms of global improvement, with multiple associated moderators. We recommend future trials apply a run-in period of at least 2 weeks and dose once or twice a day to minimise the placebo response rate.

FUNDING

None.

Management of irritable bowel syndrome with diarrhea: focus on eluxadoline

OBJECTIVE

We sought to summarize current recommendations for the diagnosis of diarrhea-predominant irritable bowel syndrome (IBS-D) and describe available management options, highlighting a newer US Food and Drug Administration (FDA)-approved agent, eluxadoline.

METHODS

Literature on IBS-D was assessed up to January 2020 using PubMed, with key search terms including "IBS-D diagnosis", "IBS-D management", and "eluxadoline".

RESULTS

IBS is a common gastrointestinal disorder affecting up to 14% of US adults and is particularly prevalent in women and those aged under 50. Symptoms include abdominal pain associated with altered bowel habits (i.e. diarrhea and/or constipation subtyped based on the predominant stool pattern). As IBS-D is challenging to manage with varying symptom severity, effective treatment requires a personalized management approach. Evidence-based therapeutic options endorsed by the American Gastroenterological Association and the American College of Gastroenterology can be used to effectively guide treatment. Dietary and lifestyle modifications, including adequate hydration, reducing caffeine and alcohol intake, and increasing soluble fiber intake may lead to symptom improvement. Over-the-counter medications such as loperamide are frequently recommended and may improve stool frequency and rectal urgency; however, for the outcome of abdominal pain, mixed results have been observed. Several off-label prescription medications are useful in IBS-D management, including tricyclic antidepressants, bile acid sequestrants, and antispasmodics. Three prescription medications have been approved by the FDA for IBS-D: alosetron, eluxadoline, and rifaximin.

CONCLUSIONS

IBS-D can be effectively managed in the primary care setting in the absence of alarm features. Benefits and risks of pharmacologic interventions should be weighed during treatment selection.

Evidence-based clinical practice guidelines for irritable bowel syndrome 2020

Managing irritable bowel syndrome (IBS) has attracted international attention because single-agent therapy rarely relieves bothersome symptoms for all patients. The Japanese Society of Gastroenterology (JSGE) published the first edition of evidence-based clinical practice guidelines for IBS in 2015. Much more evidence has accumulated since then, and new pharmacological agents and non-pharmacological methods have been developed. Here, we report the second edition of the JSGE-IBS guidelines comprising 41 questions including 12 background questions on epidemiology, pathophysiology, and diagnostic criteria, 26 clinical questions on diagnosis and treatment, and 3 questions on future research. For each question, statements with or without recommendations and/or evidence level are given and updated diagnostic and therapeutic algorithms are provided based on new evidence. Algorithms for diagnosis are requisite for patients with chronic abdominal pain or associated symptoms and/or abnormal bowel movement. Colonoscopy is indicated for patients with one or more alarm symptoms/signs, risk factors, and/or abnormal routine examination results. The diagnosis is based on the Rome IV criteria. Step 1 therapy consists of diet therapy, behavioral modification, and gut-targeted pharmacotherapy for 4 weeks. For non-responders, management proceeds to step 2 therapy, which includes a combination of different mechanistic gut-targeted agents and/or psychopharmacological agents and basic psychotherapy for 4 weeks. Step 3 therapy is for non-responders to step 2 and comprises a combination of gut-targeted pharmacotherapy, psychopharmacological treatments, and/or specific psychotherapy. These updated JSGE-IBS guidelines present best practice strategies for IBS patients in Japan and we believe these core strategies can be useful for IBS diagnosis and treatment globally.

Pharmacological Therapies and Their Clinical Targets in Irritable Bowel Syndrome With Diarrhea

Irritable bowel syndrome (IBS) is one of the most common disorders of the gut-brain axis, which affects approximately 4% of the global population. The Rome IV criteria define IBS as chronic or recurrent abdominal pain associated with altered bowel habits. Patients can be categorized in four subtypes: IBS with predominant constipation (IBS-C), predominant diarrhea (IBS-D), mixed bowel habits (IBS-M), and unclassified (IBS-U). IBS is associated with a lower quality of life, reduced work productivity, and high healthcare costs. When comparing subtypes, patients with IBS-D report lower disease related quality of life. Due to the scope of this review, we have solely focused on patients with IBS-D. Choosing the right pharmacological treatment in these patients remains challenging due to the heterogeneous patient population, patients' expectation of the treatment outcome, unavailability of efficacious drugs, and the multifactorial and incompletely understood underlying pathophysiology. Currently, pharmacological treatment options target individual symptoms, such as abdominal pain, altered bowel habits, and bloating. In this review, we aimed to summarize the current and recent pharmacological treatment options in IBS-D, targeting the predominant gastrointestinal symptoms. Additionally, we proposed a pharmacological treatment algorithm which healthcare professionals could use when treating individual patients with IBS-D.

ACG Clinical Guideline: Management of Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a highly prevalent, chronic disorder that significantly reduces patients' quality of life. Advances in diagnostic testing and in therapeutic options for patients with IBS led to the development of this first-ever American College of Gastroenterology clinical guideline for the management of IBS using Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) methodology. Twenty-five clinically important questions were assessed after a comprehensive literature search; 9 questions focused on diagnostic testing; 16 questions focused on therapeutic options. Consensus was obtained using a modified Delphi approach, and based on GRADE methodology, we endorse the following: We suggest that a positive diagnostic strategy as compared to a diagnostic strategy of exclusion be used to improve time to initiating appropriate therapy. We suggest that serologic testing be performed to rule out celiac disease in patients with IBS and diarrhea symptoms. We suggest that fecal calprotectin be checked in patients with suspected IBS and diarrhea symptoms to rule out inflammatory bowel disease. We recommend a limited trial of a low fermentable oligosaccharides, disacchardies, monosaccharides, polyols (FODMAP) diet in patients with IBS to improve global symptoms. We recommend the use of chloride channel activators and guanylate cyclase activators to treat global IBS with constipation symptoms. We recommend the use of rifaximin to treat global IBS with diarrhea symptoms. We suggest that gut-directed psychotherapy be used to treat global IBS symptoms. Additional statements and information regarding diagnostic strategies, specific drugs, doses, and duration of therapy can be found in the guideline.

Update on Eluxadoline for the Treatment of Irritable Bowel Syndrome with Diarrhea: Patient Selection and Perspectives

Irritable bowel syndrome (IBS) is a functional gastrointestinal (GI) disorder characterized by chronic abdominal pain associated with changes in bowel habits. It is the most common GI problem seen by gastroenterologists. IBS is a heterogenous disorder encompassing a spectrum of underlying mechanisms and clinical presentations. The pathophysiology of diarrhea-predominant form of IBS (IBS-D) remains poorly understood, and current available therapeutic options for IBS-D are limited. Eluxadoline is a novel, locally acting mixed μ- and κ-opioid receptor agonist and δ-receptor antagonist approved by the Food and Drug Administration (FDA) for treatment of adults with IBS-D. Data from two phase III clinical trials showed that approximately 25–30% of the eluxadoline-treated patients achieved composite clinical response, defined by a reduction of abdominal pain and improvement in stool consistency. Patients who achieve composite response during the first month of therapy were significantly more likely to demonstrate sustained clinical response. The most common adverse events reported with eluxadoline use were constipation, nausea and abdominal pain. The risk of abuse, dependence, or withdrawal is low. Serious adverse events associated with eluxadoline include sphincter of Oddi spasm (SOS) and pancreatitis particularly in patients without a gallbladder. Development of pancreatitis is likely secondary to SOS, but it remains unclear why pancreatitis occurs so quickly after initial doses. This adverse event profile helps guide proper selection of IBS-D patients for eluxadoline use, with important contraindications including absence of a gallbladder, biliary duct obstruction or sphincter of Oddi dysfunction, alcoholism, history of pancreatitis, or structural diseases of the pancreas. With the recent clinical trials demonstrating its efficacy, eluxadoline provides an additional option to the few existing pharmacologic interventions available for IBS-D. In this review, we discuss the drug development, efficacy and safety of eluxadoline, as well as selection criteria for identifying appropriate candidates for this medication.

Efficacy of pharmacological therapies in patients with IBS with diarrhoea or mixed stool pattern: systematic review and network meta-analysis

OBJECTIVE

Over half of patients with IBS have either diarrhoea (IBS-D) or a mixed stool pattern (IBS-M). The relative efficacy of licenced pharmacological therapies is unclear in the absence of head-to-head trials. We conducted a network meta-analysis to resolve this uncertainty.

DESIGN

We searched MEDLINE, Embase, Embase Classic, the Cochrane central register of controlled trials, and Clinicaltrials.gov through January 2019 to identify randomised controlled trials (RCTs) assessing the efficacy of licenced pharmacological therapies (alosetron, eluxadoline, ramosetron and rifaximin) in adults with IBS-D or IBS-M. Trials included in the analysis reported a dichotomous assessment of overall response to therapy, and data were pooled using a random effects model. Efficacy and safety of all pharmacological therapies were reported as a pooled relative risk with 95% CIs to summarise the effect of each comparison tested. Treatments were ranked according to their p score.

RESULTS

We identified 18 eligible RCTs (seven alosetron, five ramosetron, two rifaximin and four eluxadoline), containing 9844 patients. All were superior to placebo for the treatment of IBS-D or IBS-M at 12 weeks, according to the Food and Drug Administration (FDA)-recommended endpoint for trials in IBS. Alosetron 1 mg twice daily was ranked first for efficacy, based on the FDA-recommended composite endpoint of improvement in both abdominal pain and stool consistency, effect on global symptoms of IBS and effect on stool consistency. Ramosetron 2.5µg once daily was ranked first for effect on abdominal pain. Total numbers of adverse events were significantly greater with alosetron 1 mg twice daily and ramosetron 2.5µg once daily, compared with placebo. Rifaximin 550 mg three times daily ranked first for safety. Constipation was significantly more common with all drugs, except rifaximin 550 mg three times daily.

CONCLUSION

In a network meta-analysis of RCTs of pharmacological therapies for IBS-D and IBS-M, we found all drugs to be superior to placebo, but alosetron and ramosetron appeared to be the most effective.

Current US Food and Drug Administration-Approved Pharmacologic Therapies for the Treatment of Irritable Bowel Syndrome with Diarrhea

Irritable bowel syndrome (IBS) is a functional bowel disorder characterized by abdominal pain and alterations in stool form and/or frequency, leading to reduced quality of life. Pharmacologic agents currently approved by the US Food and Drug Administration for treatment of IBS with diarrhea (IBS-D) in adults are the nonsystemic antibiotic rifaximin, the mixed µ- and κ-opioid receptor agonist/δ-opioid antagonist eluxadoline, and the selective serotonin 5-HT₃ antagonist alosetron (the last of which is indicated only in women with severe IBS-D refractory to conventional therapy). Both eluxadoline and alosetron are administered as chronic daily therapies; rifaximin is given as a 2-week course of treatment with repeat courses administered as needed for symptom recurrence. Presumed mechanisms of action of rifaximin include modulation of the gut microbiota, anti-inflammatory activity, normalization of visceral hypersensitivity, and reduction in intestinal permeability. Eluxadoline targets opioid receptors in the gastrointestinal (GI) tract, resulting in decreased GI motility, fluid secretion, and visceral pain perception. Alosetron antagonizes serotonergic afferent neural signals and also slows GI motility. The efficacy and safety of these agents have been investigated in several rigorous clinical trials, and it has been demonstrated that they improve global and individual IBS symptoms. This review highlights the pivotal efficacy and safety data of the three pharmacologic agents currently indicated in the USA for the management of IBS-D in adults.Funding: Salix Pharmaceuticals.

Alosetron versus traditional pharmacotherapy in clinical practice: effects on resource use, health-related quality of life, safety and symptom improvement in women with severe diarrhea-predominant irritable bowel syndrome

OBJECTIVE

Severe diarrhea-predominant irritable bowel syndrome (IBS-D) is associated with decreased health-related quality of life (HRQOL) and increased health care costs. Treatment recommendations for IBS-D often start with traditional pharmacotherapy (TP), with escalation to alosetron, rifaximin or eluxadoline if there is no success. There has been no previous head-to-head clinical trial comparing IBS-D treatment outcome for alosetron versus TP. This study, GSK protocol S3B30020, evaluated resource use, work productivity, health-related quality of life and global symptom response in women with IBS-D who were treated with alosetron or TP.

METHODS

A total of 1956 patients who met criteria for severe IBS-D were randomized to treatment with alosetron 1 mg twice daily (BID) or only TP for up to 24 weeks. Work productivity and resource use were evaluated by standard questionnaires, HRQOL by the IBSQOL instrument and IBS symptoms by the Global Improvement Scale (GIS).

RESULTS

Compared to only TP, alosetron-treated patients reported: (1) fewer clinic/office visits for any health problem (p = .0181) or for IBS-D (p = .0004); (2) reduced use of over-the-counter medications for IBS-D (p < .0001); (3) fewer days of lost work productivity (p < .0001); (4) decreased restriction of social and outdoor activities (p < .0001); and (5) greater global improvement in IBS-D symptoms (p < .0001). Alosetron treatment improved HRQOL scores for all domains (p < .0001). Incidence of adverse events during alosetron use was not remarkable and was similar to that previously reported.

CONCLUSIONS

Alosetron 1 mg BID significantly reduced health care utilization and lost productivity, and significantly improved global IBS symptoms, HRQOL, and participation in outdoor and social activities compared with treatment response to TP.

Short-course therapy for diarrhea-predominant irritable bowel syndrome: understanding the mechanism, impact on gut microbiota, and safety and tolerability of rifaximin

Irritable bowel syndrome (IBS) is a common gastrointestinal (GI) disorder characterized by abdominal pain that occurs with defecation or alterations in bowel habits. Further classification is based on the predominant bowel habit: constipation-predominant IBS, diarrhea-predominant IBS (IBS-D), or mixed IBS. The pathogenesis of IBS is unclear and is considered multifactorial in nature. GI dysbiosis, thought to play a role in IBS pathophysiology, has been observed in patients with IBS. Alterations in the gut microbiota are observed in patients with small intestinal bacterial overgrowth, and overgrowth may occur in a subset of patients with IBS. The management of IBS includes therapies targeting the putative factors involved in the pathogenesis of the condition. However, many of these interventions (eg, eluxadoline and alosetron) require long-term, daily administration and have important safety considerations. Agents thought to modulate the gut microbiota (eg, antibiotics and probiotics) have shown potential benefits in clinical studies. However, conventional antibiotics (eg, neomycin) are associated with several adverse events and/or the risk of bacterial antibiotic resistance, and probiotics lack uniformity in composition and consistency of response in patients. Rifaximin, a nonsystemic antibiotic administered as a 2-week course of therapy, has been shown to be safe and efficacious for the treatment of IBS-D. Rifaximin exhibits a favorable benefit-to-harm ratio when compared with daily therapies for IBS-D (eg, alosetron and tricyclic antidepressants), and rifaximin was not associated with the emergence of bacterial antibiotic resistance. Thus, short-course therapy with rifaximin is an appropriate treatment option for IBS-D.

Guidelines on the management of irritable bowel syndrome: In memory of Professor Witold Bartnik

These guidelines constitute an update of the previous "Recommendations on the management of irritable bowel syndrome" issued in 2008. They have been developed by a Task Force organized by the Governing Board of the Polish Society of Gastroenterology. They discuss, with particular emphasis on new scientific data covering papers published since 2008, the aetiology, epidemiology, clinical presentation, diagnostic principles and criteria for the diagnosis, and recommendations for the treatment of irritable bowel syndrome (IBS). The English-language acronym for the syndrome (IBS) has become popular in medical and popular scientific language. It is also widely recognized by patients who identify with this diagnosis. Therefore, in the discussed guidelines, this is what we will use.

Alosetron use in clinical practice: significant improvement in irritable bowel syndrome symptoms evaluated using the US Food and Drug Administration composite endpoint

BACKGROUND

Alosetron is approved to treat women with severe IBS and diarrhea (IBS-D) who have failed standard therapy. In our study, we aimed to evaluate alosetron efficacy using new US Food and Drug Administration (FDA) endpoints and utilization in clinical practice.

METHODS

This prospective, open-label, multicenter, observational 12-week study evaluated women with severe IBS-D enrolled in the alosetron prescribing program. The coprimary FDA endpoints were changes from baseline in stool consistency and abdominal pain severity. Responders achieved a 30% decrease compared with baseline in weekly average of the worst abdominal pain in the past 24 h, and a 50% or greater reduction from baseline in the number of days/week with at least one stool of type 6 (mushy) or type 7 (watery) consistency. Secondary endpoints included changes from baseline in stool frequency, fecal urgency and fecal incontinence.

RESULTS

Enrolled patients (n = 192) were primarily White (90.6%), with a mean age of 44.5 years. Patient and physician rating of IBS severity was between moderate and severe (85.9% concordance, Spearman coefficient 0.429, p < 0.0001). Alosetron 0.5 mg twice daily (82.8%) was the most common dosing regimen. A total of 152 alosetron-treated patients completed the study. Of 105 fully evaluable patients, 45% met the FDA composite endpoint responder criteria for ⩾50% of the study period. Improvements in all individual symptoms were statistically significant compared with baseline. There were no serious adverse events, cases of colonic ischemia, or complications of constipation.

CONCLUSION

In a clinical practice setting study, alosetron demonstrated treatment success using a rigorous FDA composite endpoint and also improved multiple other IBS symptoms, including fecal urgency and incontinence in women with severe IBS-D [ClinicalTrials.gov identifier: NCT01257477].

Lack of an Effect of Gastric Capsaicin on the Rectal Component of the Gastrocolonic Response

Luminal capsaicin induces local and distant reflexes in the upper gastrointestinal tract and stimulates lower gastrointestinal symptoms in susceptible persons. We aimed to evaluate the effect of gastric capsaicin on rectal motor function and sensation.

METHODS

Eighteen healthy volunteers participated twice, at least 1 week apart, in this double-blind, placebo-controlled crossover study. Participants swallowed a gastric tube for capsaicin or saline infusion. A barostat tube was placed in the rectum to measure rectal tone before and during gastric capsaicin (40 µg/ml, 2.5 ml/min) or placebo infusion and to conduct distension experiments before and after gastric infusions. Gastric infusions were terminated after 60 min or when epigastric discomfort occurred. Differences in rectal tone, compliance, and sensitivity between gastric placebo and gastric capsaicin were determined.

RESULTS

On both study days, basal rectal volumes, compliance, and sensitivity parameters were comparable (NS) before gastric infusions. Gastric capsaicin infusion induced epigastric discomfort that necessitated termination of infusion after 29.6 ± 12.3 min (saline: 54.7 ± 8.9 min; p < 0.01). Rectal tone, aggregate perception scores, and rectal compliance did not differ between placebo and capsaicin trials (p > 0.05). Rectal tone increased significantly only when capsaicin induced epigastric discomfort (p < 0.05). The reproducibility of the barostat trial was acceptable with significant correlations of volumes, pressures (< 0.05; r ² from 0.41 to 0.55), rectal compliance (p < 0.01; r ² = 0.44), and aggregate perception scores (p values all < 0.05; r ² from 0.44 to 0.0.65) between the two barostat trials.

CONCLUSION

Gastric perfusion with capsaicin does not directly influence rectal physiology through a reflex arc.

Efficacy of individualised diets in patients with irritable bowel syndrome: a randomised controlled trial

Background

Patients with irritable bowel syndrome (IBS) are often placed on diets guided by food intolerance assays, although these have not been validated. We assessed the effects of individualised diets in patients with IBS guided by a leucocyte activation test.

Methods

This is a parallel-group, double-blind, randomised controlled trial of 58 adults with IBS seen at an academic health centre in Northeast USA. Peripheral venous blood was analysed using a leucocyte activation test; individual foods were reported to produce positive or negative results. Participants were randomised to a 4-week diet with either individualised guidance to eliminate foods with positive assay results and allow foods with negative assay results (intervention), or with individualised guidance, matched in rigour and complexity, to eliminate foods with negative assay results and allow foods with positive assay results (comparison). The primary outcome was between-group differences in the IBS Global Improvement Scale (GIS). Secondary outcomes included reductions in IBS Symptom Severity Scale (SSS) scores and increases in IBS Adequate Relief (AR) and Quality of Life (QOL) scores. An aptamer-based proteomic analysis was conducted in strong responders.

Results

The intervention group had significantly greater increases in mean GIS score after 4 weeks (0.86 vs comparison; 95% CI 0.05 to 1.67; p=0.04) and 8 weeks (1.22 vs comparison; 95% CI 0.22 to 2.22; p=0.02). The intervention group also had significantly greater reductions in mean SSS score at 4 weeks (–61.78 vs comparison; 95% CI –4.43 to –119.14; p=0.04) and 8 weeks (–66.42 vs comparison; 95% CI –5.75 to –127.09; p=0.03). There were no significant differences between intervention and comparison groups in mean AR or QOL scores. A reduction in neutrophil elastase concentration was associated with reduced symptoms.

Conclusions

Elimination diets guided by leucocyte activation tests reduced symptoms. These findings could lead to insights into the pathophysiology of IBS.

Trial registration number

NCT02186743.

Efficacy and safety of 5-hydroxytryptamine 3 receptor antagonists in irritable bowel syndrome: A systematic review and meta-analysis of randomized controlled trials

AIM

We assessed the efficacy and safety of 5-hydroxytryptamine (5-HT3) receptor antagonists in adults with non-constipated irritable bowel syndrome (IBS) or diarrhea-predominant IBS (IBS-D).

METHODS

We searched PubMed, MEDLINE, EMBASE, and the Cochrane Controlled Trials Register for randomized controlled trials (RCTs) involving adults with non-constipated IBS or IBS-D that compared 5-HT3 receptor antagonists with placebo or other conventional treatment. Dichotomous symptom data were pooled to obtain the relative risk (RR) and 95% confidence intervals (CIs) for improving global IBS symptoms, abdominal pain and abnormal bowel habits, or stool consistency symptoms after therapy, and adverse events, including constipation. Meta- analysis was performed with Mantel Haenszel method using Revman 5.3 software.

RESULTS

We included 21 RCTs; 16 were high quality (Jadad score ≥ 4). The pooled RR of global IBS symptoms improved by 5-HT3 receptor antagonists versus placebo or mebeverine was 1.56 (95% CI: 1.43-1.71); alosetron, ramosetron, and cilansetron had similar treatment effects. The pooled RR of abdominal pain relieved by 5-HT3 receptor antagonists versus placebo was 1.33 (95% CI: 1.26-1.39). The pooled RR showed that 5-HT3 receptor antagonists improved abnormal bowel habits or stool consistency symptoms (RR = 1.63, 95% CI: 1.33, 1.99). The pooled RR of adverse events following 5-HT3 receptor antagonist treatment was 1.15 (95% CI: 1.08, 1.22). Subgroup analysis indicated that alosetron had a high rate of adverse effects (RR = 1.16, 95% CI: 1.08, 1.25); adverse events following ramosetron treatment were not statistically significantly different. 5-HT3 receptor antagonists were likelier to cause constipation: the pooled RR of constipation developing with 5-HT3 receptor antagonist versus placebo was 3.71 (95% CI: 2.98-4.61). However, constipation was likelier in patients with non-constipated IBS after taking 5-HT3 receptor antagonists than in patients with IBS-D only (non-constipated IBS and IBS-D: RR = 5.28 [95% CI: 3.93, 7.08] vs. IBS-D only 3.24 [2.54, 4.12]).

CONCLUSIONS

Ramosetron, cilansetron, ondansetron, and alosetron are effective for treating non-constipated IBS and IBS-D. Our systematic review found rare serious adverse events.

Safety of Eluxadoline in Patients with Irritable Bowel Syndrome with Diarrhea

OBJECTIVES

Eluxadoline is a mixed μ-opioid receptor (OR) and κ-OR agonist and δ-OR antagonist, approved for the treatment of irritable bowel syndrome with diarrhea (IBS-D). This analysis evaluated the safety and tolerability of eluxadoline 75 and 100 mg twice daily (BID) in one Phase 2 (IBS-2001) and two Phase 3 (IBS-3001 and IBS-3002) studies.

METHODS

Adults with IBS-D (Rome III criteria) were randomized to placebo or eluxadoline (75 or 100 mg) BID for 12 (IBS-2001), 26 (IBS-3002), or 52 (IBS-3001) weeks. Safety data were pooled. Adverse events (AEs) were assessed, with special focus on opioid-related AEs, including suspected sphincter of Oddi spasm (SOS) events.

RESULTS

2,776 patients were included in the enrolled set; the safety set comprised 2,814 patients, based on actual treatments received. The most frequent AEs in the placebo and eluxadoline 75 and 100 mg groups were constipation (2.5, 7.4, and 8.1%, respectively) and nausea (5.0, 8.1, and 7.1%, respectively); discontinuation due to constipation was uncommon (0.3, 1.1, and 1.5%, respectively). Ten SOS events (10/1,839; 0.5%) occurred in eluxadoline-treated patients, manifesting as acute abdominal pain with elevated aminotransferases or lipase, or pancreatitis; all occurred in patients without a gallbladder. Eight of these events occurred with the higher dose of eluxadoline, within 1 week of initiation of therapy, and all resolved with eluxadoline discontinuation. There were five events independently adjudicated as pancreatitis not associated with SOS, three of which were associated with heavy alcohol use.

CONCLUSIONS

Eluxadoline was well tolerated in Phase 2 and 3 trials, with constipation and nausea the most common AEs. Consistent with the known adverse effects of opioid agonists, clinically apparent SOS events were observed in eluxadoline-treated patients. All occurred in patients without a gallbladder and the majority were observed in patients on the higher dose of eluxadoline, suggesting a possible association.

Randomised clinical trial: exploratory phase 2 study of ONO-2952 in diarrhoea-predominant irritable bowel syndrome

BACKGROUND

ONO-2952 is a novel and selective inhibitor of translocator protein 18 kDa that reduces stress-induced defecation and visceral hyperalgesia in rat models.

AIM

To evaluate the efficacy and safety of ONO-2952 in females with irritable bowel syndrome with diarrhoea in an exploratory proof-of-concept study.

METHODS

A randomised, double-blind, placebo-controlled study was conducted at 49 US centres. Two hundred subjects with irritable bowel syndrome with diarrhoea (Rome III criteria) were randomised to ONO-2952 20 mg, or 60 mg, or placebo. Subjects recorded irritable bowel syndrome symptoms daily during a 2-week baseline period, the 4-week treatment period and for 4 weeks post-treatment. The co-primary endpoints were change from baseline to week 4 in abdominal pain, stool consistency and stool frequency.

RESULTS

Improvements in irritable bowel syndrome symptoms were seen with ONO-2952 over placebo in per-protocol analyses for all three co-primary endpoints, but these did not reach statistical significance at the 5% level. The largest improvement was seen with ONO-2952 60 mg. ONO-2952 was well tolerated with a safety profile similar to that of placebo. Most adverse events were mild or moderate in severity and not treatment related.

CONCLUSION

ONO-2952 showed evidence of clinical efficacy in reducing irritable bowel syndrome-related symptoms in female subjects with irritable bowel syndrome with diarrhoea, and further evaluation is, therefore, warranted to assess its potential as a treatment for irritable bowel syndrome with diarrhoea (NCT01844180).

Diagnosis and treatment of diarrhea-predominant irritable bowel syndrome

Irritable bowel syndrome (IBS) is one of the most common gastrointestinal disorders worldwide. The economic impact of IBS on the health care system is substantial, as is the personal impact on patients. Patients with diarrhea-predominant IBS (IBS-D) comprise a substantial proportion of the overall IBS population. Primary care providers are often the first point of contact for patients with IBS-D and can accurately diagnose IBS after a careful history and examination without extensive diagnostic tests. Several pharmacologic treatments (eg, loperamide, alosetron, and antidepressants) and non-pharmacologic treatments (eg, dietary modification and probiotics) are available for IBS-D, but restrictions on use (eg, alosetron) or the lack of controlled trial data showing reductions in both global and individual IBS-D symptoms (eg, bloating, pain and stool frequency) emphasize the need for alternative treatment options. Two newer medications (eluxadoline and rifaximin) were approved in May 2015 for the treatment of IBS-D, and represent new treatment options for this common gastrointestinal condition.

Diagnosis and treatment of diarrhea-predominant irritable bowel syndrome

Irritable bowel syndrome (IBS) is one of the most common gastrointestinal disorders worldwide. The economic impact of IBS on the health care system is substantial, as is the personal impact on patients. Patients with diarrhea-predominant IBS (IBS-D) comprise a substantial proportion of the overall IBS population. Primary care providers are often the first point of contact for patients with IBS-D and can accurately diagnose IBS after a careful history and examination without extensive diagnostic tests. Several pharmacologic treatments (eg, loperamide, alosetron, and antidepressants) and non-pharmacologic treatments (eg, dietary modification and probiotics) are available for IBS-D, but restrictions on use (eg, alosetron) or the lack of controlled trial data showing reductions in both global and individual IBS-D symptoms (eg, bloating, pain and stool frequency) emphasize the need for alternative treatment options. Two newer medications (eluxadoline and rifaximin) were approved in May 2015 for the treatment of IBS-D, and represent new treatment options for this common gastrointestinal condition.

Eluxadoline for Irritable Bowel Syndrome with Diarrhea

Background Effective and safe treatments are needed for patients who have irritable bowel syndrome (IBS) with diarrhea. We conducted two phase 3 trials to assess the efficacy and safety of eluxadoline, a new oral agent with mixed opioid effects (μ- and κ-opioid receptor agonist and δ-opioid receptor antagonist), in patients with IBS with diarrhea. Methods We randomly assigned 2427 adults who had IBS with diarrhea to eluxadoline (at a dose of 75 mg or 100 mg) or placebo twice daily for 26 weeks (IBS-3002 trial) or 52 weeks (IBS-3001 trial). The primary end point was the proportion of patients who had a composite response of decrease in abdominal pain and improvement in stool consistency on the same day for at least 50% of the days from weeks 1 through 12 and from weeks 1 through 26. Results For weeks 1 through 12, more patients in the eluxadoline groups (75 mg and 100 mg) than in the placebo group reached the primary end point (IBS-3001 trial, 23.9% with the 75-mg dose and 25.1% with the 100-mg dose vs. 17.1% with placebo; P=0.01 and P=0.004, respectively; IBS-3002 trial, 28.9% and 29.6%, respectively, vs. 16.2%; P<0.001 for both comparisons). For weeks 1 through 26, the corresponding rates in IBS-3001 were 23.4% and 29.3% versus 19.0% (P=0.11 and P<0.001, respectively), and the corresponding rates in IBS-3002 were 30.4% and 32.7% versus 20.2% (P=0.001 and P<0.001, respectively). The most common adverse events associated with 75 mg of eluxadoline and 100 mg of eluxadoline, as compared with placebo, were nausea (8.1% and 7.5% vs. 5.1%), constipation (7.4% and 8.6% vs. 2.5%), and abdominal pain (5.8% and 7.2% vs. 4.1%). Pancreatitis developed in 5 (2 in the 75-mg group and 3 in the 100-mg group) of the 1666 patients in the safety population (0.3%). Conclusions Eluxadoline is a new therapeutic agent that reduced symptoms of IBS with diarrhea in men and women, with sustained efficacy over 6 months in patients who received the 100-mg dose twice daily. (Funded by Furiex Pharmaceuticals, an affiliate of Allergan; IBS-3001 and IBS-3002 ClinicalTrials.gov numbers, NCT01553591 and NCT01553747 , respectively.).

Novel Therapies in IBS-D Treatment

OPINION STATEMENT

Irritable bowel syndrome (IBS) is a common gastrointestinal disease characterized by abdominal pain and change in bowel habits. IBS diarrhea predominant (IBS-D), which is arguably the most common subset of IBS, is also associated with rectal urgency, increased frequency, abdominal bloating, and loose to watery stools. Current treatments for diarrhea include mu-opioid agonists (i.e., loperamide, lomotil) and bile acid sequestrants (i.e., cholestyramine) while treatments for abdominal pain include antispasmodics (i.e., hyoscyamine, dicyclomine) and tricyclic antidepressants (i.e., amitriptyline). There are currently 3 FDA-approved treatments for IBS-D, which have been shown to improve both abdominal pain and diarrhea. Alosetron was initially approved by FDA 2000; however, its use is now limited to women with severe IBS-D symptoms refractory to other treatment. Eluxadoline, a mixed mu-opioid agonist, and rifaximin, a broad spectrum gut specific antibiotic, were both FDA approved in 2015. Eluxadoline has been shown to relieve abdominal pain and stool consistency in appropriate candidates. While large trials already showed the efficacy of rifaximin in treating non-constipated IBS for bloating, stool consistency, and abdominal pain, the recent TARGET 3 trial demonstrates that retreatment is also effective. While these new treatments significantly expand options for patients suffering from IBS-D, there is likely to remain a need for additional safe and effective therapies.

Irritable bowel syndrome: modern concepts and management options

Irritable bowel syndrome is the most common functional gastrointestinal disorder, manifesting as abdominal pain/discomfort and altered bowel function. Despite affecting as many as 20% of adults, a lack of understanding of etiopathogenesis and evaluation strategies results in diagnostic uncertainty, and in turn frustration of both the physician and the patient. This review summarizes the current literature on the diagnosis and management of irritable bowel syndrome, with attention to evidence-based approaches. A 4-step treatment strategy that has been used successfully in our tertiary referral practice is presented and should lead to successful therapeutic outcomes in the majority of patients with irritable bowel syndrome.

Evidence-based clinical practice guidelines for irritable bowel syndrome

New strategies for the care of irritable bowel syndrome (IBS) are developing and several novel treatments have been globally produced. New methods of care should be customized geographically because each country has a specific medical system, life style, eating habit, gut microbiota, genes and so on. Several clinical guidelines for IBS have been proposed and the Japanese Society of Gastroenterology (JSGE) subsequently developed evidence-based clinical practice guidelines for IBS. Sixty-two clinical questions (CQs) comprising 1 definition, 6 epidemiology, 6 pathophysiology, 10 diagnosis, 30 treatment, 4 prognosis, and 5 complications were proposed and statements were made to answer to CQs. A diagnosis algorithm and a three-step treatment was provided for patients with chronic abdominal pain or abdominal discomfort and/or abnormal bowel movement. If more than one alarm symptom/sign, risk factor and/or routine examination is positive, colonoscopy is indicated. If all of them, or the subsequent colonoscopy, are/is negative, Rome III or compatible criteria is applied. After IBS diagnosis, step 1 therapy consisting of diet therapy, behavioral modification and gut-targeted pharmacotherapy is indicated for four weeks. Non-responders to step 1 therapy proceed to the second step that includes psychopharmacological agents and simple psychotherapy for four weeks. In the third step, for patients non-responsive to step 2 therapy, a combination of gut-targeted pharmacotherapy, psychopharmacological treatments and/or specific psychotherapy is/are indicated. Clinical guidelines and consensus for IBS treatment in Japan are well suited for Japanese IBS patients; as such, they may provide useful insight for IBS treatment in other countries around the world.

Recent advances in pharmacological treatment of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a highly prevalent functional disorder that reduces patients’ quality of life. It is a chronic disorder characterized by abdominal pain or discomfort associated with disordered defecation in the absence of identifiable structural or biochemical abnormalities. IBS imposes a significant economic burden to the healthcare system. Alteration in neurohumoral mechanisms and psychological factors, bacterial overgrowth, genetic factors, gut motility, visceral hypersensitivity, and immune system factors are currently believed to influence the pathogenesis of IBS. It is possible that there is an interaction of one or more of these etiologic factors leading to heterogeneous symptoms of IBS. IBS treatment is predicated upon the patient’s most bothersome symptoms. Despite the wide range of medications and the high prevalence of the disease, to date no completely effective remedy is available. This article reviews the literature from January 2008 to July 2013 on the subject of IBS peripherally acting pharmacological treatment. Drugs are categorized according to their administration for IBS-C, IBS-D or abdominal pain predominant IBS.

Vagal anandamide signaling via cannabinoid receptor 1 contributes to luminal 5-HT modulation of visceral nociception in rats

Serotonin (5-HT) plays pivotal roles in the pathogenesis of postinfectious irritable bowel syndrome (PI-IBS), and luminal 5-HT time-dependently modulates visceral nociception. We found that duodenal biopsies from PI-IBS patients exhibited increased 5-HT and decreased anandamide levels and that decreased anandamide was associated with abdominal pain severity, indicating a link between 5-HT and endocannabinoid signaling pathways in PI-IBS. To understand this, we investigated the role of endocannabinoids in 5-HT modulation of visceral nociception in a rat model. Acute intraduodenally applied 5-HT attenuated the visceromotor response (VMR) to colorectal distention, and this was reversed by the cannabinoid receptor 1 (CB1) antagonist AM251. Duodenal anandamide (but not 2-arachidonoylglycerol) content was greatly increased after luminal 5-HT treatment. This effect was abrogated by the 5-HT 3 receptor (5-HT3R) antagonist granisetron, which was luminally delivered to preferentially target vagal terminals. Chemical denervation of vagal afferents blocked 5-HT-evoked antinociception and anandamide release. Chronic luminal 5-HT exposure for 5 days increased baseline VMR and VMR post-5-HT (days 4 and 5). Duodenal levels of anandamide and N-acyl-phosphatidylethanolamine-specific phospholipase D (NAPE-PLD, the anandamide-synthesizing enzyme) protein gradually declined from day 1 to 5. The time-dependent effects of 5-HT were abolished by daily granisetron pretreatment. Daily pretreatment with CB1 agonists or anandamide from day 3 attenuated 5-HT-induced hyperalgesia. These data suggest that vagal 5-HT3R-mediated duodenal anandamide release contributes to acute luminal 5-HT-induced antinociception via CB1 signaling, whereas decreased anandamide is associated with hyperalgesia upon chronic 5-HT treatment. Further understanding of peripheral vagal anandamide signaling may provide insights into the mechanisms underlying 5-HT-related IBS.

Evaluating the functional net value of pharmacologic agents in treating irritable bowel syndrome

BACKGROUND

The recent FDA provisional endpoint incorporates a one-tailed measure of improvement for IBS based on the underlying motility complaint. However, motility exists along a spectrum. Patients may experience diarrhoea resulting from therapy for their constipation-predominant IBS (IBS-C) or constipation during treatment for diarrhoea-predominant IBS (IBS-D), but still meet a unidirectional motility-based FDA endpoint.

AIM

To weigh the reported efficacy of existing therapies based on patient-reported outcomes with negative intestinal side effects in controlled clinical trial data.

METHODS

We analysed the difference between 'attributable risk' of efficacy based on number needed to treat (NNT) in the literature and percentage of adverse events (AE) of opposite intestinal complaints in placebo-controlled trials identified through a literature search of IBS trials. This calculation was coined 'functional net value' (FNV) or net benefit of the given drug.

RESULTS

For treating IBS-C, lubiprostone caused diarrhoea in excess of placebo in 3.9% of patients, leading to a FNV of 3.9 percentage units. Linaclotide caused diarrhoea in 15.3% resulting in negative FNV (-1.0 percentage unit). For IBS-D, alosetron and tricyclic anti-depressants caused constipation among a respective 16.9% and 13.0% resulting in a FNV of -3.6 and -0.5 percentage units. Among all therapies, only rifaximin did not cause the adverse event opposite the underlying motility complaint and the drug only had benefit, not detriment.

CONCLUSIONS

Functional net value (FNV) offers a method of evaluating the net benefit of a drug in IBS. Most IBS treatments have a negative effect on IBS that exceeds the benefits.

Adverse events appear to unblind clinical trials in irritable bowel syndrome

BACKGROUND

Clinical trial design is challenging in irritable bowel syndrome (IBS) due in part to a high placebo effect. We postulated that the mere presence of an adverse event (AE) may unmask patients in clinical trials who are assigned to the active agent, and this may lead to higher reported efficacy.

METHODS

We evaluated therapies receiving at least a Grade 1B from the American College of Gastroenterology Task Force for IBS or which passed recent phase III clinical trials. Therapies with AE data derived from less than 50 patients in each study arm were excluded. Statistically significant excess AE were identified, risk difference was calculated for each AE, and incidence of AE in the treatment arm was reported. We examined the relationship of attributable drug benefit, defined as the reciprocal of number-needed-to-treat found in literature, with various measures of AE incidence.

KEY RESULTS

Attributable drug benefit correlated significantly with average AE risk difference, calculated as treatment arm AE incidence minus placebo arm AE incidence (R(2) = 0.70, p = 0.039), and also with highest treatment arm AE incidence (R(2) = 0.70, p = 0.038) for each therapy. There were also trends toward correlation with average treatment arm AE incidence (R(2) = 0.54, p = 0.096) and highest AE risk difference (R(2) = 0.63, p = 0.059) for each therapy.

CONCLUSIONS & INFERENCES

Our study suggests that higher AE incidence on active therapy is associated with more beneficial patient-reported outcomes in IBS clinical trials. This raises the issue of spontaneous unblinding.

Alosetron: an effective treatment for diarrhea-predominant irritable bowel syndrome

Serotonin (5-HT) is one of the key mediators of gut motility, secretion and sensation. Most 5-HT is localized in the gastrointestinal tract. Particularly important for gut function and regulation are the 5-HT(1P), 5-HT(3) and 5-HT(4) receptors. These receptors have been the focus of research evaluating the pathophysiologic mechanisms of irritable bowel syndrome (IBS) as well as targets for the development of novel agents to treat irritable bowel syndrome. Alosetron is one of three 5-HT(3) antagonists currently available. The other two, ondansetron and granisetron, are primarily used in the treatment of chemotherapy-induced nausea and vomiting. Alosetron, which slows gut transit, has been approved for the treatment of severe diarrhea-predominant IBS (IBS-D) in women. This review will examine the common, yet therapeutically challenging, disorder IBS, as well as the role of alosetron in the treatment of IBS-D.

Catechol-O-methyltransferase val158met polymorphism predicts placebo effect in irritable bowel syndrome

Identifying patients who are potential placebo responders has major implications for clinical practice and trial design. Catechol-O-methyltransferase (COMT), an important enzyme in dopamine catabolism plays a key role in processes associated with the placebo effect such as reward, pain, memory and learning. We hypothesized that the COMT functional val158met polymorphism, was a predictor of placebo effects and tested our hypothesis in a subset of 104 patients from a previously reported randomized controlled trial in irritable bowel syndrome (IBS). The three treatment arms from this study were: no-treatment (“waitlist”), placebo treatment alone (“limited”) and, placebo treatment “augmented” with a supportive patient-health care provider interaction. The primary outcome measure was change from baseline in IBS-Symptom Severity Scale (IBS-SSS) after three weeks of treatment. In a regression model, the number of methionine alleles in COMT val158met was linearly related to placebo response as measured by changes in IBS-SSS (p = .035). The strongest placebo response occurred in met/met homozygotes treated in the augmented placebo arm. A smaller met/met associated effect was observed with limited placebo treatment and there was no effect in the waitlist control. These data support our hypothesis that the COMT val158met polymorphism is a potential biomarker of placebo response.

Randomised clinical trial: alosetron improves quality of life and reduces restriction of daily activities in women with severe diarrhoea-predominant IBS

BACKGROUND

Patients with irritable bowel syndrome with diarrhoea (IBS-D) experience restriction in daily activities and decreased health-related quality of life (QOL).

AIM

To investigate effects of alosetron on patient-reported health-related QOL, satisfaction and productivity in women with severe IBS-D.

METHODS

A total of 705 women (severe IBS-D, Rome II criteria) randomised to alosetron 0.5 mg QD, 1 mg QD, 1 mg BID, or placebo for 12 weeks were studied. IBSQOL, treatment satisfaction, daily activities, and lost workplace productivity (LWP) were evaluated at randomisation and Week 12.

RESULTS

One or more doses of alosetron significantly improved all IBSQOL domains except for sexual function from baseline vs. placebo. The magnitude of IBSQOL changes was consistent with a clinically meaningful effect. Alosetron 0.5 mg QD and 1 mg BID significantly reduced IBS interference with social/leisure activities and LWP from baseline vs. placebo [social/leisure (mean ±S.E.) days lost: -6.7 ± 0.8, -7.0 ± 0.9, P < 0.01; LWP (mean ± S.E.) h lost: -11.0 ± 3.3, -21.1 ± 4.1, P < 0.05 respectively]. Significantly more patients treated with alosetron reported satisfaction vs. placebo. Improvements in IBSQOL, LWP, and treatment satisfaction significantly correlated with global improvement of IBS symptoms. The incidence of adverse events with alosetron was low with constipation being the most commonly reported event. A single case of ischaemic colitis occurred, in a patient receiving alosetron 0.5 mg QD.

CONCLUSIONS

In women with severe IBS-D, alosetron treatment, including 0.5 mg QD, resulted in statistically significant and clinically relevant improvements in health-related QOL, restriction of daily activities and treatment satisfaction over placebo. IBS symptom improvement corresponded with positive changes in IBSQOL, LWP and treatment satisfaction.

Effect of gender on prevalence of irritable bowel syndrome in the community: systematic review and meta-analysis

OBJECTIVES

Irritable bowel syndrome (IBS) is thought to be commoner in women. However, no systematic review has confirmed whether this is the case, or assessed whether any proposed female preponderance remains stable according to geography and criteria used to define IBS. Nor has effect of gender on subtype of IBS been examined systematically.

METHODS

MEDLINE, EMBASE, and EMBASE Classic were searched (up to October 2011) to identify population-based studies reporting prevalence of IBS in adults (≥15 years) according to gender, and defined using symptom-based criteria, or questionnaire. The prevalence of IBS in women and men was extracted for all studies, and according to study location and diagnostic criteria used, and compared using odds ratios (ORs) with 95% confidence intervals (CIs). Prevalence of each subtype of IBS, according to predominant stool pattern, was compared in women and men with IBS.

RESULTS

Of the 390 papers evaluated, 56 studies containing 188,229 subjects were eligible. The OR for IBS in women, compared with men, in all studies was 1.67 (95% CI: 1.53-1.82). Prevalence of IBS was not significantly higher in women, compared with men, in South Asian, South American, or African studies. The OR was highest with the Rome I criteria (1.99; 95% CI: 1.76-2.25), and lowest with the Rome II criteria (1.40; 95% CI: 1.24-1.59). Women with IBS were more likely to exhibit the constipation-predominant subtype (OR: 2.38; 95% CI: 1.45-3.92), and less likely to meet criteria for the diarrhea-predominant subtype (OR: 0.45; 95% CI: 0.32-0.65) than men with IBS.

CONCLUSIONS

Prevalence of IBS appeared modestly higher in women, and this remained relatively stable according to geography and criteria used to define its presence. However, among individuals with IBS, subtypes varied according to gender.

Targeted therapies for diarrhea-predominant irritable bowel syndrome

Irritable bowel syndrome (IBS) causes gastrointestinal symptoms such as abdominal pain, bloating, and bowel pattern abnormalities, which compromise patients’ daily functioning. Common therapies address one or two IBS symptoms, while others offer wider symptom control, presumably by targeting pathophysiologic mechanisms of IBS. The aim of this targeted literature review was to capture clinical trial reports of agents receiving the highest recommendation (Grade 1) for treatment of IBS from the 2009 American College of Gastroenterology IBS Task Force, with an emphasis on diarrhea-predominant IBS. Literature searches in PubMed captured articles detailing randomized placebo-controlled trials in IBS/diarrhea-predominant IBS for agents receiving Grade I (strong) 2009 American College of Gastroenterology IBS Task Force recommendations: tricyclic antidepressants, nonabsorbable antibiotics, and the 5-HT₃ receptor antagonist alosetron. Studies specific for constipation-predominant IBS were excluded. Tricyclic antidepressants appear to improve global IBS symptoms but have variable effects on abdominal pain and uncertain tolerability; effects on stool consistency, frequency, and urgency were not adequately assessed. Nonabsorbable antibiotics show positive effects on global symptoms, abdominal pain, bloating, and stool consistency but may be most efficacious in patients with altered intestinal microbiota. Alosetron improves global symptoms and abdominal pain and normalizes bowel irregularities, including stool frequency, consistency, and fecal urgency. Both the nonabsorbable antibiotic rifaximin and the 5-HT₃ receptor antagonist alosetron improve quality of life. Targeted therapies provide more complete relief of IBS symptoms than conventional agents. Familiarization with the quantity and quality of evidence of effectiveness can facilitate more individualized treatment plans for patients with this heterogeneous disorder.

Evaluation of harm in the pharmacotherapy of irritable bowel syndrome

OBJECTIVE

Current treatment options for irritable bowel syndrome are limited and often poorly studied. A select few drugs have been studied in irritable bowel syndrome, and the number needed to treat is frequently used to assess the relative efficacy of these treatments. However, side effects are an important consideration in the clinical decision on which particular treatment to use. This study examines trials of subjects with irritable bowel syndrome with diarrhea and constipation who are receiving a drug intervention deemed of merit by the American College of Gastroenterology task force and compares these therapies to examine the number needed to harm using a systematic review and meta-analysis approach.

METHODS

Potential studies of irritable bowel syndrome treatments were identified through a search of MEDLINE (1950 to April 2011), EMBASE (1980 to April 2011), the Cochrane central register of controlled trials, and the bibliography of recent meta-analyses. Clinical trials of pharmacotherapy for irritable bowel syndrome were eligible for inclusion only if a description of adverse events and the number of patients who discontinued treatment because of adverse events were reported. The relative risk of experiencing an adverse event requiring discontinuation of treatment was used to determine the number needed to harm. In addition, the number and severity of adverse events were summarized.

RESULTS

Twenty-six clinical trials (4 with selective serotonin reuptake inhibitors, 3 with lubiprostone, 6 with tricyclic antidepressants, 8 with alosetron, and 5 with rifaximin) were included. Lubiprostone was safe with insignificant harm in one combined phase III trial. Selective serotonin reuptake inhibitors did not have enough data for a reliable meta-analysis of harm but seemed to be safe. More rigorous data were available for tricyclic antidepressants, alosetron, and rifaximin; the numbers needed to harm were 18.3, 19.4, and 8971, respectively, and the numbers needed to treat were 8, 7.5, and 10.6, respectively. For tricyclic antidepressant and alosetron, an adverse event resulting in discontinuation of the study medication occurred for every 2.3 and 2.6 patients who benefited from a drug, respectively. For rifaximin, this number was 846 patients. In addition, adverse events were more common with tricyclic antidepressants and alosetron.

CONCLUSION

In irritable bowel syndrome with diarrhea, tricyclic antidepressants and alosetron are associated with a significant number needed to harm compared with rifaximin. Apart from lubiprostone, treatment of irritable bowel syndrome with constipation is limited to small studies (with poor descriptions of side effects), although lubiprostone and selective serotonin reuptake inhibitors appear safe.

Targeted therapies for diarrhea-predominant irritable bowel syndrome

Irritable bowel syndrome (IBS) causes gastrointestinal symptoms such as abdominal pain, bloating, and bowel pattern abnormalities, which compromise patients' daily functioning. Common therapies address one or two IBS symptoms, while others offer wider symptom control, presumably by targeting pathophysiologic mechanisms of IBS. The aim of this targeted literature review was to capture clinical trial reports of agents receiving the highest recommendation (Grade 1) for treatment of IBS from the 2009 American College of Gastroenterology IBS Task Force, with an emphasis on diarrhea-predominant IBS. Literature searches in PubMed captured articles detailing randomized placebo-controlled trials in IBS/diarrhea-predominant IBS for agents receiving Grade I (strong) 2009 American College of Gastroenterology IBS Task Force recommendations: tricyclic antidepressants, nonabsorbable antibiotics, and the 5-HT(3) receptor antagonist alosetron. Studies specific for constipation-predominant IBS were excluded. Tricyclic antidepressants appear to improve global IBS symptoms but have variable effects on abdominal pain and uncertain tolerability; effects on stool consistency, frequency, and urgency were not adequately assessed. Nonabsorbable antibiotics show positive effects on global symptoms, abdominal pain, bloating, and stool consistency but may be most efficacious in patients with altered intestinal microbiota. Alosetron improves global symptoms and abdominal pain and normalizes bowel irregularities, including stool frequency, consistency, and fecal urgency. Both the nonabsorbable antibiotic rifaximin and the 5-HT(3) receptor antagonist alosetron improve quality of life. Targeted therapies provide more complete relief of IBS symptoms than conventional agents. Familiarization with the quantity and quality of evidence of effectiveness can facilitate more individualized treatment plans for patients with this heterogeneous disorder.