Selective 5-hydroxytryptamine antagonism: a role in irritable bowel syndrome and functional dyspepsia?

Background: Abnormalities of gut motility and visceral pain perception are both thought to be involved in the pathogenesis of irritable bowel syndrome and may be susceptible to modulation by drugs affecting the various 5-HT receptor subtypes. The aim of this study was to investigate the therapeutic potential of a 5-HT₃ antagonist in irritable bowel syndrome.
Methods: Fifty patients with irritable bowel syndrome were treated with ondansetron, a highly selective 5-HT₃ antagonist, in a double-blind, placebo-controlled cross-over study. In addition to assessing its effect on the classical symptoms of irritable bowel syndrome (abdominal pain, distension and disordered bowel habit) its effect on symptoms often seen in irritable bowel syndrome, but more commonly associated with functional dyspepsia, was also examined.
Results: Ondansetron reduced bowel frequency ( P =0.035) and improved stool consistency ( P =0.002) in diarrhoea predominant irritable bowel syndrome and did not cause a deterioration of bowel habit in constipation predominant subjects. No statistically significant improvement was seen for abdominal pain or distension, although those patients who did respond were approximately twice as likely to be taking ondansetron than placebo. It was also found that ondansetron significantly improved the upper gastrointestinal symptoms of post-prandial epigastric discomfort ( P =0.008), flatulence ( P =0.022) and heartburn ( P =0.003).
Conclusion: The results of this study justify evaluation of the therapeutic potential of selective 5-HT antagonists in both functional dyspepsia and irritable bowel syndrome.     

Review article: gender-related differences in functional gastrointestinal disorders

Many functional gastrointestinal disorders and other chronic visceral pain disorders such as interstitial cystitis and chronic pelvic pain are more common in women than in men. In irritable bowel syndrome (IBS) there is a 2 : 1 female to male ratio in prevalence of symptoms in community samples. Female irritable bowel syndrome patients are more likely to be constipated, complain of abdominal distension and of certain extracolonic symptoms.
While animal studies have clearly demonstrated gender-related differences in pain perception and antinociceptive mechanisms, unequivocal evidence for gender-related differences in human pain perception or modulation has only been provided recently. Gender-related differences may be related to constant differences in the physiology of pain perception, such as structural or functional differences in the visceral afferent pathways involved in pain transmission or modulation, and/or they may be related to fluctuations in female sex hormones.
Preliminary evidence suggests that female irritable bowel syndrome patients show specific perceptual alterations in regards to rectosigmoid balloon distension and that they show differences in regional brain activation measured by positron emission tomography. This preliminary evidence suggests that gender-related differences in symptoms and in the perceptual responses to visceral stimuli exist in IBS patients and can be detected using specific stimulation paradigms and neuroimaging techniques.     

Anti-hyperalgesic effect of octreotide in patients with irritable bowel syndrome

BACKGROUND: Octreotide has been found to be beneficial in the treatment of chronic pain, although the mechanisms underlying its therapeutic effect are incompletely understood. AIMS: To assess the effect of octreotide on perceptual responses to rectal distension in irritable bowel syndrome patients and healthy controls at baseline and following the experimental induction of rectal hyperalgesia. METHODS: In study 1, rectal perception thresholds for discomfort were determined in seven irritable bowel syndrome patients and eight healthy controls on three separate days using a computer-controlled barostat. Subjects received saline, low-dose and high-dose octreotide in a random double-blind fashion. In study 2, perceptual responses to rectal distension were obtained in nine irritable bowel syndrome patients and seven controls before and after repetitive high-pressure mechanical sigmoid stimulation. RESULTS: Octreotide increased the discomfort thresholds in irritable bowel syndrome patients, but not in controls, without changing rectal compliance. Repetitive sigmoid stimulation resulted in decreased rectal discomfort thresholds in the patient group only. In irritable bowel syndrome patients, octreotide prevented the sensitizing effect of repetitive sigmoid stimulation on rectal discomfort thresholds. CONCLUSIONS: Octreotide effectively increased discomfort thresholds in irritable bowel syndrome patients, but not in controls, at baseline and during experimentally induced rectal hyperalgesia. These findings suggest that octreotide exerts primarily an anti-hyperalgesic rather than analgesic effect on visceral perception.     

Clinical trial: renzapride therapy for constipation-predominant irritable bowel syndrome--multicentre, randomized, placebo-controlled, double-blind study in primary healthcare setting

Background  Relatively few pharmacological treatment options are available for treating patients with irritable bowel syndrome. New and effective medicines are urgently required.
Aim  To identify an appropriate dosage of renzapride (a 5-HT₄ receptor full agonist/5-HT₃ receptor antagonist) to treat abdominal pain/discomfort in patients with constipation-predominant irritable bowel syndrome.
Methods  In this randomized, placebo-controlled, phase IIb study in the primary care setting, men and women were randomized to placebo or renzapride (1, 2 or 4 mg/day) for 12 weeks. The primary outcome measure was patient self-assessed relief of abdominal pain/discomfort during weeks 5–12. Secondary efficacy measures included patients' assessment of their bowel habits, stool consistency and quality of life.
Results  Although there were no statistically significant differences between renzapride and placebo for relief from abdominal pain/discomfort, responder rates in the renzapride treatment groups increased dose dependently, with the 4 mg/day group being consistently numerically greater than placebo. Importantly, a larger numerical treatment difference vs. placebo was observed in women (8% and 12% respectively). Statistically significant improvements in bowel movement frequency and stool consistency were observed in the 4 mg/day group relative to placebo. Renzapride was well tolerated at all doses.
Conclusions  This study confirms the gastrointestinal prokinetic effects of renzparide. The data also suggested a potentially beneficial effect on abdominal pain/discomfort in women with constipation-predominant irritable bowel syndrome.     

Irritable bowel syndrome in the United States: prevalence, symptom patterns and impact

BACKGROUND: The impact of irritable bowel syndrome, a gastrointestinal motility disorder, is underestimated and poorly quantified, as clinicians may see only a minority of sufferers. AIM: To determine the prevalence, symptom patterns and impact of irritable bowel syndrome in the US. METHODS: This two-phase community survey used quota sampling and random-digit telephone dialing (screening interview) to identify individuals with medically diagnosed irritable bowel syndrome or individuals not formally diagnosed, but fulfilling irritable bowel syndrome diagnostic criteria (Manning, Rome I or II). Information on irritable bowel syndrome symptoms, general health status, lifestyle and impact of symptoms on individuals' lives was collected using in-depth follow-up interviews. Data were also collected for healthy controls identified in the screening interviews. RESULTS: The total prevalence of irritable bowel syndrome in 5009 screening interviews was 14.1% (medically diagnosed: 3.3%; undiagnosed, but meeting irritable bowel syndrome criteria: 10.8%). Abdominal pain/discomfort was the most common symptom prompting consultation. Most sufferers (74% medically diagnosed; 63% undiagnosed) reported alternating constipation and diarrhoea. Previously diagnosed gastrointestinal disorders occurred more often in sufferers than non-sufferers. Irritable bowel syndrome sufferers had more days off work (6.4 vs. 3.0) and days in bed, and reduced activities to a greater extent than non-sufferers. CONCLUSIONS: Most (76.6%) irritable bowel syndrome sufferers in the US are undiagnosed. Irritable bowel syndrome has a substantial impact on sufferers' well-being and health, with considerable socioeconomic consequences.     

Oesophageal hypersensitivity is associated with features of psychiatric disorders and the irritable bowel syndrome

BACKGROUND: Twenty per cent of patients with heartburn do not respond to proton pump inhibitors (PPIs). Many have normal oesophageal acid exposure. We hypothesized that such PPI non-responders have heightened oesophageal sensation, and that oesophageal hypersensitivity is associated with psychiatric features including somatization and anxiety. AIM: To compare oesophageal sensation in subjects with heartburn categorized by response to PPI, and to correlate oesophageal sensation with psychiatric features. METHODS: Twenty-one PPI responders, nine PPI non-responders and 20 healthy volunteers completed questionnaires of psychiatric disorders and gastrointestinal symptoms. Subjects underwent oesophageal sensory testing with acid perfusion and balloon distension. RESULTS: Healthy volunteers displayed higher thresholds for sensation and discomfort from balloon distension than heartburn subjects (sensation P = 0.04, discomfort P = 0.14). Psychiatric disorders were associated with increased intensity of sensation (P = 0.02) and discomfort from acid (P = 0.01). Somatization was associated with increased discomfort from balloon distension (P = 0.006). Features of irritable bowel syndrome were associated with increased sensation and discomfort. CONCLUSIONS: Heartburn subjects tend to have heightened oesophageal sensation, suggesting that oesophageal hypersensitivity may persist despite therapy with PPI. Oesophageal hypersensitivity is associated with features of psychiatric disease and with the irritable bowel syndrome, which might partly explain the aetiology of heartburn symptoms that are refractory to PPI.     

Clinical trial: phase 2 study of lubiprostone for irritable bowel syndrome with constipation

Background Analyses of a trial in constipated patients indicated that lubiprostone may be an effective treatment for irritable bowel syndrome with constipation. Aim To assess the efficacy and safety of three lubiprostone doses for irritable bowel syndrome with constipation. Methods 195 irritable bowel syndrome with constipation patients received daily doses of 16 [8 μg twice daily (b.d.)], 32 (16 μg b.d.) or 48 μg (24 μg b.d.) lubiprostone or placebo b.d. for 3 months. Gastrointestinal parameters were recorded in diaries daily by patients. Results After 1 month, lubiprostone showed significantly greater improvements in mean abdominal discomfort/pain scores vs. placebo (P = 0.023). After 2 months, all lubiprostone groups showed significantly greater improvements in mean abdominal discomfort/pain scores (P ≤ 0.039). After 3 months of treatment, the improvement in each lubiprostone arm was greater than placebo, but the test for trend was no longer significant. Treatment with lubiprostone showed significantly higher rates of gastrointestinal adverse events (P = 0.020), especially diarrhoea and nausea. Conclusion Lubiprostone significantly improved gastrointestinal symptoms of irritable bowel syndrome with constipation at all doses. Higher doses of lubiprostone, especially the 48 μg/day group, were associated with more gastrointestinal adverse events. From these data, the 16 μg/day dose demonstrated the optimal combination of efficacy and safety. These results warrant further study of lubiprostone for treatment of irritable bowel syndrome with constipation patients.     

Gabapentin reduces rectal mechanosensitivity and increases rectal compliance in patients with diarrhoea-predominant irritable bowel syndrome

BACKGROUND: Gabapentin has been shown to reduce elements of central sensitization in human experimental hyperalgesia. It remains uninvestigated whether gabapentin has beneficial effects for irritable bowel syndrome associated with visceral hypersensitivity. AIMS: To evaluate the effects of gabapentin on sensory and motor function of the rectum in patients with diarrhoea-predominant irritable bowel syndrome. METHODS: Forty patients with diarrhoea-predominant irritable bowel syndrome completed this randomized, double-blind, placebo-controlled, parallel-grouped study. All patients received a barostat study and were subsequently randomized for 5-day treatment with gabapentin 300 mg/day and then 600 mg/day or placebo. On day 6, after subjects had their morning dose, the barostat experiment was repeated. RESULTS: The threshold pressures for bloating, discomfort and pain significantly increased after gabapentin, but not after placebo. Significant increase in the pressure and corresponding wall tension inducing discomfort or pain were observed in the gabapentin group, but not in the placebo group. Rectal compliance significantly increased after gabapentin, but not after placebo. The postprandial increase of rectal tone was not affected by gabapentin. CONCLUSION: Our results show that gabapentin reduces rectal sensory thresholds through attenuating rectal sensitivity to distension and enhancing rectal compliance in diarrhoea-predominant irritable bowel syndrome patients. The clinical efficacy of this drug in irritable bowel syndrome patients warrants investigation.     

Relationship between symptoms and hypersensitivity to rectal distension in patients with irritable bowel syndrome

BACKGROUND: Visceral hypersensitivity is considered an important pathophysiological mechanism in irritable bowel syndrome, yet its relationship to symptoms is unclear. AIM: To detect possible associations between symptoms and the presence of hypersensitivity to rectal distension in patients with irritable bowel syndrome. METHODS: Ninety-two irritable bowel syndrome patients and 17 healthy volunteers underwent a rectal barostat study. The association between specific irritable bowel syndrome symptoms and the presence of hypersensitivity was examined using Area under the Receiver Operating Characteristic curves. RESULTS: Irritable bowel syndrome patients had significantly lower thresholds for discomfort/pain than healthy volunteers: 24 (18-30) and 30 (27-45) mmHg above minimal distending pressure, respectively. Forty-one patients (45%) showed hypersensitivity to rectal distension. Proportions of patients with different predominant bowel habits were similar in hypersensitive and normosensitive subgroups (diarrhoea predominant: 39 and 41%, respectively; alternating type: 27 and 28%, respectively; constipation predominant: 34 and 31%, respectively). Severe abdominal pain was more frequent in hypersensitive, compared with normosensitive patients (88% vs. 67%, P = 0.02), but none of the individual irritable bowel syndrome symptoms could accurately predict the presence of hypersensitivity, as assessed by Area under the Receiver Operating Characteristic curve analysis. CONCLUSIONS: Hypersensitive and normosensitive irritable bowel syndrome patients present with comparable, heterogeneous symptomatology. Therefore, selection based on clinical parameters is unlikely to discriminate individual irritable bowel syndrome patients with visceral hypersensitivity from those with normal visceral sensitivity.     

Impact of advertisement and clinic populations in symptoms and perception of irritable bowel syndrome

BACKGROUND: This study assessed the impact of recruitment on irritable bowel syndrome clinical trials, by determining whether irritable bowel syndrome patients recruited from advertisement or a specialty clinic differ in clinical and physiologic measures. METHODS: We prospectively surveyed 657 irritable bowel syndrome patients who either: (i) were referred from a functional bowel disease clinic (52%); or (ii) responded to advertisement for clinical trials (48%), using questionnaires about bowel and psychological symptoms, and quality of life. In a subset of 42 irritable bowel syndrome patients (29 advertisement and 15 clinic patients), rectal discomfort thresholds were measured before and after repetitive sigmoid stimulation. RESULTS: While the advertisement population more commonly consulted primary care physicians, the clinic population more commonly consulted gastroenterologists. The clinic population reported more prevalent and severe abdominal pain, and higher psychological symptom scores, while the advertisement population had greater quality of life. In the visceral perception studies, both subgroups were hypersensitive to rectal distension. CONCLUSION: Compared to the clinic population, the advertisement population had less severe abdominal pain and psychological symptoms, better quality of life but similar visceral perception. The differences in clinical self-reports may have consequences for enrolment of these different patient populations into clinical trials.     

Effect of asimadoline, a kappa opioid agonist, on pain induced by colonic distension in patients with irritable bowel syndrome

BACKGROUND: Visceral hypersensitivity plays a major role in irritable bowel syndrome pathophysiology. Opioid kappa receptors on afferent nerves may modulate it and be the target for new irritable bowel syndrome treatments. AIM: This study evaluated the effect of the kappa opioid agonist asimadoline on perception of colonic distension and colonic compliance in irritable bowel syndrome patients. METHOD: Twenty irritable bowel syndrome female patients (Rome II criteria; 40 +/- 13 years) and hypersensitivity to colonic distension (Pain threshold < or = 32 mmHg) were included in a randomized double-blind cross-over trial comparing the effect of a single oral dose of asimadoline 0.5 mg or placebo on sensory thresholds (defined as a constant and sustained sensation) elicited by left colon phasic distension (5 mmHg steps, 5 min) up to a sensation of abdominal pain. Colonic compliance was compared by the slope of the pressure-volume curves. RESULTS: On asimadoline, pain threshold (mean +/- s.d.) (29.8 +/- 7.2 mmHg) was higher than on placebo (26.3 +/- 7.8 mmHg), difference not statistically significant (P = 0.1756, ANOVA). Area under curve of pain intensity rated at each distension step was significantly lower on asimadoline (89.3 +/- 33.9, ANOVA) than on placebo (108.1 +/- 29.7) (P = 0.0411). Thresholds of perception of nonpainful distensions were not altered on asimadoline, as compared with placebo. Colonic compliance was not different on placebo and asimadoline. CONCLUSION: Asimadoline decreases overall perception of pain over a wide range of pressure distension of the colon in irritable bowel syndrome patients, without altering its compliance. These data suggest that further studies should explore the potential benefit of asimadoline in treatment of pain in irritable bowel syndrome patients.     

CRF1 receptors as a therapeutic target for irritable bowel syndrome

The characterization of the corticotropin-releasing factor (CRF) family of neuroendocrine regulatory peptides, the cloning and pharmacological characterization of two CRF receptor subtypes (CRF(1) and CRF(2)), and the development of selective CRF receptor antagonists provided new insight to unravel the mechanisms of stress and the potential involvement of the CRF system in different pathophysiological conditions, including functional gastrointestinal disorders, mainly irritable bowel syndrome (IBS), and psychopathologies such as anxiety/depression. Compelling pre-clinical data showed that brain CRF administration mimics acute stress-induced colonic responses and enhances colorectal distension-induced visceral pain in rats through CRF(1) receptors. Similarly, peripheral CRF reduced the pain threshold to colonic distension and increased colonic motility in humans and rodents. These observations mimic the manifestations of IBS, characterized by abdominal bloating/discomfort and altered bowel habits. Moreover, CRF-CRF(1) pathways have been implicated in the development of anxiety/depression. These psychopathologies, together with stressful life events, have high comorbidity with IBS, and are considered significant components of the disease. From these observations, CRF(1) receptors have been suggested as a target to treat IBS. Peripherally acting CRF(1) antagonists might directly improve IBS symptoms, as related to motility, secretion and immune response. On the other hand, central actions will be beneficial as to prevent the psychopathologies that co-exist with IBS and as a way to modulate the central processing of stress- and visceral pain-related signals. Here, we review the pre-clinical and clinical data supporting these assumptions, and address the efforts done at a pharmaceutical level to develop effective therapies targeting CRF(1) receptors for functional gastrointestinal disorders.     

Effect of long-term treatment with octreotide on rectal sensitivity in patients with non-constipated irritable bowel syndrome

BACKGROUND: Acute administration of octreotide reduces visceral perception and therefore has been suggested as potential treatment for irritable bowel syndrome. Whether prolonged treatment with octreotide also reduces visceral sensitivity and improves gastrointestinal symptoms remains, however, unknown. AIM: To investigate the effect of a slow release preparation of octreotide on rectal sensitivity and symptoms in irritable bowel syndrome patients. METHODS: Forty-six non-constipated irritable bowel syndrome patients (52% female, 19-63 years) participated. Before and after 8 weeks of treatment with octreotide (Sandostatin LAR 20 mg i.m.) or placebo, patients underwent a barostat study to assess the rectal sensitivity. During a 2-week run-in period and treatment, abdominal pain, defecation frequency, consistency and symptom relief were scored weekly. RESULTS: Octreotide, but not placebo, significantly increased the threshold for first sensation. Thresholds for urge to defecate and discomfort/pain and rectal compliance were not altered by either treatment. Octreotide improved stool consistency compared with placebo (loose stools after eight weeks: octreotide: 52%, placebo: 81%, P < 0.05). In contrast, abdominal pain and defecation frequency were not affected. CONCLUSIONS: Although the threshold of first rectal sensation increased and stool consistency improved, long-term treatment with octreotide, at least at the current dose used, has no visceral analgesic effect and fails to improve irritable bowel syndrome symptoms.     

Tegaserod: a serotonin 5-HT4 receptor agonist for treatment of constipation-predominant irritable bowel syndrome

Activation of serotonin 5-HT(4) receptors has been proposed as treatment for irritable bowel syndrome, a common, complex and distressing gastrointestinal disorder. Abnormal intestinal motility and sensitivity in irritable bowel syndrome patients can result in diarrhea, constipation, abdominal pain, bloating, headache and fatigue; these and other symptoms can lead to exacerbation of psychological stress, which may in turn induce further physiological abnormalities and patient discomfort. The serotonin agonist tegaserod binds with high affinity to 5-HT(4) receptors and has demonstrated potent pharmacological effects on the mid- and distal gut. Tegaserod has been safely employed in clinical trials where it has demonstrated efficacy in normalizing intestinal function, thereby improving irritable bowel syndrome symptoms.     

A randomized,double-blind,placebo-controlled trial of tegaserod in female patients suffering from irritable bowel syndrome with constipation

BACKGROUND: Irritable bowel syndrome is a common functional gastrointestinal disorder which affects up to 20% of the population, with a predominance in females. AIM: To evaluate the efficacy and safety of tegaserod in female patients with irritable bowel syndrome characterized by symptoms of abdominal pain/discomfort and constipation. METHODS: In a randomized, double-blind, multicentre study, 1519 women received either tegaserod, 6 mg b.d. (n = 767), or placebo (n = 752) for 12 weeks, preceded by a 4-week baseline period without treatment and followed by a 4-week open withdrawal period. The primary efficacy evaluation was the patient's symptomatic response as measured by the Subject's Global Assessment of Relief. Other efficacy variables included abdominal pain/discomfort, bowel habits and bloating. RESULTS: Tegaserod produced significant (P < 0.05) improvements in the Subject's Global Assessment of Relief and other efficacy variables. These improvements were seen within the first week, and were maintained throughout the treatment period. After withdrawal of treatment, the symptoms rapidly returned. Overall, tegaserod was well tolerated. Diarrhoea was the most frequent adverse event; however, this led to discontinuation in only 1.6% of tegaserod-treated patients. CONCLUSIONS: Tegaserod, 6 mg b.d., produced rapid and sustained improvement of symptoms in female irritable bowel syndrome patients and was well tolerated.     

Effect of a 5HT3-antagonist (ondansetron) on rectal sensitivity and compliance in health and the irritable bowel syndrome

In some patients with the irritable bowel syndrome, rectal urgency and discomfort are major clinical problems and, under experimental conditions, these symptoms are perceived at lesser volumes of rectal distension than they are in asymptomatic controls. Further, a 5-hydroxytryptamine type-3 receptor antagonist increased the threshold for rectal discomfort in irritable bowel syndrome. Our aims were, (a) to measure rectal sensation during isobaric distensions of the rectum, and (b) to test the effect of another selective 5HT₃ antagonist, ondansetron 0.15 mg/kg, on rectal sensitivity, colonic tone, rectal tone and manometric responses. Ten healthy volunteers and five patients with diarrhoea-predominant irritable bowel syndrome were studied. A multilumen barostatmanometric assembly was placed in the descending colon, and a second barostat balloon was positioned in the rectum. Tone in the wall of the colon and rectum was measured by the barostat balloon volume during a constant pressure clamp, while intraluminal pressures were recorded by manometry; perceived sensations were also recorded before and after the intravenous administration of ondansetron or placebo in blinded fashion. Rectal resistance to stretch was greater and rectal urgency was induced by lower distending pressures in irritable bowel syndrome, however, basal tone in the rectum was similar in health and irritable bowel syndrome. Ondansetron did not change rectal sensitivity (first sensation or urgency) or tone. Rectal distension did not alter tone in the descending colon or colonic manometry; ondansetron did not influence any index of colonic function. We conclude that in diarrhoea-predominant irritable bowel syndrome there is reduced rectal compliance and the rectum is abnormally sensitive to a pressure stimulus, but this is not altered by 5HT₃-blockade with ondansetron at the dose used.     

胃肠安丸对肠易激综合征治疗作用分析

胃肠安丸是一种复方中药制剂,常用以治疗腹泻,可有效消除腹痛、腹泻、腹胀、功能性消化不良等一系列胃肠不适的症状,西医称之为肠易激综合征（IBS）。胃肠安丸在发挥止泻作用的同时能够帮助机体恢复胃肠动力、调整胃肠运动节律、促进胃肠道消化吸收功能,从而治疗胃肠功能性障碍。该药组方合理,配伍精当,经临床验证疗效显著。针对肠易激综合征的病症特点深入分析了胃肠安丸在治疗腹泻病症中的配伍特点以及止泻作用机制,为该药的进一步研究奠定理论基础。     

New therapeutical approaches for treatment of irritable bowel syndrome

Irritable bowel syndrome is a common functional disorder of the gut. The cause is not known. Symptoms can be quite variable and include abdominal pain, bloating, and sometimes bouts of diarrhea and/or constipation. It causes a great deal of discomfort and distress, but it does not permanently harm the intestine and does not lead to a serious disease, such as cancer. There are numerous treatment options in functional gastrointestinal disorders acting peripherally by influencing motility and visceral sensitivity. However, older 5-HT4 receptor agonists had limited clinical success because they were associated with changes in the cardiac function. New generation 5-HT4 receptor agonists, 5-HT, antagonists or partial antagonists are promising approaches to treat gastrointestinal dysmotility, particularly colonic diseases. A further new approach is the activation of chloride cannels within the gastrointestinal wall by the prostaglandin E metabolite lubiprostone. In patients with chronic constipation, lubiprostone produced a bowel movement, with sustained improvement in frequency as well as other constipation symptoms. Ongoing clinical trials suggest that linaclotide, a first-in-class, 14-amino acid peptide guanylate cyclase C (GC-C) receptor agonist and intestinal secretagogue is also an effective treatment for chronic constipation. The pharmacological profile suggests that orally administered linaclotide may be capable of improving the abdominal symptoms and bowel habits of patients suffering from of constipation-predominant irritable bowel syndrome and chronic constipation. Data are emerging, but the efficacy and safety profile of these agents in the treatment irritable bowel disease appears encouraging. Further randomized controlled trials are warranted.     

A double-blind, randomized, placebo-controlled dose-ranging study to evaluate the efficacy of alosetron in the treatment of irritable bowel syndrome

BACKGROUND: Irritable bowel syndrome is a common gastrointestinal disorder characterized by abdominal pain and discomfort and altered bowel habit. Antagonism at the 5-HT3 receptor may be of benefit in the treatment of irritable bowel syndrome. AIMS: To evaluate the effect of 12 weeks of treatment with alosetron, a 5-HT3 receptor antagonist at doses of 0.1 mg b.d., 0.5 mg b.d. and 2 mg b.d. in irritable bowel syndrome patients. METHODS: A double-blind, placebo-controlled, parallel-group study with a 2-week screening and a 12-week treatment period was conducted. A total of 462 patients (335 female) recorded details of the severity of their abdominal pain, and bowel function daily on a diary card throughout the study. At monthly clinic visits patients recorded the severity of their abdominal pain/discomfort and diarrhoea on a visual analogue scale. RESULTS: In the total population and in the female subpopulation (but not in males) alosetron 2 mg b.d. significantly increased the proportion of pain-free days and decreased the visual analogue scale score for diarrhoea compared with placebo. Alosetron at doses of 0.5 mg b.d. and 2 mg b.d. led to a significant hardening of stool, and a reduction in stool frequency in the total population. CONCLUSION: Alosetron at a dose of 2 mg b.d. is an effective treatment for female patients with irritable bowel syndrome.     

Alosetron

Alosetron is a potent and highly selective serotonin 5-HT3 receptor antagonist which has been evaluated for the management of irritable bowel syndrome (IBS). It blocked the fast 5HT3-mediated depolarisation of guinea-pig myenteric and submucosal neurons in vitro, with half-maximal inhibition at approximately 55 nmol/L. Alosetron attenuated the visceral nociceptive effect of rectal distension in conscious or anaesthetised dogs. It increased the compliance of the colon to distension in patients with IBS and delayed colonic transit in patients with IBS or carcinoid diarrhoea and in healthy volunteers. A single dose of alosetron 4 mg increased in vivo fluid absorption in normal human small intestine. In clinical trials in patients with IBS, alosetron 1 mg twice daily was effective in relieving abdominal pain and discomfort. Alosetron was most effective in female patients and particularly in those with diarrhoea-predominant IBS. In patients with IBS and healthy volunteers who received alosetron, the most common adverse event was constipation.