Tegaserod

Tegaserod maleate exerts anti-tumor effects on prostate cancer via repressing sonic hedgehog signaling pathway

Prostate cancer (PCa) is a highly common type of malignancy and affects millions of men in the world since it is easy to recur or emerge therapy resistance. Therefore, it is urgent to find novel treatments for PCa patients. In the current study, we found that tegaserod maleate (TM), an FDA-approved agent, inhibited proliferation, colony formation, migration as well as invasion, caused the arrest of the cell cycle, and promoted apoptosis of PCa cells in vitro. In addition, TM suppressed the tumor growth in the cell-derived xenograft (CDX) mouse model in vivo. Mechanistically, TM exerted anti-tumor effects via downregulating GLI2, and its downtream targets, thus inhibiting the sonic hedgehog (SHH) signaling pathway. In brief, our findings demonstrated that TM effectively inhibited the activities of PCa cells by suppressing the SHH signaling pathway and provided a potential new agent for the treatment of PCa.

Tegaserod for the Treatment of Irritable Bowel Syndrome

Background: Tegaserod (Zelnorm®) is a 5-hydroxytryptamine (serotonin) type 4 receptor agonist for the treatment of hypomotility disorders of the lower gastrointestinal tract associated with the irritable bowel syndrome with constipation (IBS-C).

Objective: The authors provide the reader with a better understanding on tegaserod mechanism of action, on its pharmacodynamics and pharmacokinetic properties, on safety and tolerability, with a summary of the key published clinical trials conducted in patients with irritable bowel syndrome (IBS). Its effects on colon inflammation have also been described.

Results: Tegaserod was withdrawn in 2007 due to increased risks of cardiovascular adverse effects. The manufacturer denied this, because pre-existing cardiovascular disease or risk factors were attributed to all affected patients. Thus, no causal relationship between tegaserod use and cardiovascular events was clearly shown. A matched case-control study of tegaserod-treated with untreated patients found no association between tegaserod and adverse cardiovascular outcomes. Despite its adverse effects, tegaserod resulted to be effective in treating chronic constipation in adult women aged < 65 years with IBS-C, while the safety and effectiveness of tegaserod in men with IBS-C have not been established.

Conclusion: Tegaserod was resubmitted to the Food and Drug Administration in 2018 for use in a low-risk population. Moreover, tegaserod has also been shown to improve symptoms, enhance gastric accommodation and significantly attenuate visceral pain arising from the colon in functional dyspepsia patients. Treatment with tegaserod seems also to exert a protective effect in inflamed colons, reducing the severity of colitis in animal models.

Targeted pharmacotherapy of irritable bowel syndrome

PURPOSE OF REVIEW

Irritable bowel syndrome (IBS) is a highly prevalent functional gastrointestinal (GI) disorder with negative impact on quality of life and it represents a substantial economic burden on healthcare cost. The medical management of IBS is symptom directed. This review provides an update related to clinical trial data for novel treatment modalities in IBS targeting the gut epithelium secretagogue receptors and channels.

RECENT FINDINGS

The new Rome IV criteria define functional gastrointestinal disorders (FGID) as disorders of the gut-brain interaction. Pharmacological treatment modalities for IBS target gastrointestinal receptors and ion channels, peripheral opioid receptor, gut serotonin receptors, and the gut microbiome. New targeted pharmacotherapies have shown efficacy and safety in the treatment of patients with IBS.

SUMMARY

Diagnostic criteria for FGID, including IBS, have been revised in Rome IV and are defined as gut-brain disorders. Newly approved pharmacotherapy options with proven efficacy and acceptable side-effect profiles are available for the symptom-based management of IBS.

Sex-Gender Differences in Irritable Bowel Syndrome

Because of the sex-gender differences that are shown in a diversity of physiological and psychological factors, it can be speculated that the clinical presentation of symptoms as well as treatment strategies in women and men with irritable bowel syndrome (IBS) may differ. Studies have revealed that IBS is more common in women than men. As for the IBS subtype, IBS with constipation is significantly more prevalent among women than men. Sex hormones and gender differences may play important roles in the pathophysiology of IBS. However, its pathophysiologic mechanisms still remain largely unknown, and therapeutic implications are limited. Moreover, women IBS patients have been reported to feel more fatigue, depression, anxiety, and lower quality of life than men IBS patients. Furthermore, there has been evidence of differences in the appropriate treatment efficacy to IBS in men and women, although relatively few men are enrolled in most relevant clinical trials. A more sex-gender-oriented approach in the medical care setting could improve understanding of heterogeneous patients suffering from IBS. An individualized and multicomponent approach including sex and gender issues might help improve the treatment of IBS.

Irritable Bowel Syndrome: Epidemiology, Pathophysiology, Diagnosis, and Treatment

Irritable bowel syndrome is a common medical condition that significantly alters patient quality of life and presents a series of diagnostic and treatment challenges to the treating provider. This article provides an updated and straightforward overview of the disease, its pathophysiology, diagnosis, and treatment options.

New treatment targets for the management of irritable bowel syndrome

PURPOSE OF REVIEW

Irritable bowel syndrome (IBS) and chronic idiopathic constipation (CIC) are highly prevalent medical conditions that reduce quality of life and represent a substantial economic burden on healthcare cost. Until recently, no specific treatment options were available. This review will provide an update of the most recent randomized clinical trials data showing efficacy and safety of novel, targeted treatment modalities in IBS and CIC with gastrointestinal receptor and ion channel agonists.

RECENT FINDINGS

Recent discoveries of peptides and small molecules targeting gastrointestinal receptors and ion channels resulted in novel, specific pharmacological therapies of IBS and CIC. The bicyclical fatty acid lubiprostone and the synthetic 14-amino acid peptide linaclotide were identified to selectively activate a Chloride Channel-2 and the Guanylin Cyclase-C receptor, respectively, and demonstrate efficacy in the treatment of IBS with constipation and CIC.

SUMMARY

Novel molecules including the bicyclical fatty acid lubiprostone and the synthetic 14-amino acid peptide linaclotide represent new treatment modalities for IBS with constipation and CIC with proven efficacy and acceptable side-effect profiles.

Irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder that leads to crampy pain, gassiness, bloating, and changes in bowel habits in the absence of any currently identifiable organic disorder. Patients with IBS may be classified by their predominant bowel habit: diarrhea-predominant, constipation-predominant, or IBS with alternating bowel movements. IBS is often associated with stress or anxiety. Although IBS can be frustrating and concerning to patients with this disorder, it does not cause permanent harm to the intestines and does not lead to a serious disease such as cancer. Although treatments exist for its symptoms, there is no known cure.

Future role of gastroenterologists in digestive oncology in the Asia Pacific region: Panir Chelvam Memorial Lecture, Asian Pacific Digestive Week 2010

There is an increasing burden in digestive cancer in the coming years. With the advancement of endoscopic therapy, new molecular target therapy and minimally invasive ablation therapy, the treatment of digestive cancer will become more complicated. In Asia where gastric cancer and hepatocellular carcinoma are still prevalent and colorectal cancer is rapidly on the rise, the need in digestive oncology will be even higher. A new subspecialty of digestive oncology will be needed from the patient's perspective, from the healthcare authority's viewpoint and for the future development of gastroenterology.

Pharmacology and metabolism of renzapride : a novel therapeutic agent for the potential treatment of irritable bowel syndrome

BACKGROUND AND OBJECTIVE

Renzapride (ATL-1251), a novel benzamide, is currently under clinical development for the treatment of irritable bowel syndrome (IBS). Previous in vitro and in vivo experimental studies have characterized renzapride as a full serotonin 5-HT(4) receptor agonist on the gut and a 5-HT(3) receptor antagonist. Clinical studies have confirmed the therapeutic efficacy, tolerability and safety of renzapride in patients with constipation-predominant IBS. This study set out to characterize the pharmacological profile of renzapride and its potential metabolic products at both 5-HT and other monoamine receptors in the gut.

METHODS

The affinity of renzapride, its (+) and (-) enantiomers, and its primary metabolite, renzapride N-oxide and its enantiomers, for serotonin receptors was assessed by means of in vitro radioligand binding inhibition studies. After membranes prepared from animal tissue or membranes of cell lines transfected with cloned human receptors had been incubated with radiolabelled ligand with high affinity for a specific receptor, renzapride was added to competitively inhibit this binding. Levels of bound radioligand were measured by filtration and counting of the bound radioactivity. In instances where >50% inhibition of radioligand binding had occurred, the inhibition constant (K(i)) was calculated. Metabolism of renzapride by liver microsomes was assessed by incubating 10 micromol/L renzapride with human liver microsome samples for 60 minutes at 37 degrees C. After the reaction was stopped, the samples were centrifuged and the supernatant analysed for metabolites by high-pressure liquid chromatography (HPLC). The potential inhibitory effects of renzapride on cytochrome P450 (CYP) enzymes were assessed by incubating renzapride at various concentrations over a 1-500 micromol/L concentration range with microsomes genetically engineered to express a single CYP.

RESULTS

Renzapride was selective for serotonergic receptors and, in particular, had high affinity for human 5-HT(3) and guinea-pig 5-HT(4) receptors (K(i) 17 and 477 nm, respectively). Inhibitory properties at 5-HT(2B) receptors were also identified for renzapride, as well as some affinity for 5-HT(2A) and 5-HT(2C) receptors. Renzapride N-oxide and its enantiomers demonstrated much lower affinity for all 5-HT receptors compared with renzapride. Renzapride was metabolized by liver microsomes to a limited extent and there was no significant non-microsomal metabolism of renzapride. Renzapride did not inhibit the major CYP drug-metabolizing enzymes CYP2C9, CYP2D6, CYP1A2, CYP2A6, CYP2C19, CYP2E1 or CYP3A4 at concentrations consistent with use in a clinical setting.

CONCLUSIONS

These results confirm and extend earlier studies in animal and human receptors that show renzapride is a potent and generally full 5-HT(4) receptor agonist and 5-HT(3) receptor antagonist. The results reported in the present study indicate that the metabolites of renzapride are minor and are unlikely to contribute to its therapeutic profile or lead to interaction of renzapride with other drugs that inhibit the major drug-metabolizing enzymes in the liver at therapeutic doses. These data contribute to the understanding of the pharmacological actions and metabolic fate of renzapride in vivo.

Serotonin and neuroprotection in functional bowel disorders

The 5-HT(4) partial agonist tegaserod is effective in the treatment of chronic constipation and constipation predominant irritable bowel syndrome. 5-HT(4) receptors are located on presynaptic terminals in the enteric nervous system. Stimulation of 5-HT(4) receptors enhances the release of acetylcholine and calcitonin gene related peptide from stimulated nerve terminals. This action strengthens neurotransmission in prokinetic pathways, enhancing gastrointestinal motility. The knockout of 5-HT(4) receptors in mice not only slows gastrointestinal activity but also, after 1 month of age, increases the age-related loss of enteric neurons and decreases the size of neurons that survive. 5-HT(4) receptor agonists, tegaserod and RS67506, increase numbers of enteric neurons developing from precursor cells and/or surviving in culture; they also increase neurite outgrowth and decrease apoptosis. The 5-HT(4) receptor antagonist, GR113808, blocks all of these effects, which are thus specific and 5-HT(4)-mediated. 5-HT(4) receptor agonists, therefore, are neuroprotective and neurotrophic for enteric neurons. Because the age-related decline in numbers of enteric neurons may contribute to the dysmotilities of the elderly, the possibility that the neuroprotective actions of 5-HT agonists can be utilized to prevent the occurrence or worsening of these conditions should be investigated.

Serotonin and neuroprotection in functional bowel disorders

The 5-HT(4) partial agonist tegaserod is effective in the treatment of chronic constipation and constipation predominant irritable bowel syndrome. 5-HT(4) receptors are located on presynaptic terminals in the enteric nervous system. Stimulation of 5-HT(4) receptors enhances the release of acetylcholine and calcitonin gene related peptide from stimulated nerve terminals. This action strengthens neurotransmission in prokinetic pathways, enhancing gastrointestinal motility. The knockout of 5-HT(4) receptors in mice not only slows gastrointestinal activity but also, after 1 month of age, increases the age-related loss of enteric neurons and decreases the size of neurons that survive. 5-HT(4) receptor agonists, tegaserod and RS67506, increase numbers of enteric neurons developing from precursor cells and/or surviving in culture; they also increase neurite outgrowth and decrease apoptosis. The 5-HT(4) receptor antagonist, GR113808, blocks all of these effects, which are thus specific and 5-HT(4)-mediated. 5-HT(4) receptor agonists, therefore, are neuroprotective and neurotrophic for enteric neurons. Because the age-related decline in numbers of enteric neurons may contribute to the dysmotilities of the elderly, the possibility that the neuroprotective actions of 5-HT agonists can be utilized to prevent the occurrence or worsening of these conditions should be investigated.

Differences between the abilities of tegaserod and motilin receptor agonists to stimulate gastric motility in vitro

BACKGROUND AND PURPOSE

Motilin or 5-HT4 receptor agonists stimulate gastrointestinal motility. Differences in activity are suggested but direct comparisons are few. A method was devised to directly compare the gastric prokinetic activities of motilin, the motilin receptor agonist, erythromycin, and the 5-HT4 receptor agonist, tegaserod.

EXPERIMENTAL APPROACH

Gastric prokinetic-like activity was assessed by measuring the ability to facilitate cholinergically-mediated contractions evoked by electrical field stimulation (EFS) in rabbit isolated stomach. Comparisons were made between potency, maximal activity and duration of responses.

KEY RESULTS

Rabbit motilin (r.motilin) 0.003-0.3 microM, [Nle13]motilin 0.003-0.3 microM, erythromycin 0.3-10 microM and tegaserod 0.1-10 microM caused concentration - dependent potentiation of EFS-evoked contractions. The potency ranking was r.motilin = [Nle13]motilin > tegaserod > erythromycin. The Emax ranking was r.motilin = [Nle13]motilin = erythromycin > tegaserod. Responses to r.motilin and [Nle13]motilin faded rapidly (t1/2 9 and 11 min, respectively) whereas those to erythromycin and tegaserod were maintained longer (t1/2 24 and 28 min). The difference did not appear to be due to peptide degradation. A second application of [Nle13]motilin was excitatory after 60 min contact and fade of the initial response (responses to 0.03 and 0.1 microM [Nle13]motilin were not different from those caused by the first application).

CONCLUSIONS AND IMPLICATIONS

Prokinetic-like activities of the 5-HT4 agonist tegaserod and the motilin receptor agonists were compared by measuring changes in cholinergically-mediated contractions. This novel approach highlighted important differences between classes (greater Emax of motilin, compared with tegaserod) and for the first time, within each class (short t1/2 for motilin, compared with erythromycin).

Serotonergic and non-serotonergic targets in the pharmacotherapy of visceral hypersensitivity

Visceral hypersensitivity is considered a key mechanism in the pathogenesis of functional gastrointestinal (GI) disorders. Targeting visceral hypersensitivity seems an attractive approach to the development of drugs for functional GI disorders. This review summarizes current knowledge on targets for the treatment of visceral hypersensitivity, and the status of current and future drug and probiotic treatment development, and the role of pharmacogenomic factors.

Pilot study of the efficacy of renzapride on gastrointestinal motility and symptoms in patients with constipation-predominant irritable bowel syndrome

AIM

To investigate the efficacy and safety of renzapride, a potent 5-hydroxytryptamine type-4 receptor full agonist and 5-hydroxytryptamine type-3 receptor antagonist in patients with constipation-predominant irritable bowel syndrome.

METHODS

In this dose-escalating pilot study, 17 patients with constipation-predominant irritable bowel syndrome received placebo, renzapride 2 mg o.d. and renzapride 2 mg b.d. sequentially for 28 days. Response was determined by radio-opaque marker measurement of overall gastrointestinal and segmental colonic transit and patients' assessment of their irritable bowel syndrome symptoms.

RESULTS

Renzapride reduced mean overall gastrointestinal transit time (placebo, 2.9 +/- 1.6 days; renzapride 2 mg o.d., 2.6 +/- 1.4 days; renzapride 2 mg b.d., 1.9 +/- 1.6 days) (P = 0.024) and accelerated segmental colonic transit, with statistically significant differences for renzapride 2 mg b.d. over placebo in caecum/ascending colon (P = 0.019) and descending colon (P = 0.022). Renzapride also reduced abdominal pain, increased the number of pain-free days and improved stool consistency. The frequency of reported adverse events was similar on renzapride and placebo.

CONCLUSIONS

Renzapride is well-tolerated, stimulates gastrointestinal transit and improves symptoms in patients with constipation-predominant irritable bowel syndrome, particularly at the 2 mg b.d. dose, where improvements in gastrointestinal symptoms were evident over placebo. This study has established proof of concept and supports further investigation of renzapride in patients with constipation-predominant irritable bowel syndrome.

The spectrum of irritable bowel syndrome: A clinical review

BACKGROUND

Irritable bowel syndrome (IBS) is associated with a substantial burden on individual patients, health care systems, and society as a whole.

OBJECTIVES

This review article provides an overview of the disease state and discusses treatment options.

METHODS

The MEDLINE database was searched for original research and review articles published in English (from 1966 to July 2005) using the medical subject heading irritable bowel syndrome and the following subheadings: diagnosis, economics, pathophysiology, and therapy. Preference was given to articles that focused on new insights regarding pathophysiology and to those that addressed global symptom improvement for IBS.

RESULTS

Symptoms of IBS vary with each patient and disease episode. Although improvement in individual IBS symptoms is desirable, the overall goal in managing patients with IBS is to achieve global symptom improvement. Traditional IBS therapies (ie, psychotherapy/behavioral therapy, bulking agents, antidiarrheals, antispasmodics, and tricyclic antidepressants) have lacked demonstrable efficacy in randomized controlled trials. Recent improvements in the understanding of IBS pathophysiology, particularly regarding the role of neurotransmitters and hormones in gastrointestinal motility, secretion, and visceral perception, have resulted in the development of novel treatments for IBS. In clinical trials, IBS-specific treatments (ie, agents that affect serotonergic pathways) have been associated with significant improvements in global symptoms. However, the added cost of treatment with these agents and the potential risks of serious adverse events (eg, severe constipation, severe diarrhea, ischemic colitis) may preclude their widespread use. Initial cost-effectiveness analyses with the novel IBS-specific agents suggest the benefits may outweigh the added costs. From a managed care perspective, the costs incurred by IBS-specific therapies may be offset by subsequent reductions in health care resource utilization by patients with IBS.

CONCLUSIONS

IBS-specific agents offer an opportunity for patients with IBS to achieve global symptom improvement. However, when weighing the costs and potential risks against the potential benefits, clinicians should consider the nature and severity of the patient's symptoms, the degree of functional impairment, and the presence of psychosocial comorbidities.

Review article: serotonin receptors and transporters -- roles in normal and abnormal gastrointestinal motility

The gut is the only organ that can display reflexes and integrative neuronal activity even when isolated from the central nervous system. This activity can be triggered by luminal stimuli that are detected by nerves via epithelial intermediation. Epithelial enterochromaffin cells act as sensory transducers that activate the mucosal processes of both intrinsic and extrinsic primary afferent neurones through their release of 5-hydroxytryptamine (5-HT). Intrinsic primary afferent neurones are present in both the submucosal and myenteric plexuses. Peristaltic and secretory reflexes are initiated by submucosal intrinsic primary afferent neurones, which are stimulated by 5-HT acting at 5-HT(1P) receptors. 5-HT acting at 5-HT4 receptors enhances the release of transmitters from their terminals and from other terminals in prokinetic reflex pathways. Signalling to the central nervous system is predominantly 5-HT3 mediated, although serotonergic transmission within the enteric nervous system and the activation of myenteric intrinsic primary afferent neurones are also 5-HT3 mediated. The differential distribution of 5-HT receptor subtypes makes it possible to use 5-HT3 antagonists and 5-HT4 agonists to treat intestinal discomfort and motility. 5-HT3 antagonists alleviate the nausea and vomiting associated with cancer chemotherapy and the discomfort from the bowel in irritable bowel syndrome; however, because 5-HT-mediated fast neurotransmission within the enteric nervous system and the stimulation of mucosal processes of myenteric intrinsic primary afferent neurones are 5-HT3 mediated, 5-HT3 antagonists tend to be constipating and should be used only when pre-existing constipation is not a significant component of the problem to be treated. In contrast, 5-HT4 agonists, such as tegaserod, are safe and effective in the treatment of irritable bowel syndrome with constipation and chronic constipation. They do not stimulate nociceptive extrinsic nerves nor initiate peristaltic and secretory reflexes. Instead, they rely on natural stimuli to activate reflexes, which they strengthen by enhancing the release of transmitters in prokinetic pathways. Finally, when all the signalling by 5-HT is over, its action is terminated by uptake into enterocytes or neurones, which is mediated by the serotonin reuptake transporter. In inflammation, serotonergic signalling is specifically diminished in the mucosa. Transcripts encoding tryptophan hydroxylase-1 and serotonin reuptake transporter are both markedly decreased. Successive potentiation of 5-HT and/or desensitization of its receptor could account for the symptoms seen in diarrhoea-predominant and constipation-predominant irritable bowel syndrome, respectively. Symptoms associated with the down-regulation of the serotonin reuptake transporter in the human mucosa in irritable bowel syndrome are similar to the symptoms associated with the knockout of the serotonin reuptake transporter in mice. The observation that molecular defects occur in the human gut in irritable bowel syndrome strengthens the hand of those seeking to legitimize the disease. At least it is not 'all in your head'. The bowel contributes.

Delayed Gastric Emptying in Functional Dyspepsia

Functional dyspepsia is a complex syndrome with a poorly defined pathophysiology, resulting in uncertainties in its therapeutic approach. Abnormalities in gastrointestinal motility and sensitivity alone or combined seem to play a role in a substantial subgroup of patients. Drugs capable of prokinetic effects, such as antidopaminergics (eg, metoclopramide, domperidone, levosulpiride) and serotonin 5-HT4 receptor agonists (eg, tegaserod) can be potentially used in the treatment of dyspeptic patients. Furthermore, 5-HT4 receptor agonists do not appear to increase the gastric fundus tone which may also contribute to improved symptoms in subsets of patients. Alosetron, a 5-HT3 receptor antagonist, has been investigated mainly in irritable bowel syndrome, and the few studies performed in functional dyspepsia have provided conflicting results. Erythromycin and related derivatives, the motilides, represent another class of prokinetic compounds able to accelerate gastric emptying and potentially indicated in functional dyspepsia. The stimulatory effect on fundic tone and the occurrence of tachyphilaxis hamper the efficacy of these drugs in the long-term treatment. kappa-opioid receptor agonists might be useful for functional digestive syndromes because of their antinociceptive effects, but there are few available results and most are inconclusive. Results are also needed to prove efficacy of antidepressants (tricyclic agents and 5-HT reuptake inhibitors). Future clinical trials should be performed so that the formal structure required by good clinical practice can be adapted to detect significant effects in subgroups of patients with functional dyspepsia. Therapy should be ideally targeted to the different pathophysiologic abnormalities of these subgroups. The identification of the mechanisms leading to symptom generation should facilitate the development of newer and more effective therapeutic strategies in functional dyspepsia.

Update in the pharmaceutical therapy of the irritable bowel syndrome

The therapeutic management of the irritable bowel syndrome (IBS) is ineffective and not satisfying either patients or practitioners. Research in functions of the enteric nervous system and its interaction with the central nervous system is the basis for the development of emerging pharmaceuticals in therapy of the IBS. These pharmaceuticals include agents such as opioid agonists, psychotropic agents and particularly serotonin receptor modulators. These novel pharmaceuticals aim to provide a more comprehensive approach in the therapy of the IBS and will serve both patients and practitioners. So far, the US Food and Drug Administration has approved two agents specifically for the treatment of the IBS, both belonging to the group of serotonin receptor modulators. However, questions remain whether a single therapy is sufficient in the management of IBS because this disease is influenced by biological and psychological as well as cultural and social factors.

Irritable bowel syndrome

Irritable bowel syndrome (IBS) is one of the most common diagnoses made in the primary care setting and is responsible for up to 40% of referrals to gastroenterologists. Approximately 70% of persons who meet the diagnostic criteria for IBS do not seek health care, and the remaining account for 12% of visits to primary care providers. IBS is a functional bowel disordered comprising abdominal pain associated with defecation or a change in bowel habit with features of disordered defecation and distension in the absence of any demonstrable abnormality. The diagnosis is based on clinical findings and the exclusion of other disorders. New pharmaceutical agents are available to treat the underlying disorder; however, the treatment of IBS still involves a comprehensive, multicomponent approach that includes medical management of dominant symptoms, dietary modifications, and, possibly, psychotherapy.

Clinical pharmacokinetics of tegaserod, a serotonin 5-HT(4) receptor partial agonist with promotile activity

Tegaserod, a selective serotonin (5-hydroxytryptamine; 5-HT) 5-HT(4) receptor partial agonist, is indicated in patients with irritable bowel syndrome (IBS) who identify abdominal pain or discomfort and constipation as their predominant symptoms. Tegaserod at dosages of 1 to 12 mg/day exerts pharmacodynamic actions in the upper and the lower gastrointestinal tract, accelerating small bowel and colonic transit in patients with IBS. Tegaserod is rapidly absorbed following oral administration; peak plasma concentrations (C(max)) are reached after approximately 1 hour. Absolute bioavailability is about 10% under fasted conditions. Food reduces the bioavailability of tegaserod by 40 to 65% and the C(max) by 20 to 40%. Systemic exposure to tegaserod is not significantly altered at neutral gastric pH compared with the fasted state (pH 2). Tegaserod is approximately 98% bound to plasma proteins, primarily to alpha(1)-acid glycoprotein, and has a volume of distribution at steady-state of 368 +/- 223L. Tegaserod is metabolised mainly via two pathways. The first is a presystemic acid-catalysed hydrolysis in the stomach followed by oxidation and conjugation which produces the main metabolite of tegaserod, 5-methoxyindole-3-carboxylic acid glucuronide (M 29.0). This metabolite has negligible affinity for 5-HT(4) receptors and is devoid of promotile activity. The second is direct glucuronidation which leads to generation of three isomeric N-glucuronides. The plasma clearance of tegaserod is 77 +/- 15 L/h, with an estimated terminal half-life of 11 +/- 5 hours following intravenous administration. Approximately two-thirds of the orally administered dose of tegaserod is excreted unchanged in faeces, with the remainder excreted in urine, primarily as M 29.0. The pharmacokinetics of tegaserod are dose-proportional over the range 2 to 12mg given twice daily for 5 days, with no relevant accumulation. The pharmacokinetics of tegaserod in patients with IBS are comparable to those in healthy individuals, and similar between men and women. No dosage adjustment is required in elderly patients or those with mild to moderate hepatic or renal impairment. Tegaserod should not be used in patients with severe hepatic or renal impairment. No clinically relevant drug-drug interactions with tegaserod have been identified. In vivo drug-drug interaction studies with theophylline [a cytochrome P450 (CYP) 1A2 prototype substrate], dextromethorphan (a CYP2D6 prototype substrate), digoxin, warfarin and oral contraceptives have indicated no clinically relevant interactions and no requirement for dosage adjustment.

New developments in the treatment of functional dyspepsia

Functional dyspepsia is a clinical syndrome defined by chronic or recurrent pain or discomfort in the upper abdomen of unknown origin. Although generally accepted, investigators differently interpret this definition and clinical trials are often biased by inhomogeneous inclusion criteria. The poorly defined multifactorial pathogenesis of dyspeptic symptoms has hampered efforts to develop effective treatments. A general agreement exists on the irrelevant role played by Helicobacter pylori in the pathophysiology of functional dyspepsia. Gastric acid secretion is within normal limits in patients with functional dyspepsia but acid related symptoms may arise in a subgroup of them. Proton pump inhibitors appear to be effective in this subset of patients with dyspepsia. Non-painful dyspeptic symptoms are suggestive of underlying gastrointestinal motor disorders and such abnormalities can be demonstrated in a substantial proportion of patients. Postprandial fullness and vomiting have been associated with delayed gastric emptying of solids, and early satiety and weight loss to postcibal impaired accommodation of the gastric fundus. Prokinetics have been shown to exert beneficial effects, at least in some patients with dyspepsia. In contrast, drugs enhancing gastric fundus relaxation have been reported to improve symptoms, although conflicting results have also been published. An overdistended antrum may also generate symptoms, but its potential pathogenetic role and the effects of drugs on this abnormality have never been investigated formally. Visceral hypersensitivity plays a role in some dyspeptic patients and this abnormality is also a potential target for treatment. Both chemo- and mechanoreceptors can trigger hyperalgesic responses. Psychosocial abnormalities have been consistently found in functional digestive syndromes, including dyspepsia. Although useful in patients with irritable bowel syndromes (IBS), antidepressants have been only marginally explored in functional dyspepsia. Among the new potentially useful agents for the treatment of functional dyspepsia, serotonin 5-HT(4) receptor agonists have been shown to exert a prokinetic effect. Unlike motilides, 5-HT(4) receptor agonists do not appear to increase the gastric fundus tone and this may contribute to improve symptoms. 5-HT(3) receptor antagonists have been investigated mainly in the IBS and the few studies performed in functional dyspepsia have provided conflicting results. Also, kappa-opioid receptor agonists might be useful for functional digestive syndromes because of their antinociceptive effects, but available results in functional dyspepsia are scanty and inconclusive. Other receptors that represent potential clinical targets for antagonists include purinoceptors (i. e., P2X2/3 receptors), NMDA receptors (NR2B subtype), protease-activated receptor-2, the vanilloid receptor-1, tachykinin receptors (NK(1)/NK(2)) and cholecystokinin (CCK)(1) receptors.

Review article: bloating in functional bowel disorders

Bloating is a frequently reported symptom in functional bowel disorders. It usually occurs in combination with other symptoms, but may also occur in isolation. The severity of bloating tends to worsen during the course of the day and improves overnight. Although frequently considered to be a subjective phenomenon, recent studies have shown that bloating is associated with a measurable increase in abdominal girth. The pathophysiology of bloating remains elusive, but the evidence supports a sensorimotor dysfunction of the bowel. The possible mechanisms include abnormal gas trapping, fluid retention, food intolerance and altered gut microbial flora. Further studies are needed to define the sensorimotor abnormalities associated with bloating, which might be segmental and transient rather than generalized and persistent. The lack of understanding of this symptom is paralleled by a limited availability of therapeutic options. Conventional medications used in functional bowel disorders are not helpful and may indeed worsen the symptoms. In future, new drugs with activity against serotonin and kappa receptors, or novel approaches such as the use of exclusion diets, probiotics and hypnotherapy, may prove to be useful.

A systematic review of tegaserod for the treatment of irritable bowel syndrome

AIM

To assess the clinical effectiveness of tegaserod for the treatment of irritable bowel syndrome (IBS).

DESIGN

Systematic review.

SETTING

Six placebo-controlled, randomized controlled trials (RCTs) retrieved from electronic searches (Medline, Embase, FDA website) and hand-searching.

MAIN OUTCOME MEASURES

Any outcome was accepted.

RESULTS

In a small pharmacodynamic study, tegaserod 4 mg/day accelerated orocecal transit compared with placebo, but did not affect gastric emptying rate and colonic transit. Five placebo-controlled studies evaluated Subject's Global Assessment of gastrointestinal (GI) symptoms in predominantly female patients who fulfilled Rome criteria for constipation-predominant IBS. Responder rates were higher with tegaserod 1-24 mg/day than with placebo, although it was not possible in this review to evaluate the consistency of this effect, to fully quantify the effect size, or identify patients who may gain most benefit from this treatment.

CONCLUSION

Currently published data on tegaserod for IBS are limited (two of six RCTs published in full, four as abstracts). Tegaserod may be an appropriate treatment for occasional use for relief of GI symptoms associated with constipation-predominant IBS. Further research, comparing tegaserod with alternative treatments for GI symptoms of IBS, should help define the place of this drug in therapy.

Long-term safety of tegaserod in patients with constipation-predominant irritable bowel syndrome

BACKGROUND

Tegaserod is a 5-hydroxytryptamine-4 receptor partial agonist. Oral administration causes gastrointestinal effects resulting in increased gastrointestinal motility and attenuation of visceral sensation.

AIM

: To determine the long-term safety and tolerability of tegaserod in patients suffering from irritable bowel syndrome with constipation as the predominant symptom of altered bowel habits.

METHOD

A multicentre, open-label study with flexible dose titration of tegaserod in out-patients suffering from constipation-predominant irritable bowel syndrome.

RESULTS

A total of 579 patients with constipation-predominant irritable bowel syndrome were treated with tegaserod. Of these, 304 (53%) completed the trial. The most common adverse events, classified as related to tegaserod for any dose, were mild and transient diarrhoea (10.1%), headache (8.3%), abdominal pain (7.4%) and flatulence (5.5%). Forty serious adverse events were reported in 25 patients (4.4% of patients) leading to discontinuation in six patients. There was one serious adverse event, acute abdominal pain, classified as possibly related to tegaserod. There were no consistent differences in adverse events between patients previously exposed to tegaserod and those treated de novo. No pattern-forming tegaserod-related abnormalities in haematological and biochemical laboratory tests, urinalysis, blood pressure, pulse rate or electrocardiograms were found.

CONCLUSIONS

Tegaserod appears to be well tolerated in the treatment of patients with constipation-predominant irritable bowel syndrome. The adverse event profile, clinical laboratory evaluations, vital signs and electrocardiogram recordings revealed no evidence of any unexpected adverse events, and suggest that treatment is safe over a 12-month period.

5-Hydroxytryptamine mediated contractions in isolated preparations of equine ileum and pelvic flexure: pharmacological characterization of a new 5-HT(4) agonist

The effects of 5-hydroxytryptamine (5-HT), HTF 919, a new 5-HT(4) agonist, and the antagonists SB 203-186 (5-HT(4)) and tropisetron (5-HT(3)) on intestinal motility were tested in vitro on isolated preparations of horse ileum and pelvic flexure. Concentration-response curves were created by cumulative application of the agonists with or without preincubation of the antagonists. The 5-HT preparation induced a concentration-dependent contraction in equine ileum and pelvic flexure. The results indicate that 5-HT receptors are present in all parts of equine intestine investigated in this study. Tropisetron was found to act as a noncompetitive antagonist in all locations of the equine intestine. SB 203-106 was confirmed as an antagonist to 5-HT in the equine ileum circular muscle, in pelvic flexure circular and longitudinal muscle. Nevertheless, a discernible increase of smooth muscle contractions caused by HTF 919 could only be observed in pelvic flexure. In accordance with an earlier study in the guinea pig, in the equine gut HTF 919 acted as a partial agonist for the 5-HT(4) receptor with an affinity constant in the nanomolar range. It is concluded that 5-HT receptors, and especially their subtypes, may represent a promising target for the treatment and prevention of gastrointestinal (GI) motility disorders in horses.

Recurrent abdominal pain in children

Functional abdominal pain can occur in a well-defined clinical entity (e.g., IBS) or as a part of a poorly defined clinical syndrome. Although the clinician may feel compelled to exclude disease in all cases, the authors suggest that it is more appropriate to take a biopsychosocial approach. In so doing, there can be an appreciation of the close interaction of the gut and the brain, allowing the child, family, and physician the opportunity to address the pain on many levels. Although the parameters set forth by the pediatric ROME II committee have facilitated the authors' description of these disorders greatly, basic research likely will further delineate biochemical processes in the enteric and central nervous systems that will expand therapeutic horizons.

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.

The effects of tegaserod (HTF 919) on the pharmacokinetics and pharmacodynamics of digoxin in healthy subjects

Tegaserod (HTF 919) is a highly specific 5-HT4 receptor partial agonist that exhibits promotile activity throughout the gastrointestinal tract and is under development for the treatment of functional gastrointestinal motility disorders. The present study was designed to assess the effect of multiple doses of tegaserod on the single-dose pharmacokinetics and pharmacodynamics of digoxin, a commonly prescribed agent for congestive heart failure. The study was an open-label, randomized, two-period crossover design of 12 healthy subjects. One treatment included digoxin treatment alone; the other treatment included a combined digoxin and tegaserod treatment. On day 1 of the digoxin treatment period, subjects received a single 1 mg oral dose of digoxin. In the combined tegaserod/digoxin treatment period, subjects received a single oral dose of 1 mg digoxin after 3 days of tegaserod (6 mg bid). After coadministration of tegaserod, systemic exposure to digoxin was decreased; mean AUC decreased by 11.9% (p < 0.05) relative to digoxin alone. Cmax was decreased by about 15% (p < 0.05). The 0.5-hour difference in the median tmax between the two treatments was not statistically significant. Because the steady-state trough concentration of digoxin (C(SS,min)) correlates with pharmacological effects, C(SS,min) for digoxin alone and in combination with tegaserod was simulated based on both parametric compartmental modeling and nonparametric superpositioning approaches. The predicted arithmetic mean C(SS,min) for combination therapy is 86% to 89% of that following digoxin alone. Likewise, the predicted arithmetic mean steady-state peak concentration (C(SS,min)) and AUC at steady state during a dosing interval (AUC(SS,tau)) have a similar decrease. This extent of decrease in systemic exposure of digoxin at steady state is unlikely to be clinically relevant. Administration of tegaserod (6 mg bid) was well tolerated, both alone and in combination with a single dose of digoxin. There were no pharmacodynamic changes in ventricular rate and QT interval following coadministration of tegaserod with digoxin. The 1.5-hour and 2-hour postdose plasma concentrations of tegaserod on days 3 and 4 confirmed adequate exposure. In conclusion, dose adjustment for digoxin is unlikely to be needed when tegaserod is coadministered.

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.

Dyspepsia: challenges in diagnosis and selection of treatment

BACKGROUND

Despite considerable study, the pathophysiology of dyspepsia remains obscure. This and other factors have impeded development of precise and effective treatment strategies.

OBJECTIVE

This paper provides a brief review of the clinical syndrome of dyspepsia and its pathophysiology, symptoms, diagnosis, and treatment.

METHODS

To identify articles for inclusion in this review, a search of MEDLINE was conducted using the key word dyspepsia. Because the literature on this topic is voluminous and duplicative, the search was limited primarily to literature from the last decade and to articles concerning dyspepsia in adults.

RESULTS

The symptoms of dyspepsia, which may include epigastric pain, heartburn. bloating, and early satiety, defy diagnosis in as many as 50% of patients, even after endoscopy and other appropriate studies. In the other half of patients, such causative disorders as gastroesophageal reflux disease (GERD), peptic ulcer disease, cholecystitis, pancreatitis, and gastric cancer may be diagnosed. Despite controversy regarding the selection of therapy, empiric treatment is common for apparent idiopathic dyspepsia. Histamine2-receptor antagonists, proton pump inhibitors (PPIs), promotility agents, and coating agents have all been used as empiric therapy for dyspeptic symptoms. With empiric treatment, subsequent management is directed by the therapeutic response. In the absence of a definitive diagnosis, treatment is usually selected on the basis of the type and severity of symptoms, a thorough history and physical examination, and factors such as age and the presence of Helicobacter pylori infection. Five PPIs are currently available--lansoprazole, omeprazole, rabeprazole, pantoprazole, and esomeprazole--all with established efficacy in GERD and other acid-mediated disorders. The PPIs can be expected to be useful in certain patients with dyspepsia, and may be prescribed for patients who are found to re- spond to potent antisecretory therapy. Patients' concern about their symptoms, practical considerations, and restrictions imposed by managed care organizations may all affect the choice between empiric therapy and early endoscopy in patients with dyspepsia.

CONCLUSIONS

Despite the variety of therapeutic options available for the symptoms of dyspepsia, the many presentations of this condition and the uncertainty of the response to the currently available therapeutic options continue to pose a substantial clinical challenge.

The pharmacokinetics of the novel promotile drug, tegaserod, are similar in healthy subjects-male and female, elderly and young

BACKGROUND

Tegaserod (HTF 919) is a selective 5-HT4 receptor partial agonist in development for the treatment of irritable bowel syndrome.

AIM

This study aimed to assess the effect of age and gender on the single-dose pharmacokinetics of tegaserod.

METHODS

In a parallel-group, open-label study, a single dose of tegaserod (12 mg) was administered to four groups of healthy young male, young female, elderly male and elderly female subjects (n=10 per group). Blood samples were collected from 0 to 24 h postdose. Non-compartmental pharmacokinetics evaluation and statistical analysis (ANOVA and Wilcoxon signed ranks test for tmax) were performed.

RESULTS

Tegaserod was well tolerated in all groups. There was no effect of age or gender on tmax and Cmax. Gender did not affect AUC0-infinity and AUC0-tz; there was a statistically significant effect of age on these parameters. AUC0-infinity and AUC0-tz in the elderly were greater than in the young (AUC0-infinity ratio 1.37, P < 0.001; AUC0-tz ratio 1.23, P=0.029). This increase in exposure is judged not to be clinically relevant because it is within the variability in the pharmacokinetics parameters of tegaserod and because the dose-response relationship of tegaserod is relatively shallow.

CONCLUSIONS

No dose adjustment for age or gender is recommended in tegaserod therapy.

Constipation and fecal incontinence in the elderly

Although constipation and fecal incontinence are common symptoms in the elderly, relatively little research has been done to differentiate physiologic changes in rectoanal function resulting from aging and pathologic changes resulting from diseases occurring as patients age. Certain physiologic changes occur in many older patients and may predispose them to the development of constipation or fecal incontinence. These symptoms need the same thoughtful evaluation and management in the elderly as in younger patients. Results of therapy often can be good, leading to alleviation of suffering and the ability to lead a fuller life.

Irritable bowel syndrome: new agents targeting serotonin receptor subtypes

Although the past few years have seen an exponential growth of compounds of potential interest for the treatment of functional gastrointestinal (GI) tract disorders, the gap that still exists between basic and clinical research is easily noticed if one considers the relative paucity of drugs that have received marketing authorisation for the treatment of irritable bowel syndrome (IBS). Traditional efficacy outcomes in drug development for IBS include the ability of the compound to affect GI tract motility (i.e. to exert a prokinetic or an antispasmodic effect), which is thought to be of importance if a motor disorder is the underlying pathophysiological mechanism. More recently, altered visceral sensitivity to a distending stimulus has been suggested to be a key pathophysiological feature, at least in some patients, and has become a target for therapeutic interventions. However, there is now growing consensus that the primary outcome measure in the treatment of functional disorders are those that reflect overall control of the patient's symptoms (pain, diarrhoea, constipation) in everyday situations such as the clinical global improvement scales. Although, in general, guidelines on the design of treatment trials for functional GI tract disorders advise against subcategorisation of patients according to the main symptom (because of symptom instability), subcategorisation indeed makes sense especially in IBS (constipation- or diarrhoea-predominant). Compounds with a specific indication for each subpopulation of patients are now emerging. The rationale for investigations on serotonin (5-hydroxytryptamine; 5-HT) receptor ligands in IBS rests mainly on the fact that serotonin, which may be released by enterochromaffin-like cells in the GI tract as well as from other sources, has a number of well documented motor effects on the GI tract and can produce hyperalgesia in several experimental models. Serotonin receptors belonging to the 5-HT3 and 5-HT4 subtype are the most extensively studied in gastroenterology, although hitherto 'orphan' receptor subtypes, such as the 5-HT7 and the 5-HT(1B/D) receptors, are now emerging. Among 5-HT3 receptor antagonists, alosetron was recently approved for the treatment of diarrhoea-predominant IBS and is an example of a compound that, at least theoretically, may act at multiple levels: by inhibiting visceral sensitivity, by increasing compliance, and by inhibiting excitatory 5-HT3 receptors located on both ascending and descending neuronal pathways involved in peristalsis. For this reason, 5-HT3 receptor antagonists may slow transit, hence the specific indication of alosetron in diarrhoea-predominant IBS. However, alosetron has been recently withdrawn by the manufacturer because of safety concerns. Hypomotility remains an attractive therapeutic target in IBS and the new generation of prokinetics includes several partial agonists at the 5-HT4 receptor, such as tegaserod (HTF-919) and prucalopride (R0-93877). In addition, preliminary evidence suggests that 5-HT4 receptors may also be involved in the modulation of visceral sensitivity. Second-generation 5-HT4 receptor agonists seem to be devoid of the QT-prolonging effects observed in some clinical circumstances with cisapride and may be more active at the colonic level. Piboserod (SB-207266A) is a 5-HT4 receptor antagonist under development for the treatment of diarrhoea-predominant IBS. Finally, interest in 5-HT7 and 5-HT(1B/D) receptor subtypes stems from the observation that the former receptors mediate smooth muscle relaxation (at least in the human colon), whereas sumatriptan (a 5-HT(1B/D) receptor agonist) can affect GI tract motility and visceral sensitivity.

Gastrointestinal functional bowel disorders: new therapies

Present therapies for functional gastrointestinal disorders are symptomatic and mainly treat altered bowel habits. New therapies are focused on nerve-gut communication dysfunction: 5-HT3 antagonists and 5-HT4 agonists have demonstrated activity in clinical trials. Promising targets for upper gut dysmotility drugs are motilin and cholecystokinin A receptors. Tachykinins, calcitonin gene-related peptide or glutamate antagonists are the most relevant candidates for visceral pain.