A review of irritable bowel syndrome and an update on therapeutic approaches

Gastroesophageal reflux disease, functional dyspepsia and irritable bowel syndrome: common overlapping gastrointestinal disorders

Several studies have indicated an overlap between gastroesophageal reflux disease (GERD) and various functional gastrointestinal disorders (FGIDs). The overlapping conditions reported have mainly been functional dyspepsia (FD) and irritable bowel syndrome (IBS). The available literature is frequently based on symptomatic questionnaires or endoscopic procedures to diagnose GERD. Rarely, among patients with heartburn, pathophysiological evaluations have been considered to differentiate those with proven GERD from those without. Moreover, both GERD and IBS or FD showed enormous heterogeneity in terms of the criteria and diagnostic procedures used. The GERD-IBS overlap ranges from 3-79% in questionnaire-based studies and from 10-74% when GERD has been diagnosed endoscopically. The prevalence of functional dyspepsia (after normal upper endoscopy) is 12-15% and an overlap with GERD has been reported frequently. Only a few studies have considered a potential overlap between functional heartburn (FH) and IBS using a 24-h pH-metry or impedance-pH evaluation. Similar data has been reported for an overlap between FH and FD. Recently, a revision of the Rome criteria for esophageal FGIDs identified both FH and hypersensitive esophagus (HE) as potential functional esophageal disorders. This might increase the potential overlap between different FGIDs, with FH and HE rather than with GERD. The aim of the present review article was to appraise and discuss the current evidence supporting the possible concomitance of GERD with IBS and FD in the same patients and to evaluate how various GERD treatments could impact on the quality of life of these patients.

Differences of microbiota in small bowel and faeces between irritable bowel syndrome patients and healthy subjects

OBJECTIVE

Several studies suggested that colonic microbiota have impacts on irritable bowel syndrome (IBS) patients. However, the knowledge about the association of small intestine (SI) microbiota with IBS is limited. We aimed to investigate the gut microbiota composition of SI and stool in IBS patients.

MATERIALS AND METHODS

Biopsies of jejunum mucosa by balloon-assisted enteroscopy and faecal samples from 28 IBS patients and 19 healthy controls were analysed by next-generation sequencing method.

RESULTS

The three major phyla in SI microbiota of case/control groups were Proteobacteria (32.8/47.7%), Bacteroidetes (25.2/15.3%), and Firmicutes (19.8/11.2%), and those of stool were Bacteroidetes (41.3/45.8%), Firmicutes (40.7/38.2%), and Proteobacteria (15.4/7.1%). Analysis based on the family level, IBS patients had a higher proportion of Veillonellaceae (mean proportion 6.49% versus 2.68%, p = 0.046) in stool than controls. Prevotellaceae was more abundant in IBS patients than in control group (14.27% versus 6.13%, p = 0.023), while Mycobacteriaceae (0.06% versus 0.17%, p = 0.024) and Neisseriaceae (6.40% versus 8.94%, p = 0.038) was less abundant in IBS patients' jejunal mucosa than those in controls. This less abundant jejunal Neisseriaceae was associated with more severe IBS (p = 0.03). The ratio of Firmicutes to Bacteroidetes in the stool of IBS-diarrhoea type patients was approximately three-fold higher, and the ratio of Firmicutes to Actinobacter in SI of IBS-mixed type patients was about nine-fold higher than healthy subjects.

CONCLUSION

Higher abundance of colonic Veillonellaceae and SI Prevotellaceae, and lower amount of oral cavity normal flora in proximal SI were found in IBS patients. We may manipulate these bacteria in IBS patients in future studies (ClinicalTrial.gov Number NCT01679730).

Metabolic and toxicological considerations for the latest drugs used to treat irritable bowel syndrome

INTRODUCTION

The high prevalence of irritable bowel syndrome (IBS), a chronic gastrointestinal (GI) disorder, its lack of satisfactory effective drugs and its complicated pathophysiology lead to the demand of new therapeutic agents. During a new drug development process, the pharmacokinetic profiling is of a great considerable importance comparable to drug's efficacy. This involves the drug's absorption, distribution, metabolism and excretion, all of which are crucial to its usefulness. In addition, the toxicological profile and possible adverse reactions of the drug should be identified. Also its interactions should be identified at different phases of trials. Several pharmacokinetic studies are carried out to achieve drugs with the best absorption and bioavailability and the least adverse effects and lowest toxicity.

AREAS COVERED

To make an update on new clinically introduced drugs for IBS and their dynamics and kinetics data, the present systematic review was accomplished. All relevant bibliographic databases were searched from the year 2003 up to May 2012 to identify all clinical trials that evaluated the potential efficacy of a novel agent in IBS.

EXPERT OPINION

Some evaluated drugs, such as ramosetron (5-HT3 antagonist) and pexacerfont (CRF1 receptor antagonist), have shown some benefits in diarrhea-predominant IBS (D-IBS), while, prucalopride and mosapride (5-HT4 agonist) with prokinetic effect were found useful in constipation-predominant IBS (C-IBS). Besides, dexloxiglumide, lubiprostone and linaclotide have shown beneficial effects in C-IBS patients. Melatonin regulates GI tract motility and, asimadoline, gabapentin and pregabalin show reduction of pain threshold and visceral hypersensitivity. Glucagon-like peptide analog, calcium-channel blockers and neurokinin receptor antagonists have shown benefits in pain attacks. More time is required to indicate both efficacy and safety in long-term treatment due to multifactorial pathophysiology, variations in individual responses and insufficient assessment methods, which limit the right decision-making process about the efficacy and tolerability of these new drugs.

Treatment of irritable bowel syndrome

WHAT IS KNOWN AND OBJECTIVE

The complexity and diversity of irritable bowel syndrome's (IBS) presentation make treatment difficult. Although there are reviews and guidelines for treating IBS, they focus on the efficacy of medications for IBS symptoms using high-priority endpoints, leaving those of lower priority largely unreported. Therefore, the aim of this review is to provide a comprehensive evidence-based review of the efficacy of medications to treat IBS symptoms, reported by IBS subtype, including secondary symptom endpoints that are often underreported.

METHODS

A review of PubMed for articles published through December 2009 using the keywords: 'irritable bowel syndrome', 'therapeutics', 'antidiarrhoeals', 'laxatives', 'loperamide', 'dietary fibre', 'psyllium', 'calcium polycarbophil', 'bulking agents', 'lubiprostone', 'antidepressant agents, tricyclics' and its representative entities, 'serotonin reuptake inhibitors' and its representative entities, 'dicyclomine', hyoscyamine', 'peppermint oil', 'parasympatholytics' and its representative entities, 'rifaximin', 'pregabalin', 'gabapentin', 'clonidine', 'octreotide', 'atropine' and 'probiotics' is provided. Placebo-controlled trials were evaluated for the strength of evidence supporting the efficacy of each medication for explicit IBS symptoms. The efficacy of each medication for the symptoms of abdominal pain, bloating, stool form, mucus, urgency, feeling of incomplete evacuation, flatulence, frequency, or borborgymi and overall symptoms are reported by IBS subtype.

RESULTS AND DISCUSSION

The literature search identified 58 placebo-controlled trials of the efficacy of medications for treating IBS symptoms, which were critically evaluated and reported. The available studies suggest improvement in various IBS symptoms with loperamide, fibre supplements, lubiprostone, tricyclic antidepressants (TCAs), selective serotonin receptor inhibitors (SSRIs), antispasmotics, rifaximin, pregabalin, gabapentin, clonidine, octreotide and probiotic treatments.

WHAT IS NEW AND CONCLUSION

This review is the first to compile the available evidence on the efficacy of the various pharmacological treatments for IBS on the basis of IBS subtype and specific symptoms. This evidence is limited and more well-designed studies are required to better inform therapeutic decision-making in the management of this difficult syndrome.