Role of loperamide and placebo in management of irritable bowel syndrome (IBS)

Opioids and the gut: pharmacology and current clinical experience

This article reviews the pharmacology and physiology of opiate receptors and the current and potential uses of opioid agonists and antagonists in clinical gastroenterology. Mu-receptors are involved in motor and sensory functions, and their modulation is established for treatment of diarrhea. Mu-antagonists have potential to reverse endogenous (e.g., postoperative ileus) or iatrogenic dysmotility (e.g., opioid bowel dysfunction). Modulation of the function of kappa-receptors may be a novel approach to control visceral pain in functional gut disorders. Results of formal testing of novel opioid modulators are keenly awaited.

Inflammation as a basis for functional GI disorders

The term 'Functional diseases' implies symptoms arising from an organ without overt pathology. However this is more apparent than real since inflammation often leaves changes in nerves and mucosal function only apparent with specialised techniques. Acute onset functional dyspepsia accounts for around 1/5 of functional dyspepsia and is characterised by early satiety, nausea, vomiting and weight loss. Impaired postcibal fundal accommodation may underlie some of these symptoms. Post infectious gastroparesis is much rarer and is associated with markedly delayed gastric emptying and antral hypomotility. Approximately 1/10 of IBS cases describe a post infectious onset. Post infectious IBS is typically of the diarrhoea-predominant type. Post inflammatory functional diseases tend to be associated with less psychological abnormalities and have a better prognosis than other functional diseases. There are isolated anecdotal reports of symptom response to anti-inflammatory treatments but larger controlled trials are needed.

Pathophysiology as a basis for understanding symptom complexes and therapeutic targets

Sensorimotor disorders of the stomach, small intestine and colon have a limited repertoire of clinical manifestations, and there is the potential for more than one mechanism to lead to symptoms. In many recent clinical trial programs of novel agents in neurogastroenterology, the emphasis has been primarily on symptom assessment of broad groups of patients identified by the Rome criteria. Drugs of potential value have fallen by the wayside with this approach. We propose the current paradigm is partly to blame; physiological testing should provide the basis for identifying more homogeneous populations and therapeutic targets within functional bowel disease, and this applies to the upper and lower gut. Here we summarize the evidence that certain biomarkers can, in a limited fashion, be used to predict the success of an experimental medicine in common disorders of gastrointestinal function, including the irritable bowel syndrome and functional dyspepsia. Although the current evidence is limited and is most convincingly demonstrated with examples of transit measurements (for loperamide, alosetron, tegaserod and piboserod), we perceive this paradigm that studies using validated and responsive biomarkers have an important role to play in drug development.

Reassessing the Benefits and Risks of Alosetron

Functional gastrointestinal disorders such as the irritable bowel syndrome (IBS) cause substantial morbidity and a high amount of healthcare utilisation. However, no direct mortality can be attributed to functional disorders. Hence, drug treatment of IBS must not only be highly efficient to relieve clinical symptoms but also very safe for the long-term use in humans with such chronic disorders. Alosetron is a potent and highly selective serotonin 5-HT(3 )receptor antagonist that in large randomised controlled clinical trials has been shown to be clinically efficient in female patients with diarrhoea-predominant IBS. The efficacy data along with a low number of serious adverse effects in the preclinical and clinical trials suggested a favourable benefit/risk profile that led to US FDA approval of alosetron in early 2000. However, postmarketing experience has proven that several serious adverse effects, including death, occurred in the treated patient population, which resulted (for a time) in the withdrawal of alosetron from the US market by the producer (GlaxoSmithKline). In the meantime, both public pressure and the proposal of a careful postmarketing surveillance have led the FDA to re-approve alosetron to the US drug market under severe restrictions. These restrictions aim to ensure a safer use of the drug with a more favourable safety profile. Under these restrictions, however, it is not very likely that alosetron will become a major treatment option for many patients, but presumably the continued use of this first selective serotonin antagonist will open an avenue for the development of similar drugs with more favourable benefit/risk profiles in the near future.

Evaluation of drug treatment in irritable bowel syndrome

The irritable bowel syndrome (IBS) remains a therapeutic challenge in part because of the limited understanding of the pathophysiology. The placebo response rate varies in randomized controlled trials from 20 to 70%, and can persist for up to at least 1 year. It is contentious whether dietary fibre and bulking agents relieve the symptoms of IBS; constipation probably improves. Anticholinergic and antispasmodic agents are of questionable benefit in IBS despite positive meta-analyses of poor quality trials. A meta-analysis concluded that the tricyclic antidepressants were superior to placebo in IBS, although the individual trial results were variable. Selective serotonin reuptake inhibitors are of uncertain benefit. Laxatives are used for constipation but probably poorly control the IBS symptom complex. Loperamide is superior to placebo in improvement of diarrhoea but not abdominal pain in IBS. Tegaserod is a well- tolerated aminoguanidine indole derivative of serotonin that is a partial 5HT4-receptor agonist with prokinetic properties; a therapeutic gain over placebo of 5% to 15% has been observed in constipation-predominant IBS in females. Alosetron is a 5HT3-receptor antagonist that is efficacious in females with diarrhoea-predominant IBS, with a 12% to 17% therapeutic gain; the risk of ischaemic colitis is 1 in 350, with very severe constipation occurring in about 1 in 1000. Optimizing study design remains a challenge in IBS. New visceral analgesic and motility modifying agents, as well as anti-inflammatory agents are in trials, and hopefully additional efficacious therapeutic options for patients with IBS will soon emerge.

Clinical trial guidelines for pharmacological treatment of irritable bowel syndrome

Appropriate guidelines for clinical trials in irritable bowel syndrome are needed because of the inadequacy of previously performed trials, the use of new and more adequate patient definition, new emerging pathophysiological models and the unique requirements related to the assessment of treatment outcome that, in the absence of a biological marker, can rely only on the evaluation of clinical manifestations. This consensus report highlights the following points. (a) A 4-week period is considered to be adequate to assess drug efficacy for the control of symptoms. (b) For the cyclic and non-life-threatening nature of the disease, a long-term study of 4-6 months or more of active treatment to establish efficacy is considered to be inappropriate in the large majority of patients. (c) In the initial assessment phase of drug efficacy, the withdrawal effect of treatment can be ascertained during a follow-up period prolonged for a sufficient time (4-8 weeks) after stopping treatment. Subsequent trials with proper withdrawal phase design and duration can then ascertain the drug post-treatment benefit. (d) Considering the intermittent clinical manifestations of irritable bowel syndrome, designing trials with on-demand or repeated cycles of treatment could be envisaged. However, the lack of a definition of what constitutes an exacerbation is a major obstacle to the design of such trials. In the absence of an established gold standard, appropriately justified novel trial designs are welcome. (e) Patients eligible for inclusion should comply with the Rome II diagnostic criteria for irritable bowel syndrome. (f) The main efficacy outcome of the treatment should be based on one primary end-point. (g) The primary efficacy end-point could combine, in a global assessment, the key symptoms (abdominal pain, abdominal discomfort, bowel alterations) of irritable bowel syndrome or rate any single symptom for drugs considered to target specific symptoms. (h) A 50% improvement in the primary efficacy end-point seems to be a reasonable definition of a responder.

New approaches to the medical treatment of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common disorder with a worldwide distribution; it is characterized by abdominal pain and discomfort associated with an alteration of bowel function. The treatment approach for IBS depends on the patient's presenting symptoms at the time of diagnosis, and treatment is usually directed toward the predominant symptom. In this review we discuss the current approach to the treatment of IBS.

Pharmacotherapy for intestinal motor and sensory disorders

Motor disorders of the gastrointestinal tract are characterized by definable impairments of gut contractile function. Other conditions exhibit specific disturbances of visceral afferent and efferent activity, which may underlie selected symptom complexes. Medications in several classes have been developed to treat these disorders of gastrointestinal function. Prokinetic agents are effective therapies for ailments with reduced motor function, whereas antispasmodic drugs reduce symptoms in conditions with exaggerated pressure wave activity. Recently, medications designed to blunt transmission in visceral sensory pathways have been proposed for use in the functional bowel disorders. Finally, some patients may benefit from initiation of nonspecific therapies, which have no appreciable effect on gut motor or sensory function.

Postinfectious irritable bowel syndrome

A small but significant subgroup of patients with irritable bowel syndrome (IBS) report a sudden onset of their IBS symptoms after a bout of gastroenteritis. Population-based surveys show that although a history of neurotic and psychologic disorders, pain-related diseases, and gastroenteritis are all risk factors for developing IBS, gastroenteritis is the most potent. More toxigenic organisms increase the risk 11-fold, as does an initial illness lasting more than 3 weeks. Hypochondriasis and adverse life events double the risk for postinfective (PI)-IBS and may account for the increased proportion of women who develop this syndrome. PI-IBS is associated with modest increases in mucosal T lymphocytes and serotonin-containing enteroendocrine cells. Animal models and some preliminary human data suggest this leads to excessive serotonin release from the mucosa. Both the histologic changes and symptoms in humans may last for many years with only 40% recovering over a 6-year follow-up. Celiac disease, microscopic colitis, lactose intolerance, early stage Crohn's disease, and bile salt malabsorption should be excluded, as should colon cancer in those over the age of 45 years or in those with a positive family history. Treatment with Loperamide, low-fiber diets, and bile salt- binding therapy may help some patients. Serotonin antagonists are logical treatments but have yet to be evaluated.

Pharmacologic therapy for the irritable bowel syndrome

The management of the irritable bowel syndrome (IBS) remains unsatisfactory. For abdominal pain, antispasmodics are, at best, of only modest efficacy. Tricyclic antidepressants in low dose are useful (with the number needed to treat being three), but side effects and patient concerns regarding use of a centrally acting agent for depression remain limitations. Selective serotonin reuptake inhibitors are of uncertain efficacy in IBS. Opioid agonists, especially loperamide, are useful for diarrhea but not for pain in IBS; rebound constipation also remains a problem. Bile salt sequestering agents are not of established value in IBS but seem to be useful clinically in a small group of IBS patients with diarrhea. Aloestron, a 5HT(3) antagonist, should be reserved, if available, for women with severe diarrhea predominant IBS who have failed to respond to conventional therapy, and started at a low dose. Fiber and bulking agents may help constipation in some trials, but the evidence that they are efficacious in IBS is equivocal; they are frequently prescribed as first-line drugs for IBS regardless of the primary bowel disturbance but often increase bloating, gas, and pain. Laxatives are not of established value in IBS but are often taken by patients with constipation predominant IBS. Tegaserod, a partial 5HT(4) agonist, is now available in the United States and other countries for use in women with IBS whose primary bowel symptom is constipation; its efficacy in men and in those with alternating bowel habits is unknown. Probiotics are of uncertain efficacy. Chinese herbal medicine data are insufficient. Other new drugs in development include the cholecystokinin antagonists and novel visceral analgesics. Both current and potential therapies for IBS are reviewed in this article.

The irritable bowel syndrome

Symptoms of IBS are very prevalent. One quarter of symptomatic individuals present for medical care because of symptom severity and psychologic factors. The pathogenesis of IBS is multifactorial, involving abnormalities in the gut, immune system, enteric sensory and motor nerves, and the CNS. IBS is diagnosed by symptomatology according to the Rome criteria and the absence of alarm findings suggestive of organic disease. Minimal testing is advocated to confirm the diagnosis in patients presenting with typical symptoms. Therapy is based on the dominant symptom (IBS subtype). Therapeutic options include dietary modifications, counseling, medications, and psychologic treatments. Novel therapies are being investigated to correct potentially pathogenetic peripheral and CNS abnormalities in IBS.

Irritable bowel syndrome. Diagnosis is based on clinical criteria

Irritable bowel syndrome is one of several functional bowel disorders. As the data about this common syndrome increase, so does the understanding that it is a disorder with complex pathophysiologic factors. In this article, Drs Morgan and Robson provide the latest information about IBS and its diagnosis and outline a strategy for cost-effective treatment and improved quality of life for patients with this disorder.

Pregabalin (CI-1008) inhibits the trinitrobenzene sulfonic acid-induced chronic colonic allodynia in the rat

In human, digestive disorders are often associated with visceral pain. In these pathologies, visceral pain threshold is decreased indicating a visceral hypersensitivity. Pregabalin [CI-1008; S-(+)-3-isobutylgaba] presents antihyperalgesic actions in inflammatory somatic pain models. This study was designed to evaluate 1) the effect of injection of TNBS into the colon on visceral pain threshold, and 2) the antihyperalgesic effect of pregabalin on TNBS-induced chronic colonic allodynia. A significant decrease in the colonic pain threshold was observed in trinitrobenzene sulfonic acid (TNBS)-treated animals (17.8 +/- 1.27 versus 43.4 +/- 1.98 mm Hg). Pregabalin (30-200 mg/kg s.c.) and morphine (0.1-1 mg/kg s.c.) showed a dose-related inhibition of TNBS-induced colonic allodynia. Pregabalin did not inhibit the colonic inflammatory effect of TNBS. In normal conditions (control animals), morphine (0.3 mg/kg s.c.) significantly increased the colonic pain threshold, whereas pregabalin (200 mg/kg s.c.) did not modify the colonic pain threshold. Pregabalin suppressed the TNBS-induced colonic allodynia but did not modify the colonic threshold in normal conditions. The ability of pregabalin to block the chronic colonic allodynia indicates that it is effective in abnormal colonic hypersensitivity, suggesting a possible effect in chronic pain in irritable bowel syndrome.

Irritable Bowel Syndrome

Because treatment of irritable bowel syndrome (IBS) patients can be frustrating to the clinician and patient as well, the physician should strive to gain the patient's confidence with a concise, appropriate work-up and by offering reassurance and education that IBS is a functional disorder without significant long-term health risks. First-line treatment should be aimed at treating the most bothersome symptom. Tricyclic antidepressants are superior to placebo in reducing abdominal pain scores, as well as improving global symptom severity. Loperamide is superior to placebo in managing IBS-associated diarrhea. Whereas fiber has a role in treating constipation, its value for IBS or, specifically, in the relief of abdominal pain or diarrhea associated with IBS is controversial. Although certain antispasmodics have demonstrated superiority over placebo in managing abdominal pain, none of these agents are available in the United States. Probiotic therapy using Lactobacillus plantarum has demonstrated superiority to placebo in improving pain, regulating bowel habits, and decreasing flatulence. As studied in a recent placebo-controlled prospective study, Chinese herbal medicines significantly improved bowel symptom scores and global symptom profile, and reduced IBS-related quality of life impairment. Some of the most promising emerging therapies in IBS revolve around targeted pharmacotherapeutic modulation of serotonin receptors (ie, 5-HT3 and 5-HT4 subtypes), which are involved in sensory and motor functions of the gut. Other investigational agents that are also being explored include cholecystokinin antagonists, alpha2-adrenergic agonists (eg, clonidine), serotonin reuptake inhibitors (eg, citalopram), and neurokinin antagonists. IBS is best understood through the biopsychosocial paradigm, and therefore, its effective management requires a comprehensive multidisciplinary approach based on patient education and reassurance, enhanced by diet recommendations and lifestyle modifications, and complemented by pharmacotherapy and psychosocial intervention in more severe cases.

Clinical perspectives, mechanisms, diagnosis and management of irritable bowel syndrome

This consensus document reviews the current status of the epidemiology, social impact, patient quality of life, pathophysiology, diagnosis and treatment of irritable bowel syndrome. Current evidence suggests that two major mechanisms may interact in irritable bowel syndrome: altered gastrointestinal motility and increased sensitivity of the intestine. However, other factors, such as psychosocial factors, intake of food and prior infection, may contribute to its development. Management of patients is based on a positive diagnosis of the symptom complex, careful history and physical examination to exclude 'red flags' as risk factors for organic disease, and, if indicated, investigations to exclude other disorders. Therapeutic choices include dietary fibre for constipation, opioid agents for diarrhoea and low-dose antidepressants or infrequent use of antispasmodics for pain, although the evidence basis for efficacy is limited or in some cases absent. Psychotherapy and hypnotherapy are the subject of ongoing study. Treatment should be tailored to patient needs and fears. Novel therapies are emerging, and drugs acting on serotonin receptors have proven efficacy and a scientific rationale and, if approved, should be useful in the overall management of patients with irritable bowel syndrome. Patient and physician education, early identification of psychosocial issues and better therapies are important strategies to reduce the suffering and societal cost of irritable bowel syndrome.

Irritable bowel syndrome neuropharmacology. A review of approved and investigational compounds

Anticholinergics and prokinetics are mainstays of therapy for Irritable Bowel Syndrome (IBS) patients despite their limited efficacy and troublesome side-effect profile. The clinical limitations of these drugs are a result of their relative broad and nonspecific pharmacologic interaction with various receptors. Recent advances in gut physiology have led to the identification of various receptor targets that may play a pivotal role in the pathogenesis of IBS. Medicinal chemists searching for safe and effective IBS therapies are now developing compounds targeting many of these specific receptors. The latest generation of anticholinergics, such as zamifenacin, darifenacin, and YM-905, provide selective antagonism of the muscarinic type-3 receptor. Tegaserod, a selective 5-HT4 partial agonist, tested in multiple clinical trials, is effective in reducing the symptoms of abdominal pain, bloating, and constipation. Ezlopitant and nepadudant, selective antagonists for neurokinin receptors type 1 and type 2, respectively, show promise in reducing gut motility and pain. Loperamide, a mu (mu) opioid receptor agonist, is safe and effective for IBS patients with diarrhea (IBS-D) as the predominant bowel syndrome. Fedotozine, a kappa (kappa) opioid receptor agonist, has been tried as a visccral analgesic in various clinical trials with conflicting results. Alosetron, a 5-HT3 receptor antagonist, has demonstrated efficacy in IBS-D patients but incidents of ischemic colitis seen in post-marketing follow-up resulted its removal from the market. Compounds that target cholecystokinin. A, N-methyl-D-aspartate, alpha 2-adrenergic, and corticotropin-releasing factor receptors are also examined in this review.

Functional bowel disorders in inflammatory bowel disease

Patients with IBD in remission often have ongoing gastrointestinal symptoms that are related to active inflammation. It is now apparent that functional gastrointestinal disorders may overlap with IBD and increase morbidity and diminish the quality of life of patients. Recognition and treatment of functional symptoms that may be the result of IBD are crucial in the appropriate medical management of these patients.

Review article: the complexity of drug development for irritable bowel syndrome

Drug development for functional gastrointestinal disorders is complex. These conditions involve central and peripheral physiological changes, together with psychological factors. Methodological problems have included a poor appreciation of the physiological and psychological correlates of patients' symptoms, a lack of animal models of proven relevance, and safety issues. Government, patient pressure groups and the Internet can also influence a drug's success. Most recent interest has focused on the serotonin (5-HT) modifying drugs. Cisapride has been withdrawn in some countries because of concerns related to QT prolongation and cardiac arrhythmias. The 5-HT3 antagonists, developed to modify visceral sensation, have caused constipation; alosetron, also withdrawn, caused ischaemic colitis. The 5-HT4 agonists induce peristalsis; tegaserod and prucalopride, both delayed in their development due to issues of safety and efficacy, benefit patients with 'constipation-predominant' irritable bowel syndrome or idiopathic constipation. 5-HT1 agonists improve impaired gastric accommodation and symptoms in patients with functional dyspepsia. Antidepressants also affect serotonin metabolism. Previous examples of success in this area involved drugs targeted at peripheral receptors mediating motor function or secretion. Modification of sensory function is a much more challenging objective. The experience with serotonin modifying drugs has been mixed, and some important lessons are there to be learnt.

Serotoninergic neuroenteric modulators

Irritable bowel syndrome (IBS) is common and can be disabling. Several drugs that modulate serotonin (5HT) and other neurotransmitters in the gut (neuroenteric modulators) have either become available or are in development, but progress has been slowed by toxicity. Blockade of 5HT(3) receptors slows colonic transit, increases fluid absorption and increases left colon compliance. Alosetron, a potent 5HT(3) receptor antagonist, has, in women but not in men, a clinically significant but modest therapeutic gain over placebo in the relief of abdominal pain and discomfort and bowel-habit disturbance (but not bloating) in diarrhoea-predominant IBS. However, the drug unexpectedly was associated with ischaemic colitis and, very rarely, severe constipation-induced complications, and alosetron has been withdrawn. Cilansetron may have similar efficacy in men and women. 5HT(4) receptor stimulation results in accelerated colonic transit, and tegaserod, a partial 5HT(4) receptor agonist, has modest but clinically significant advantage over placebo in constipation-predominant IBS; the benefit seems to be confined to females. Long-term published data are lacking and safety concerns have been raised. Prucalopride, a full 5HT(4) agonist that has been promising in idiopathic chronic constipation, may also be limited by toxicity. Other 5HT receptor antagonists and agonists are under development for IBS. However, for modulators of single receptors to achieve a substantial therapeutic gain, and to do so safely, drug targets based on the pathophysiology of IBS need to be better defined.

Irritable bowel syndrome

Irritable bowel syndrome is a common gastrointestinal disorder characterized by abdominal pain and a change in bowel habits. It is estimated to occur in 9% to 22% of the US population, and is more often diagnosed in women than in men. There are no diagnostic markers for irritable bowel syndrome and no evidence of organic disease. Moreover, the pathophysiology is not completely understood; however, abnormal gastrointestinal motility, altered sensory activity, central neural dysfunction, psychological disturbances, and luminal factors have been proposed. Treatment requires a multifaceted approach. Education, dietary measures, fiber supplementation, and pharmacological and psychological interventions have been used in the management of this disorder.

Drug treatment options for irritable bowel syndrome: managing for success

Irritable bowel syndrome (IBS) is a functional gut disorder the diagnosis of which is based on clinical symptoms as set forth by the Rome criteria. As the population ages, especially with the population of patients >75 years of age expanding greatly over the next 10 years, IBS is becoming one of the most common diseases of the elderly. Thus far, developing treatment strategies for patients with IBS has been difficult because of the lack of pharmacological targets and the wide range of symptomatology. Additionally, demonstration of a therapeutic benefit is difficult in the presence of a high placebo response observed regardless of the therapy employed. Fibre, antidiarrhoeals and antispasmodics all play some role in the symptomatic treatment of IBS. With the evolution of IBS as a disorder of visceral hypersensitivity, new drugs have been developed that target the enteric nervous system. Tricyclic antidepressants (TCAs) have been found to target the enteric neurons and play a role in pain modulation. Currently, the TCAs are recommended only for severe cases of IBS pain. The newest class of drugs to be approved for use in IBS are the serotonin (5-hydroxytryptamine; 5-HT) antagonists. Specifically, the 5-HT3 receptor antagonists have been shown to decrease symptoms in female patients with IBS. A related class of drugs, the 5-HT4 receptor agonists, is being developed for the treatment of constipation-predominant IBS. Further investigation into the role of spinal afferent neurons in visceral hypersensitivity is at the forefront of IBS research. Several experimental drug therapies for IBS are also discussed in this review including N-methyl-D-aspartate receptor antagonists, neurokinin-1 receptor antagonists, octreotide, clonidine and the selective M3 receptor antagonist, zamifenacin.

Diarrhea- and Constipation-predominant Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) has a reputation for being hard to treat, trivial, and often psychologic in origin. Furthermore, there currently appears to be almost more of a stigma attached to being diagnosed as having IBS than a depressive illness. Thus, it is not surprising that patients with this syndrome become distressed by the attitudes they encounter, particularly as we now know that this condition can substantially impair one's quality of life. The problem with effective management is that there is no "standard treatment" and therapy has to be targeted to the symptoms of the individual patient. This frequently proves to be time consuming and also may involve some degree of trial and error. However, when all the issues surrounding IBS are addressed in a sympathetic and positive manner, these patients can be surprisingly rewarding to treat.

Postinfectious Irritable Bowel Syndrome

Postinfectious irritable bowel syndrome (PI-IBS) should be considered in patients who present with a change in bowel habits or an onset of new abdominal pain or discomfort following a recent confirmed or presumed exposure to infectious organisms, or in those who have recently returned from a tropical or developing country. In patients who are greatly distressed by their symptoms, an extended workup early in the course of their illness may give physician and patient confidence in focusing on IBS. The author favors a proactive, multicomponent approach to management, as it gives the physician and patient a sense of control. Treatment should include stress management, dietary advice to minimize exposure to trigger foods, and pharmacotherapy to alleviate anxiety and target disturbed physiology.

Irritable bowel syndrome: an update on therapeutic modalities

Irritable bowel syndrome (IBS) is the most common condition that a physician faces in the GI clinic. Of the general population, 10 - 25% suffer from symptoms judged to be IBS. The negative impact of this disease includes not only pain, suffering and direct medical expenses but also significant social and job-related consequences. IBS can be the result of dysfunction in any part of the brain-gut axis: alterations in the CNS caused by psychological or other factors, abnormal gastrointestinal motility, or heightened visceral sensations. Diagnosis is based on either the Manning or Rome-II criteria. Education, reassurance and emotional support are the cornerstones of successful treatment. The mainstays of the current therapeutic approach continue to be: stress management strategies, dietary modification entailing addition of dietary fibre and pharmacotherapy. Pharmacotherapy is still limited to treating symptoms. Newer drugs that modulate motility or drugs that modulate visceral sensation may be useful in selected cases. Psychopharmacological agents are useful in the treatment of IBS, especially in those with psychological co-morbidity. Alternative therapies such as homeopathy, acupuncture, special diets, herbal medication and several forms of psychological treatments and hypnotherapy are sought by many patients and are now being offered by physicians as treatment options, either alone or in conjunction with conventional forms of therapy in patients with refractory symptoms.

Management of the irritable bowel syndrome

Irritable bowel syndrome (IBS) is the most common disorder diagnosed by gastroenterologists and one of the more common ones encountered in general practice. The overall prevalence rate is similar (approximately 10%) in most industrialized countries; the illness has a large economic impact on health care use and indirect costs, chiefly through absenteeism. IBS is a biopsychosocial disorder in which 3 major mechanisms interact: psychosocial factors, altered motility, and/or heightened sensory function of the intestine. Subtle inflammatory changes suggest a role for inflammation, especially after infectious enteritis, but this has not yet resulted in changes in the approach to patient treatment. Treatment of patients is based on positive diagnosis of the symptom complex, limited exclusion of underlying organic disease, and institution of a therapeutic trial. If patient symptoms are intractable, further investigations are needed to exclude specific motility or other disorders. Symptoms fluctuate over time; treatment is often restricted to times when patients experience symptoms. Symptomatic treatment includes supplementing fiber to achieve a total intake of up to 30 g in those with constipation, those taking loperamide or other opioids for diarrhea, and those taking low-dose antidepressants or infrequently using antispasmodics for pain. Older conventional therapies do not address pain in IBS. Behavioral psychotherapy and hypnotherapy are also being evaluated. Novel approaches include alosetron; a 5-HT(3) antagonist, tegaserod, a partial 5-HT(4) agonist, kappa-opioid agonists, and neurokinin antagonists to address the remaining challenging symptoms of pain, constipation, and bloating. Understanding the brain-gut axis is key to the eventual development of effective therapies for IBS.

New therapies for functional bowel diseases

During recent years, a greater understanding of the pathophysiology of functional bowel disease, and a surge of interest in this challenge among pharmacologists, basic scientists, and clinical investigators, have led to novel insights and promising therapies. The evidence to support current therapies in nonculcer dyspepsia and irritable bowel syndrome (IBS) is reviewed, and some of the novel therapeutic approaches on the threshold of clinical application are described.

Therapeutic approach to the patient with irritable bowel syndrome

This article reviews briefly the evidence to support current therapies in irritable bowel syndrome (IBS) and the novel therapeutic approaches on the threshold of clinical application. Fiber is indicated at a dose of at least 12 grams per day in patients with constipation-predominant IBS. Loperamide (and probably other opioid agonists) are of proven benefit in diarrhea-predominant IBS; loperamide may also aid continence by enhancing resting anal tone, but there is no evidence that it results in pain relief. In general, smooth muscle relaxants are best used sparingly, on an as-needed basis, because their overall efficacy is unclear. The 5-HT3 antagonist, alosetron, results in adequate relief of pain and improvements in bowel function in female nonconstipated patients with IBS. Psychotropic agents are important in relieving depression and are of proven benefit for pain and diarrhea in patients with depression associated with IBS. Further trials with selective serotonin reuptake inhibitors are awaited. Psychological treatments including hypnotherapy are less widely available but may play an important role in the relief of pain. In summary, current therapies targeted on the predominant symptoms in IBS are moderately successful. As the bowel sensorimotor and limbic system disturbances of IBS are more clearly understood, we should anticipate other pharmacologic approaches in the near future, including alpha-adrenergic agonists and 5-HT4 agonists. New therapies directed at treatment of the syndrome, rather than relief of symptoms, are needed.

Problems and challenges in the design of irritable bowel syndrome clinical trials: experience from published trials

The last two decades have seen many studies that are of inadequate design and power. This report focuses on what we have learned from the 25 randomized, controlled studies that included at least 30 patients during the period 1976-1998. The most important finding has been that the median placebo response was 47% (range, 0-84%), which is approximately three times the size of the difference between placebo and drug response, median 16% (range, -17-64%). This tells us the importance of reassurance and the powerful nonspecific therapeutic effects of entering patients into clinical trials in irritable bowel syndrome (IBS). Patients should be stratified according to the dominant symptoms that are relevant to the drug's intended effect. A randomized, double-blind, controlled, parallel group study appears the most robust design. Minimizing the placebo response reduces the numbers needed to detect a significant difference. The optimum length of trial is probably >3 months, because the placebo effect takes approximately 12 weeks to start to recede. Dose titration should maximize the chance of detecting a benefit.

Review article: clinical evidence to support current therapies of irritable bowel syndrome

This review summarizes the clinical evidence to support current therapies in irritable bowel syndrome (IBS). Fibre is indicated at a dose of at least 12 g per day in patients with constipation-predominant IBS. Loperamide (and probably other opioid agonists) are of proven benefit in diarrhoea-predominant IBS; loperamide may also aid continence by enhancing resting anal tone. In general, smooth muscle relaxants are best used sparingly, on an 'as needed' basis, as their overall efficacy is unclear. Psychotropic agents are important in relieving depression and of proven benefit for pain and diarrhoea in patients with depression associated with IBS. Further trials with selective serotonin reuptake inhibitors (SSRIs) are awaited. Psychological treatments including hypnotherapy are less widely available, but may play an important role in relief of pain. In summary, current therapies targeted on the predominant symptoms in IBS are moderately successful. New therapies are needed to more effectively relieve this syndrome, not just symptoms.

Irritable Bowel Syndrome

I believe there are four essential elements in the management of patients with irritable bowel syndrome (IBS): to establish a good physician-patient relationship; to educate patients about their condition; to emphasize the excellent prognosis and benign nature of the illness; and to employ therapeutic interventions centering on dietary modifications, pharmacotherapy, and behavioral strategies tailored to the individual. Initially, I establish the diagnosis, exclude organic causes, educate patients about the disease, establish realistic expectations and consistent limits, and involve patients in disease management. I find it critical to determine why the patient is seeking assistance (eg, cancer phobia, disability, interpersonal distress, or exacerbation of symptoms). Most patients can be treated by their primary care physician. However, specialty consultations may be needed to reinforce management strategies, perform additional diagnostic tests, or institute specialized treatment. Psychological co-morbidities do not cause symptoms but do affect how patients respond to them and influence health care-seeking behavior. I find that these issues are best explored over a series of visits when the physician-patient relationship has been established. It can be helpful to have patients fill out a self-administered test to identify psychological co-morbidities. I often use these tests as a basis for extended inquiries into this area, resulting in the initiation of appropriate therapies. I encourage patients to keep a 2-week diary of food intake and gastrointestinal symptoms. In this way, patients become actively involved in management of their disease, and I may be able to obtain information from the diary that will be valuable in making treatment decisions. I do not believe that diagnostic studies for food intolerances are cost-effective or particularly helpful; however, exclusion diets may be beneficial. I introduce fiber supplements gradually and monitor them for tolerance and palatability. Synthetic fiber is often better-tolerated than natural fiber, but must be individualized. In my experience, excessive fiber supplementation often is counterproductive, as abdominal cramps and bloating may worsen. Antidiarrheal agents are very effective when used correctly, preferably in divided doses. I use them in patients in anticipation of diarrhea and especially in those who fear symptoms when engaged in activities outside the home. I encourage patients to make decisions as to when and how much to use. However, almost always, a morning dose before breakfast is used (loperamide, 2 to 6 mg) and, perhaps again later in the day when symptoms of diarrhea are prominent. I prefer antispasmodics to be used intermittently in response to periods of increased abdominal pain, cramps, and urgency. For patients with daily symptoms, especially after meals, agents such as dicyclomine before meals are useful. For patients with infrequent but severe episodes of unpredictable pain, sublingual hyoscyamine often produces rapid relief and instills confidence. In general, I recommend that oral antispasmodics be used for a limited period of time rather than indefinitely, and generally for periods of time when symptoms are prominent. For chronic visceral pain syndromes, I recommend small doses of tricyclic antidepressants. These agents are especially effective in diarrhea-predominant patients with disturbed sleep patterns but may be unacceptable to patients with constipation. I educate patients that side effects occur early and benefits may not be apparent for 3 to 4 weeks. I consider using SSRIs in low doses in patients with constipation-predominant IBS; cisapride, 10 to 20 mg three times per day, also may be beneficial. When taken with drugs that inhibit cytochrome P450, cisapride has been associated with serious cardiac arrhythmias caused by QT prolongation, including ventricular arrhythmias and torsades de pointes. These drugs include the azole fungicides; erythromycin, clarithromycin, and troleandomycin; some antidepressants; HIV protease inhibitors; and others. In patients with IBS with mild to moderate co-morbid depression, I have found that the use of SSRIs such as paroxetine, fluoxetine, or sertraline may be beneficial. It is important to tell patients that anxiety and disturbed sleep may occur during the first 10 days and benefits may not occur for 3 to 4 weeks. I prescribe a small amount of a short-acting benzodiazepine such as alprazolam, 0.5 mg two times per day, to control these symptoms. For generalized anxiety without depression, buspirone or clonazepam may be useful. I have found that patients who also have associated panic disorder may benefit from a benzodiazepine, tricyclic antidepressant, or an SSRI. However, these patients are best managed in conjunction with a psychiatrist or psychologist. I consider the use of alternative therapies in patients who fail to respond to conventional measures and who are receptive to alternative strategies. These include general relaxation techniques such as biofeedback and hypnosis therapies.

Biofeedback training in patients with fecal incontinence

PURPOSE

This study was undertaken to assess the functional results of biofeedback training in patients with fecal incontinence in relation to clinical presentation and anorectal manometry results.

METHODS

Twenty-six consecutive patients with fecal incontinence were treated with biofeedback training using anorectal manometry pressure for visual feedback. Ten patients had passive incontinence only, six patients had urge incontinence, and ten patients had combined passive and urge incontinence.

RESULTS

Patients with urge incontinence had a lower maximum voluntary contraction pressure (92+/-12 mmHg) and a lower maximum tolerable volume (78+/-13 ml) than patients with passive incontinence (140+/-43 mmHg and 166+/-73 ml). Twenty-two patients completed the treatment, five patients (23 percent) showed excellent improvement, nine patients (41 percent) had good results, and eight (36 percent) patients showed no improvement. At follow-up on average of 21 months after therapy, 41 percent of our patients reported continued improvement. The maximum tolerable volume was higher in those with excellent (140.4+/-6.8 ml) or good (156.3+/-6.64 ml) results of therapy than it was in those with poor results (88.5+/-2.5 ml). Greater asymmetry of the anal sphincter also correlated to poor results.

CONCLUSION

Biofeedback therapy improved continence immediately after training and at follow-up after 21 months, but the initial results were better. The urge fecal incontinence seems to be related to function of the external anal sphincter and to the maximum tolerable volume. Low maximum tolerable volume and anal sphincter asymmetry were associated with a poor outcome of therapy.

A biopsychosocial understanding of the irritable bowel syndrome: a review

OBJECTIVES

To review and examine the clinical and research literature on irritable bowel syndrome (IBS) with a view to establishing the role that psychiatric factors play in the pathogenesis and treatment of this syndrome.

RESULTS

Comorbid psychiatric illness is common with IBS, yet only a small proportion of these patients seek medical attention. Many patients are either satisfied by reassurance or experience symptom relief from medical treatment directed at target symptoms. A small group of patients do not experience much relief, and it is largely this group who come to the psychiatrist's attention. Psychotropic medication is helpful when clinically indicated, and tricyclic antidepressants in small doses (for example, 50 mg) may be helpful for those patients with a pain-predominant pattern of IBS. Psychotherapy (including cognitive, behavioural, relaxation, thermal-biofeedback, insight-oriented therapy, and hypnosis) has been shown to provide relief, although it has often been difficult to differentiate this improvement from a placebo response.

CONCLUSIONS

The group of patients with "refractory IBS" used a large amount of health care resources in an attempt to find relief to their distress. Further study is needed to gain a better understanding of which component of psychotherapy is most cost-effective and which patients are most likely to benefit. The large group of those who admit to symptoms compatible with IBS but who do not seek medical attention has to a large extent been excluded from most studies. Exploring this group may provide further insight into this perplexing syndrome.

Review article: irritable bowel syndrome

Irritable bowel syndrome is a disease that can be diagnosed positively on the basis of an established series of criteria and limited exclusion of organic disease. It is the most common disease diagnosed by gastroenterologists and affects about 20% of all people at any one time. Symptoms fluctuate, and the overall prevalence rate is relatively constant in Western communities. Ten per cent of patients present to their physicians; the illness has a large economic impact on health-care utilization and absenteeism. Irritable bowel syndrome is a biopsychosocial disorder in which three major mechanisms interact: psychosocial factors; altered motility; and/or sensory function of the intestine. Management of patients is based on positive diagnosis of the symptom complex, limited exclusion of underlying organic disease and institution of a therapeutic trial. If patient symptoms are intractable, further investigations are needed to exclude significant motility or other disorders. Symptomatic treatment includes fibre for constipation, loperamide for diarrhoea and low-dose antidepressants or infrequent use of antispasmodics for pain; novel pharmacological agents, psychotherapy and hypnotherapy are being evaluated.

Effects of loperamide oxide on gastrointestinal transit time and anorectal function in patients with chronic diarrhoea and faecal incontinence

BACKGROUND

Loperamide improves anorectal function in patients with chronic diarrhoea. We wished to investigate whether the prodrug loperamide oxide has similar effects.

METHODS

Eleven patients with chronic diarrhoea and faecal incontinence participated in a randomized, placebo-controlled, double-blind, crossover study of the effects of loperamide oxide (4 mg twice daily for 1 week).

RESULTS

Loperamide oxide reduced wet stool weight and improved the patients' ratings of symptoms. Mouth-to-caecum transit time was not altered, but whole-gut transit time was prolonged. There were limited effects on anorectal function, but the mean minimum basal pressure mainly contributed by the internal anal sphincter (IAS) was increased, as was the mean volume infused before leakage occurred in the saline continence test.

CONCLUSION

Loperamide oxide is effective in the treatment of diarrhoea with faecal incontinence; normalization of colon transit time and an increase in the tone of the IAS seem to be the main determinants of efficacy.

Newer aspects of the irritable bowel syndrome

IBS is a challenging, functional GI disorder that affects many individuals around the world. Early life experiences, the biologic nature of the condition, and the psychosocial milieu interact to affect the severity and outcome of symptoms. Most people do not seek medical attention for their GI symptoms, or they require intermittent, limited medical therapy and assurance from their physician. Fewer patients, but still a significant number, demand frequent interaction with their physician, who may select pharmacotherapy or psychological and behavioral treatments to control symptoms, depending on the severity. A biopsychosocial approach with attention to the patient-doctor relationship is recommended as the basis for treatment.

High dose loperamide suppositories: a novel approach for improving clinical function after restorative proctocolectomy

The effect of loperamide suppositories on patients following restorative proctocolectomy was studied by means of a randomized, double-blind, crossover trial comparing active suppositories (20 mg b.d. x 1 week) with placebo. Ten patients (8 male, 2 female; 7 J pouch, 3 W pouch; 8 ulcerative colitis, 2 familial adenomatous polyposis) were studied 3-60 months (median, 31.5) after ileostomy closure. Ages ranged from 24 to 63 years (medium, 41.5). All patients kept a diary of their bowel habits and eight underwent a standardized test of pouch compliance. Urgency volume (UV) and maximum tolerable volumes (MTV) and the volume at onset of large isolated pouch contractions (LIC) were recorded. Statistical analysis was by the Wilcoxon test for paired data. Mean daily stool frequency during the placebo phase ranged from 3.7 to 7.8. It was reduced during the active phase in only seven patients (P > 0.1) but was reduced in all six patients whose placebo phase stool frequency was five or more. Urgency volume was increased by use of active suppositories in six of the eight patients tested (P > 0.01). There was no consistent effect on MTV. Large isolated pouch contractions were not seen in either test in one patient. In all of the remaining seven patients LIC were recorded after the placebo phase. After the active phase LIC first appeared at higher volumes in three but were not seen at all in four patients. High dose loperamide suppositories suppress pouch contractions and tend to lower stool frequency especially when high initially. They represent a novel therapeutic approach to high stool frequency in pouch patients.

A double-blind, placebo-controlled study of a CCK-B receptor antagonist, CI-988, in patients with generalized anxiety disorder

This multicenter, double-blind, placebo-controlled, parallel-group, randomized study assessed the efficacy, safety, and tolerability of a novel CCK-B antagonist CI-988 in the treatment of generalized anxiety disorder (GAD). Patients received placebo or CI-988 (300 mg/day, thrice daily) for 4 weeks. Patients with a primary diagnosis of GAD according to DSM-III-R criteria were randomized. The study design included a 1- to 2-week single-blind placebo baseline phase, followed by a 4-week double-blind treatment phase. Efficacy was measured weekly by Hamilton Rating Scale for Anxiety (HAM-A), Clinical Global Impressions of Severity and Change, UCLA-Multi Dimensional Anxiety Scale, and Hamilton Rating Scale for Depression. Patients were also evaluated to determine whether they met criteria for irritable bowel syndrome (IBS) at screening and were evaluated with a gastrointestinal visual analog scale at each visit. Eighty-eight patients were randomized to CI-988 (N = 45) and placebo (N = 43) at three centers. CI-988 did not demonstrate an anxiolytic effect superior to placebo in this clinical trial. There was no significant difference in mean change in HAM-A total between placebo (-7.73) and CI-988 (-8.64). However, a significant treatment-by-center interaction and a highly variable placebo response rate among the three centers limit the interpretation of the results. CI-988 did not have an effect on symptoms of IBS other than diarrhea, which worsened in patients with IBS. Other than a higher incidence of some gastrointestinal symptoms (diarrhea, dyspepsia, flatulence, and nausea), CI-988 was well tolerated. Results suggest that testing higher oral doses of CI-988 may be warranted.

Loperamide. Survey of studies on mechanism of its antidiarrheal activity

In castor oil challenged rats, low doses of loperamide inhibit diarrhea and normalize intestinal propulsion. Unlike other opioids, loperamide is devoid of central opiate-like effects, including blockade of intestinal propulsion, up to the highest subtoxic oral dose. Nevertheless, the antidiarrheal action of loperamide can be considered to be mu-opiate receptor mediated, only a few in vitro effects at rather high concentrations being not naloxone-reversible. There is little evidence that interactions with intestinal opiate receptors directly change epithelial cell function. When secretory stimuli increase mucosal tension, however, loperamide may reverse the elevated hydrostatic tissue pressure that opposes normal absorption. This antisecretory effect at the mucosal level is accompanied by motor effects when loperamide reaches the myenteric mu-opiate receptors. At therapeutic doses for the treatment of acute diarrhea, it is likely that the mucosal effect prevails.

Effect of loperamide and delay of bowel motility on bile acid malabsorption caused by late radiation damage and ileal resection

Selenium-75 homocholic acid conjugated with taurine (75Se-HCAT) was used during loperamide administration in seven patients suspected of having bile acid malabsorption due to late radiation damage and small-bowel resection in order to document the aetiology of ileal dysfunction and to adjust therapeutic management. In two patients with ileal resection up to 50 cm and in one patient without resection, a reduction of bowel motility by loperamide resulted in marked normalization of the 75Se-HCAT retention measurements. Sequential scintigraphic 75Se-HCAT imaging demonstrated a significant improvement in the 75Se-HCAT reabsorption and recirculation, accompanied in one case by prolongation of colonic retention of the radiopharmaceutical. In four patients with more than 80 cm resection, the 75Se-HCAT test was abnormal during loperamide administration. In two of these patients for whom baseline values were available, no improvement in the pattern of 75Se-HCAT absorption was observed. In conclusion, the first results of loperamide 75Se-HCAT in patients suspected of having bile acid malabsorption and abnormal baseline 75Se-HCAT are promising. Intervention with loperamide is easy and seems to improve the clinical value of the test with direct therapeutic implications. Sequential 75Se-HCAT imaging is essential for interpreting changes in the 75Se-HCAT retention measurements.

The effect of loperamide on bowel habits and anal sphincter function in patients with ileoanal anastomosis

The effect of loperamide on stool frequency, volume, and weight and on the function of the internal (IAS) and the external (EAS) anal sphincter was investigated in 19 patients with straight ileoanal anastomosis. Nine patients had intact anal sphincter function (group I), and in the other 10 the function of the anal sphincters was impaired (group II). After 72 h without any medication, the patients were investigated on a standard diet on 2 consecutive days: the 1st day with placebo, and the 2nd day with loperamide (16 mg). Stool collection and anal sphincter manometry/electromyography (EMG) were done on both days. The median number of stools was reduced from 10 and 13.5 to 6 and 7 per 24 h (p less than 0.01), and the fecal weight reduced from 600 and 900 g to 400 and 500 g (p less than 0.01) from the placebo day to the loperamide day in groups I and II, respectively. The tone of the IAS was significantly increased by loperamide in group I but remained unchanged in group II patients. The EAS function, determined by EMG and pressure measurements, was not significantly changed in any group by loperamide.

A double-blind crossover comparison of lidamidine, loperamide and placebo for the control of chronic diarrhoea

Fourteen patients with chronic diarrhoea, but no evidence of active organic disease, completed a double-blind crossover comparison of the anti-diarrhoeal effects of loperamide, placebo and the clonidine analogue, lidamidine. Failure of diarrhoea control led to early withdrawals from seven placebo- and six lidamidine-treatment periods, but there was only one early withdrawal during treatment with loperamide. Loperamide was found to be superior to lidamidine or placebo for the control of stool consistency in patients with chronic diarrhoea.

Controlled treatment trials in the irritable bowel syndrome: a critique

The irritable bowel syndrome (IBS) is a common and poorly understood chronic condition that is treated with a great variety of drugs and other therapies without notable enduring success. As there are no objective markers of improvement, and because there may be a very large placebo response, potential treatments for IBS are difficult to assess. Probably the only method that can reliably evaluate IBS therapies is the randomized, double-blind, placebo-controlled treatment trial. The purpose of this review is to critically examine issues central to establishing the efficacy of treatments for IBS in such trials. These include the definition of IBS, measures of efficacy, the placebo response, trial length, maintaining blindedness, the crossover design, ability to generalize, and statistical considerations. With this background, all published IBS treatment trials are examined. It is concluded that not a single study offers convincing evidence that any therapy is effective in treating the IBS symptom complex. Well-designed and executed IBS treatment trials are urgently needed; suggestions are given for essential features of such trials.