Introduction: Diarrhea-predominant irritable bowel syndrome (IBS-D) affects about one-third of patients with IBS, which is observed in about 12% of people across five continents. The ultimate goal in this field is to identify the underlying cause of symptoms in order to individualize education of the patient, and to provide optimal treatment of this highly prevalent condition. Areas covered: This review addresses the pharmacological treatments for IBS-D under three categories: drugs for IBS-D (i.e., the 5-HT3 antagonist, alosetron); drugs approved for other indications that are used in IBS-D (e.g., opioid agonists; other 5-HT3 antagonists; serotonergic psychoactive agents; bile acid binders; 5-ASA compounds; probiotics and non-absorbable antibiotics); as well as development of drugs that are likely to impact the management of IBS-D in the future (e.g., drug absorbents; TPH1 inhibitors; mast cell stabilizers; centrally acting benzodiazepines). The final section addresses key findings: regulatory roadblocks; weaknesses in the current research in this field so far and opportunities to address unmet needs including restoration of normal intestinal barrier function or permeability, and suppression within the intestines of local immune activation that is thought to trigger abnormal motor, sensory and secretory functions in IBS-D. Expert opinion: While symptomatic treatment of diarrhea is effective, there is a need for new treatments for the IBS-D complex. Greater understanding of the mechanisms in IBS-D has led to promising approaches to develop more efficacious therapies.

Irritable bowel syndrome (IBS) is a functional bowel disorder characterized by abdominal pain, discomfort, and altered bowel habits, which have a significant impact on quality of life for approximately 10-20% of the population. IBS can be divided into three main types IBS-D (diarrhea predominant), IBS-C (constipation predominant), and mixed or alternating IBS. 5-HT(3) receptor antagonism has proved to be an efficacious treatment option for IBS-D. For example, alosetron displays efficacy in the treatment of multiple symptoms, including abdominal pain, discomfort, urgency, stool frequency and consistency. However, significant constipation occurred in approximately 25% of patients, leading to withdrawal of up to 10% of patients in clinical trials. Targeting compounds with partial agonist activity at the 5-HT(3) receptor represents a mechanistic departure from the classic 5-HT(3) receptor antagonist approach and should result in agents that are applicable to a broader array of IBS patient populations. Attenuation of the activity of the ion channel without completely abolishing its function may control or normalize bowel function without leading to a total block associated with severe constipation. We have identified a new class of selective, orally active 5-HT(3) receptor ligands with high 5-HT(3) receptor affinity and low partial agonist activity currently in preclinical development that should offer a significant advantage over existing therapies.

Irritable bowel syndrome is defined as abdominal discomfort or pain associated with altered bowel habits for at least three days per month in the previous three months, with the absence of organic disease. In North America, the prevalence of irritable bowel syndrome is 5 to 10 percent with peak prevalence from 20 to 39 years of age. Abdominal pain is the most common symptom and often is described as a cramping sensation. The absence of abdominal pain essentially excludes irritable bowel syndrome. Other common symptoms include diarrhea, constipation, or alternating diarrhea and constipation. The goals of treatment are symptom relief and improved quality of life. Exercise, antibiotics, antispasmodics, peppermint oil, and probiotics appear to improve symptoms. Over-the-counter laxatives and antidiarrheals may improve stool frequency but not pain. Treatment with antidepressants and psychological therapies are also effective for improving symptoms compared with usual care. Lubiprostone is effective for the treatment of constipation-predominant irritable bowel syndrome, and alosetron (restrictions for use apply in the United States) and tegaserod (available only for emergency use in the United States) are approved for patients with severe symptoms in whom conventional therapy has been ineffective.

Utilities of pertinent clinical outcomes are crucial variables for assessing the benefits and risks of drugs, but numerical data on utilities may be unreliable or altogether missing. We propose a method to incorporate qualitative information into a probabilistic decision analysis framework for quantitative benefit-risk assessment.To investigate whether conclusive results can be obtained when the only source of discriminating information on utilities is widely agreed upon qualitative relations, for example, ''sepsis is worse than transient headache'' or ''alleviation of disease is better without than with complications.''We used the structure and probabilities of 3 published models that were originally evaluated based on the standard metric of quality-adjusted life years (QALYs): terfenadine versus chlorpheniramine for the treatment of allergic rhinitis, MCV4 vaccination against meningococcal disease, and alosetron for irritable bowel syndrome. For each model, we identified clinically straightforward qualitative relations among the outcomes. Using Monte Carlo simulations, the resulting utility distributions were then combined with the previously specified probabilities, and the rate of preference in terms of expected utility was determined for each alternative.Our approach conclusively favored MCV4 vaccination, and it was concordant with the QALY assessments for the MCV4 and terfenadine versus chlorpheniramine case studies. For alosetron, we found a possible unfavorable benefit-risk balance for highly risk-averse patients not identified in the original analysis.Incorporation of widely agreed upon qualitative information into quantitative benefit-risk assessment can provide for conclusive results. The methods presented should prove useful in both population and individual-level assessments, especially when numerical utility data are missing or unreliable, and constraints on time or money preclude its collection.

TAK-480, 4-(difluoromethoxy)-N-((1R,2S)-2-(((3aR,4R,9bR)-4-(methoxymethyl)-2, 3,3a,4,5,9b-hexahydro-1H-pyrrolo[3,2-c]quinolin-1-yl)carbonyl)cyclohexyl)benzamide, is a novel tachykinin NK(2)-receptor antagonist. In this study, we investigated its antagonistic activity and efficacy in animal models of visceral hypersensitivity and stimulated bowel function which have been implicated to underlie the symptoms in irritable bowel syndrome (IBS). TAK-480 showed potent binding affinity for human NK(2) receptors with a marked species difference and a 10,000-fold selectivity versus NK(1) and NK(3) receptors. TAK-480 dose-dependently antagonized colonic contractions induced by administration of the NK(2) receptor-selective agonist beta-Ala(8)-NKA(4-10) (βA-NKA) in anesthetized rabbits. In a rabbit model of intracolonic zymosan-induced visceral hypersensitivity, TAK-480 markedly inhibited the visceromotor response to colorectal distension, in contrast to the moderate inhibition by the serotonin 5-HT(3)-receptor antagonist alosetron. In addition, TAK-480 suppressed ricinoleic acid-induced defecation without affecting spontaneous defecation in guinea pigs, whereas alosetron suppressed both. Furthermore, TAK-480 inhibited smooth muscle contractions produced by natural tachykinins (substance P, neurokinin A, and neurokinin B) as well as βA-NKA in an isolated human colon. In conclusion, the novel NK(2)-receptor antagonist TAK-480 improved visceral hypersensitivity and accelerated defecation without causing constipation in experimental animals. Furthermore, the potent functional blockade of NK(2) receptors in human colon might suggest the potential effectiveness of TAK-480 in IBS patients.

Patients with irritable bowel syndrome with diarrhoea (IBS-D) experience restriction in daily activities and decreased health-related quality of life (QOL).To investigate effects of alosetron on patient-reported health-related QOL, satisfaction and productivity in women with severe IBS-D.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.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.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.

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.

In drug trials involving subjects with irritable bowel syndrome (IBS), the placebo effect seems to be very important. However, events even before starting the study may also impact patient expectations. In this study, we utilized consent language from prior studies of diarrhea predominant IBS (D-IBS) drug trials to determine whether the knowledge imparted during this process affects the response to different therapies.Consecutive IBS subjects who met the Rome III criteria for IBS were enrolled. Patients were presented with a mock trial and randomized to 1 of 3 questionnaires with consent using similar language from consent forms of 3 drugs used in D-IBS: desipramine, alosetron, and rifaximin. Demographics, IBS symptoms using visual analog scale, and percent improvement needed for patients to report adequate relief of IBS from theoretically taking their assigned drug was asked. Data were expressed as mean ± SE.Subjects who were anticipating rifaximin had the highest expectation of improvement to determine adequate relief of 87.3 ± 10.9% compared with 73.4 ± 18.0% for desipramine (P<0.01) and 76.8 ± 20% for alosetron (P=0.049). There was no major difference in expectation of response from any medication to satisfy adequate relief on the basis of a belief that IBS is psychologic or organic in origin. In addition, sex and previous use of a drug did not influence the expectation of adequate relief.Benefits of drugs in D-IBS drug trials have the potential to be influenced by preconceived notions derived from familiarity of drug class and the consent process even before the study begins which we refer to as the "pre-cebo" effect. The higher pre-cebo effect for rifaximin may be an obstacle to successful treatment effect during drug trials compared with drugs such as desipramine. The pre-cebo effect may need to be taken into account when formulating consent forms for IBS study.

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.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.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.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.