Systematic review: cardiovascular safety profile of 5-HT(4) agonists developed for gastrointestinal disorders

Novel gut-restricted bivalent agonists targeting mucosal 5-HT4R: Design, synthesis, and biological evaluation

Chronic idiopathic constipation (CIC) is a prevalent gastrointestinal disorder with limited therapeutic options that balance efficacy and safety. Current therapies, such as the 5-HT4 receptor (5-HT4R) agonist prucalopride, demonstrate efficacy but are often associated with systemic side effects, highlighting the need for gut-restricted alternatives. Herein, we report for the first time the rational design and synthesis of gut-restricted bivalent agonists targeting mucosal 5-HT4R by integrating pharmacophores of prucalopride and tenapanor. Structural optimization, particularly of linker length and properties, led to the discovery of compound 4, which exhibited potent 5-HT4R agonistic activity, high selectivity, and favorable physicochemical properties. Preclinical studies demonstrated that compound 4 significantly enhanced whole-gut and colonic transit, increased fecal output and water content, while maintaining minimal systemic absorption, confirming its gut-restricted nature. These findings underscore the feasibility of gut-restricted 5-HT4R agonists as a novel therapeutic strategy for CIC and provide valuable insights into the development of safer, more effective treatments for gastrointestinal disorders.

2025 Seoul Consensus on Clinical Practice Guidelines for Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a chronic, disabling, and functional bowel disorder that significantly affects social functioning and reduces quality of life and increases social costs. The Korean Society of Neurogastroenterology and Motility published clinical practice guidelines on the management of IBS based on a systematic review of the literature in 2017, and planned to revise these guidelines in light of new evidence on the pathophysiology, diagnosis, and management of IBS. The current revised version of the guidelines is consistent with the previous version and targets adults diagnosed with or suspected of having IBS. These guidelines were developed using a combination of de novo and adaptation methods, with analyses of existing guidelines and discussions within the committee, leading to the identification of key clinical questions. Finally, the guidelines consisted of 22 recommendations, including 3 concerning the definition and risk factors of IBS, 4 regarding diagnostic modalities and strategies, 2 regarding general management, and 13 regarding medical treatment. For each statement, the advantages, disadvantages, and precautions were thoroughly detailed. The modified Delphi method was used to achieve expert consensus to adopt the core recommendations of the guidelines. These guidelines serve as a reference for clinicians (including primary care physicians, general healthcare providers, medical students, residents, and other healthcare professionals) and patients, helping them to make informed decisions regarding IBS management.

Psychiatric Adverse Effects From Prucalopride in a Medically Complex Adolescent

Background: Prucalopride is a highly selective, 5-HT4 receptor agonist that can be used for the treatment of chronic constipation in individuals for whom laxatives fail to provide adequate relief. The current case study describes adverse neuropsychiatric symptoms following the administration of prucalopride in a 15-year-old female with a complex physical and mental health history to manage chronic constipation. Case Summary: A single 2 mg dose of prucalopride was prescribed to a 15-year-old female to manage her chronic constipation due to a diagnosis of autoimmune enteric neuropathy. Following the oral administration of prucalopride, the patient started experiencing visual and auditory hallucinations, along with suicidal ideation. Prucalopride was ceased, with the patient receiving psychopharmacology and psychological intervention to address the acute onset psychiatric symptoms. Practical Implications: To our knowledge, this is the second documented case of acute onset neuropsychiatric symptoms following the administration of prucalopride. Clinicians should be aware of this possible side effect, particularly if considering administering prucalopride in patients with neurodevelopmental and psychiatric comorbid histories. Increased supervision and monitoring is recommended in these patients if prucalopride is administrated.

Clebopride stimulates 5-HT4-serotonin receptors in the human atrium

Clebopride resembles in its structural formula metoclopramide. Clebopride, an approved drug, is used to treat gastrointestinal diseases. Here, we tested the hypothesis that clebopride like metoclopramide acts as a partial agonist at human cardiac 5-HT4-serotonin-receptors. Clebopride enhanced the force of contraction (FOC) in isolated, electrically stimulated (1 Hz) left atrial preparations (LA) from transgenic mice with cardiac specific overexpression of the human 5-HT4-serotonin receptors (5-HT4-TG). Subsequently applied GR125487 (1 µM), a specific 5-HT4-serotonin-receptor antagonist, diminished this positive inotropic effect (PIE) of clebopride in LA from 5-HT4-TG. Clebopride failed to heighten FOC in LA from littermate wild-type mouse hearts (WT). Clebopride augmented the beating rate in isolated right atrial preparations (RA) from 5-HT4-TG but unable to do so in RA from WT. Clebopride alone (up to 10 µM) failed to augment FOC in isolated electrically stimulated (1Hz) human right atrial preparations (HAP) obtained during open heart surgery from adult patients with severe coronary heart disease. Interestingly, in the presence of the phosphodiesterase III inhibitor cilostamide, clebopride heightened FOC in HAP. GR125487 attenuated this PIE in HAP. Furthermore, when 1 µM serotonin had raised FOC in HAP, additionally applied 10 µM clebopride diminished FOC in HAP. We conclude that clebopride can act as an agonist and as an antagonist at 5-HT4-serotonin receptors in the human atrium.

Pharmacologic treatments for gastroparesis

Gastroparesis is a neurogastrointestinal disorder of motility in which patients experience symptoms of nausea, vomiting, bloating, early satiety, postprandial fullness, upper abdominal discomfort or pain, and delayed gastric emptying of solids based on scintigraphy or stable isotope breath test when mechanical obstruction has been excluded. Symptoms of gastroparesis may result from diverse pathophysiological mechanisms, including antroduodenal hypomotility, pylorospasm, increased gastric accommodation, and visceral hypersensitivity. The most common etiologies of gastroparesis are idiopathic, diabetic, and postsurgical, and less frequent causes are neurodegenerative disorders (Parkinson's disease), myopathies (scleroderma, amyloidosis), medication-induced (glucagon-like peptide-1 agonists and opioid agents), and paraneoplastic syndrome. This review addresses pharmacologic management of gastroparesis including prokinetic and antiemetic agents, pharmacologic agents targeting the pylorus, and effects of neuromodulators. SIGNIFICANCE STATEMENT: Gastroparesis is a neurogastrointestinal motility disorder characterized by delayed gastric emptying without mechanical obstruction with numerous upper gastrointestinal symptoms, including nausea and vomiting. The management of gastroparesis involves nutritional support, medications, and procedures. The only Food and Drug Administration-approved medication for gastroparesis is metoclopramide. This article reviews the pharmacology and efficacy of all classes of antiemetics or prokinetic effects used in gastroparesis. There is still a considerable unmet need for efficacious medications specifically for the treatment of gastroparesis, especially in refractory cases.

Rome Foundation and international neurogastroenterology and motility societies' consensus on idiopathic gastroparesis

To establish a consensus on the definition and management of idiopathic gastroparesis, international experts (selected by neurogastroenterology and motility societies and initiated by the Rome Foundation) devised 144 statements using the Delphi method, with at least 80% agreement required. This consensus defined idiopathic gastroparesis as the presence of symptoms associated with delayed gastric emptying in the absence of mechanical obstruction. Nausea and vomiting were identified as cardinal symptoms. Frequently co-existing symptoms are early satiation and postprandial fullness. Diagnosis requires the presence of these symptoms alongside delayed gastric emptying, measured by a 4 h scintigraphy or gastric emptying breath test of a mixed composition meal in the absence of mechanical obstruction. Therapeutic options with proven efficacy were sparse. Dietary adjustments, nutritional support (per guidelines from the European Society for Clinical Nutrition and Metabolism for substantial weight loss or intractable vomiting), and opioid cessation were recommended by a consensus opinion. Antiemetic and prokinetic agents were also considered potentially beneficial. This consensus offers a global perspective on idiopathic gastroparesis.

Efficacy and safety of prucalopride in patients with chronic idiopathic constipation stratified by age, body mass index, and renal function: a post hoc analysis of phase III and IV, randomized, placebo-controlled clinical studies

Background

Prucalopride (1 or 2 mg once daily) is approved for treating adults with chronic idiopathic constipation (CIC).

Objectives

We determined the effect of age, body mass index (BMI), and renal function on the efficacy and safety of prucalopride in adults with CIC.

Design

Data were pooled from six 12-week, phase III-IV clinical studies in adults who received prucalopride (1 or 2 mg once daily) or placebo for CIC.

Methods

Adults were stratified by age (<50; 50-64; ⩾65 years), BMI (underweight/healthy weight, <25 kg/m2; overweight, 25 to <30 kg/m2; obese, ⩾30 kg/m2), and renal function (normal renal function, estimated glomerular filtration rate (eGFR) ⩾90 mL/min/1.73 m2; mild renal impairment, eGFR 60 to <90 mL/min/1.73 m2; moderate renal impairment, eGFR 30 to <60 mL/min/1.73 m2). The primary efficacy endpoint was the proportion of patients with a mean of ⩾3 complete spontaneous bowel movements/week over 12 weeks. Safety data were evaluated descriptively.

Results

Of 2484 patients stratified by age (prucalopride, n = 1237; placebo, n = 1247), 1402, 708, and 374 were aged <50, 50-64, and ⩾65 years, respectively. Of 2482 patients stratified by BMI (prucalopride, n = 1237; placebo, n = 1245), 1425, 713, and 344 were underweight/healthy weight, overweight, and obese, respectively. Of 2474 patients stratified by renal function (prucalopride, n = 1233; placebo, n = 1241), 1444, 869, and 161 had normal renal function, mild renal impairment, and moderate renal impairment, respectively. More prucalopride-treated than placebo-treated patients achieved the primary efficacy endpoint. The difference was significant for all subgroups, except for the obese and moderate renal impairment subgroups. More prucalopride-treated than placebo-treated patients reported treatment-related adverse events in most subgroups.

Conclusion

Prucalopride demonstrated efficacy in adults with CIC, irrespective of age, BMI, and renal function. No unexpected safety concerns were identified.

Trial registration

ClinicalTrials.gov identifiers (https://clinicaltrials.gov/): NCT01147926, NCT01424228, NCT01116206, NCT00483886, NCT00485940, NCT00488137.

Personalisation of therapy in irritable bowel syndrome: a hypothesis

Irritable bowel syndrome (IBS) is a common disorder of gut-brain interaction characterised by symptoms of abdominal pain, occurring at least 1 day per week, and a change in stool frequency or form. Individuals with IBS are usually subtyped according to their predominant bowel habit, which is used to direct symptom-based treatment. However, this approach is probably an oversimplification of a complex and multidimensional condition, and other factors, such as psychological health, are known to influence symptom severity and prognosis. We have previously used latent class analysis, a method of mathematical modelling, to show that people with IBS can be classified into seven unique clusters based on a combination of gastrointestinal symptoms, abdominal pain, extraintestinal symptoms, and psychological comorbidity. The clusters can be used to predict the prognosis of IBS (eg, symptom severity), health-care use (eg, consultation behaviour, prescribing, and costs), and impact (eg, quality of life, work and productivity, activities of daily living, and income). These clusters could also be used to increase the personalisation of IBS treatment that better recognises the heterogenous nature of the condition. We present new data providing additional validation of our seven-cluster model and conduct a comprehensive evidence-based review of IBS management. Based on this evidence, we propose a framework of first-line and second-line treatments according to IBS cluster. Finally, we discuss what further research is needed to implement this approach in clinical practice, including the need for randomised trials comparing cluster-based treatment with conventional treatment according to stool subtype.

Tegaserod Stimulates 5-HT4 Serotonin Receptors in the Isolated Human Atrium

Tegaserod (1-{[(5-methoxy-1H-indol-3-yl)methyliden]amino}-3-pentylguanidine) is a potent agonist at human recombinant 5-HT4 serotonin receptors. Consequently, tegaserod is utilized in the treatment of bowel diseases. The objective of this study was to test the hypothesis that tegaserod stimulates human cardiac atrial 5-HT4-receptors via cyclic adenosine monophosphate (cAMP)-dependent pathways. Tegaserod exerted positive inotropic effects (PIEs) and positive chronotropic effects (PCEs) in isolated left and right atrial preparations, respectively, from mice with cardiac-specific overexpression of the human 5-HT4 serotonin receptor (5-HT4-TG) in a concentration- and time-dependent manner. However, no effect was observed in the hearts of littermates of wild-type mice (WT). Western blot analysis revealed that the expression of 5-HT4 receptors was significantly higher in 5-HT4-TG mice compared to WT mice. The specificity of the signal for the 5-HT4 receptor was confirmed by the absence of the signal in the hearts of 5-HT4 receptor knockout mice. Furthermore, tegaserod increased the force of contraction (at concentrations as low as 10 nM), reduced the time of tension relaxation, and increased the rate of tension development in isolated electrically stimulated (at a rate of 60 beats per minute) human right atrial preparations (HAPs, obtained during open-heart surgery) when administered alone. The potency and efficacy of tegaserod to raise the force of contraction were enhanced in the presence of cilostamide, a phosphodiesterase III inhibitor. The positive inotropic effect of tegaserod in HAPs was found to be attenuated by the 5-HT4 serotonin receptor antagonist GR 125487 (0.1 µM). The efficacy of tegaserod (10 µM) in raising the force of contraction in HAPs was less pronounced than that of serotonin (10 µM) or isoprenaline (1 µM). Tegaserod shifted the concentration-response curve of the force of contraction to serotonin to the right in HAPs, indicating that it is a partial agonist at 5-HT4 serotonin receptors in this model. We propose that the mechanism of action of tegaserod in HAPs involves cAMP-dependent phosphorylation of cardiac regulatory proteins.

Irritable Bowel Syndrome: Current Landscape of Diagnostic Guidelines and Therapeutic Strategies

Irritable bowel syndrome (IBS) is a disorder of the gut–brain axis with pronounced adverse effects on physical health, psychological health, and overall quality of life. Diagnostic strategies can vary, highlighting a need to synthesize best-practice guidelines. Particularly, the American College of Gastroenterology and the British Society of Gastroenterology both support a positive diagnostic strategy; evaluation with C-reactive protein, fecal calprotectin, and fecal lactoferrin; and evaluation with celiac disease serology. Both guidelines do not support routine colonoscopy, and both differ in recommendations for anorectal physiology testing. Given there is currently no curative treatment available, IBS management focuses on symptomatic relief, and challenges exist in achieving and maintaining this relief. Many treatments, both pharmacologic and nonpharmacologic, exist to alleviate the uncomfortable, painful symptoms of the disorder; however, stratifying the quality of evidence behind each option is critical for application to clinical management and for tailoring this management to each patient. Lifestyle adjustments, especially in relation to diet, can be effective first-line therapies and supplements to pharmacologic therapy. Pharmacologic treatment is broadly categorized in accordance with the subtypes of IBS, with indications for different populations and mechanisms that work to target components of IBS pathophysiology. The aim of this article is to comprehensively compare updated diagnostic guidelines, review standard treatments, and outline recent pharmacologic advancements.

Mosapride stimulates human 5-HT4-serotonin receptors in the heart

Mosapride (4-amino-5-chloro-2-ethoxy-N-[[4-[(4-fluorophenyl) methyl]-2-morpholinyl]-methyl] benzamide) is a potent agonist at gastrointestinal 5-HT4 receptors. Mosapride is an approved drug to treat several gastric diseases. We tested the hypothesis that mosapride also stimulates 5-HT4 receptors in the heart. Mosapride increased the force of contraction and beating rate in isolated atrial preparations from mice with cardiac overexpression of human 5-HT4-serotonin receptors (5-HT4-TG). However, it is inactive in wild-type mouse hearts (WT). Mosapride was less effective and potent than serotonin in raising the force of contraction or the beating rate in 5-HT4-TG. Only in the presence of cilostamide (1 μM), a phosphodiesterase III inhibitor, mosapride, and its primary metabolite time dependently raised the force of contraction under isometric conditions in isolated paced human right atrial preparations (HAP, obtained during open heart surgery). In HAP, mosapride (10 μM) reduced serotonin-induced increases in the force of contraction. Mosapride (10 µM) shifted the concentration-response curves to serotonin in HAP to the right. These data suggest that mosapride is a partial agonist at 5-HT4-serotonin receptors in HAP.

Therapeutic potential of allosteric modulators for the treatment of gastrointestinal motility disorders

Gastrointestinal motility is tightly regulated by the enteric nervous system (ENS). Disruption of coordinated enteric nervous system activity can result in dysmotility. Pharmacological treatment options for dysmotility include targeting of G protein-coupled receptors (GPCRs) expressed by neurons of the enteric nervous system. Current GPCR-targeting drugs for motility disorders bind to the highly conserved endogenous ligand-binding site and promote indiscriminate activation or inhibition of the target receptor throughout the body. This can be associated with significant side-effect liability and a loss of physiological tone. Allosteric modulators of GPCRs bind to a distinct site from the endogenous ligand, which is typically less conserved across multiple receptor subtypes and can modulate endogenous ligand signalling. Allosteric modulation of GPCRs that are important for enteric nervous system function may provide effective relief from motility disorders while limiting side-effects. This review will focus on how allosteric modulators of GPCRs may influence gastrointestinal motility, using 5-hydroxytryptamine (5-HT), acetylcholine (ACh) and opioid receptors as examples. LINKED ARTICLES: This article is part of a themed issue Therapeutic Targeting of G Protein-Coupled Receptors: hot topics from the Australasian Society of Clinical and Experimental Pharmacologists and Toxicologists 2021 Virtual Annual Scientific Meeting. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.14/issuetoc.

Gastroparesis treatment options metoclopramide and prucalopride: analysis of the FDA Adverse Event Reporting System (FAERS) database

BACKGROUND

We aimed to examine the common adverse drug reactions (ADRs) of metoclopramide, FDA-approved for treating many gastrointestinal conditions including gastroparesis, and prucalopride, FDA-approved for treating chronic idiopathic constipation but used off-label for other gastrointestinal conditions including gastroparesis.

RESEARCH DESIGN AND METHODS

The FDA Adverse Event Reporting System (FAERS) was analyzed from January 2013 to December 2023. ADR reports regarding use of only metoclopramide or prucalopride were analyzed following exclusion of reports indicating use for treatment of non-gastrointestinal conditions.

RESULTS

Analysis of 1,085 reports on metoclopramide revealed tardive dyskinesia (n = 393, 36.2%) and dystonia (n = 170, 15.7%) among the most reported ADRs in addition to QTc prolongation (n = 16, 1.5%) with progression to Torsade de pointes (n = 5, 0.5%) and triggering of pheochromocytoma crisis (n = 24, 2.2%). Analysis of 865 reports on prucalopride revealed headache (n = 120, 13.9%), diarrhea (n = 116, 13.4%), and abdominal pain (n = 100, 11.6%) as the most common ADRs with 22 reports (2.5%) of dystonia with the use of prucalopride.

CONCLUSIONS

This FAERS database analysis shows post-marketing reports of ADRs from metoclopramide most frequently include tardive dyskinesia, dystonia, and tremor in addition to potentially fatal arrhythmias such as Torsade de pointes. Consumers of prucalopride may also be at risk of dystonia and other ADRs.

Prokinetics-safety and efficacy: The European Society of Neurogastroenterology and Motility/The American Neurogastroenterology and Motility Society expert review

BACKGROUND

Prokinetics are a class of pharmacological drugs designed to improve gastrointestinal (GI) motility, either regionally or across the whole gut. Each drug has its merits and drawbacks, and based on current evidence as high-quality studies are limited, we have no clear recommendation on one class or other. However, there remains a large unmet need for both regionally selective and/or globally acting prokinetic drugs that work primarily intraluminally and are safe and without systemic side effects.

PURPOSE

Here, we describe the strengths and weaknesses of six classes of prokinetic drugs, including their pharmacokinetic properties, efficacy, safety and tolerability and potential indications.

Current and emerging pharmacotherapy for the treatment of gastroparesis

INTRODUCTION

Gastroparesis is a chronic disorder characterized by decreased gastric emptying and presents with nausea, vomiting, and abdominal pain which impacts patients' quality of life greatly. The treatment modalities available for gastroparesis have been expanding over the past 2 decades. Currently, there are multiple options available for gastroparesis, albeit with only one FDA-approved medication until June 2021.

AREAS COVERED

We review the different treatments available for gastroparesis and discuss the recently FDA-approved intranasal formulation of metoclopramide. This nasal spray guarantees metoclopramide absorption within 15 min of application bypassing first pass metabolism in the liver and overcoming the limitations of the oral formulation not passing into the small intestine for absorption because of a gastroparetic stomach or a patient unable to take the oral metoclopramide because of nausea and vomiting.

EXPERT OPINION

We now find ourselves in an oasis after spending many years in a 'desert' regarding pharmacologic therapies available for gastroparesis. The expansion of the research involving dopamine receptor antagonists and delving into alternative mechanisms of alleviating gastroparesis symptoms has been crucial in the landscape of gastroparesis. This is especially true as our knowledge of gastroparesis has proven that simply improving gastric emptying does not necessarily translate to clinical improvement.

Safety and Effectiveness of Prucalopride in Children with Functional Constipation with and without Upper Symptoms

INTRODUCTION

Pediatric prucalopride studies for treatment of gastrointestinal (GI) disorders have reported mixed results. We aimed to assess the safety and effectiveness of prucalopride in functional constipation (FC) with and without upper GI symptoms.

METHODS

Retrospective data on patients with FC receiving combined prucalopride and conventional therapy was compared with those receiving conventional therapy alone within 12 months. Thirty patients on combined therapy and those on conventional therapy were each matched on the basis of age, gender, race, and presence of fecal soiling. Response (complete, partial, or no resolution) was compared. Similarly, response to concurrent functional upper GI symptoms (postprandial pain, bloating, weight loss, vomiting, early satiety, or nausea) and dysphagia, as well as adverse effects, were evaluated in the combined group.

RESULTS

Mean age of 57 cases was 14.7 ± 4.9 years and 68% were female. Comorbidities included functional upper GI (UGI) symptoms (84%), dysphagia (12%), mood disorders (49%), and hypermobility spectrum disorder (37%). Unmatched cases reported 63% improvement to FC; response did not differ between the matched cohorts (70% versus 76.6%, p = 0.84). Cases showed a 56% improvement in functional UGI symptoms and 100% in dysphagia. Adverse effects were reported in 30%, abdominal cramps being most common. Four (7%) patients with a known mood disorder reported worsened mood, of which two endorsed suicidal ideation.

CONCLUSION

Prucalopride efficaciously treated concurrent UGI symptoms and dysphagia in constipated pediatric patients and was overall well tolerated. Preexisting mood disorders seemed to worsen in a small subset of cases.

Protective actions of a luminally acting 5-HT4 receptor agonist in mouse models of colitis

BACKGROUND

5-hydroxytryptamine 4 receptors (5-HT4 Rs) are expressed in the colonic epithelium, and previous studies have demonstrated that luminal administration of agonists enhances motility, suppresses nociception, and is protective in models of inflammation. We investigated whether stimulation with a luminally acting 5-HT4 R agonist is comparable to previously tested absorbable compounds.

METHODS

The dextran sodium sulfate (DSS), trinitrobenzene sulfonic acid (TNBS), and interleukin 10 knockout (IL-10KO) models of colitis were used to test the protective effects of the luminally acting 5-HT4 R agonist, 5HT4-LA1, in the absence and presence of a 5-HT4 R antagonist. The compounds were delivered by enema to mice either before (prevention) or after (recovery) the onset of active colitis. Outcome measure included disease activity index (DAI) and histological evaluation of colon tissue, and effects on wound healing and fecal water content were also assessed.

KEY RESULTS

Daily enema of 5HT4-LA1 attenuated the development of, and accelerated recovery from, active colitis. Enema administration of 5HT4-LA1 did not attenuate the development of colitis in 5-HT4 R knockout mice. Stimulation of 5-HT4 Rs with 5HT4-LA1 increased Caco-2 cell migration (accelerated wound healing). Daily administration of 5HT4-LA1 did not increase fecal water content in active colitis.

CONCLUSIONS AND INFERENCES

Luminally restricted 5-HT4 R agonists are comparable to absorbable compounds in attenuating and accelerating recovery from active colitis. Luminally acting 5-HT4 R agonists may be useful as an adjuvant to current inflammatory bowel disease (IBD) treatments to enhance epithelial healing.

Trends in Gastroparesis Management: A United States Population-based Study From 2010 to 2020

BACKGROUND

There is little consensus on the medical management of gastroparesis, a disorder characterized by delayed gastric emptying with symptoms of early satiety, nausea, vomiting, and upper abdominal pain.

GOALS

We utilized population-level data to: (1) describe the prevalence of different pharmacological and nonpharmacological therapies in patients with gastroparesis; and (2) trend the prevalence of these therapies from 2010 to 2020.

STUDY

More than 59 million unique medical records across 26 US-based major health care systems were surveyed using the Explorys platform to identify a cohort of adults with gastroparesis who completed both a gastric emptying study and upper endoscopy or upper gastrointestinal tract imaging. Prevalence of antiemetic, prokinetic, neuromodulator prescriptions, and surgical therapies for gastroparesis were searched within this cohort and trended annually from 2010 to 2020.

RESULTS

Antiemetics (72% of patients), prokinetics (47%), and neuromodulators (75% of patients, 44% of patients without a concomitant psychiatric or diabetic peripheral neuropathy diagnosis) were all commonly used in the treatment of patients with gastroparesis. From 2010 to 2020, there was an increase in the prevalence of antiemetic and neuromodulator prescriptions (36.4% to 57.6%, P <0.001 and 47.0% to 66.9%, P <0.001, respectively), whereas the prevalence of prokinetics remained relatively constant (31.8% to 31.6%, P =0.52). Procedural and surgical treatments were used in 5% of gastroparesis patients.

CONCLUSIONS

Treatments for gastroparesis have changed over the last decade: antiemetic and neuromodulator use has increased whereas prokinetic use has remained constant. This practice pattern may reflect the growing number and availability of antiemetics and neuromodulators and the small number and known side effects of prokinetics.

Paracrine relationship between incretin hormones and endogenous 5-hydroxytryptamine in the small and large intestine

BACKGROUND

Enterochromaffin (EC) cell-derived 5-hydroxytryptamine (5-HT) is a mediator of toxin-induced reflexes, initiating emesis via vagal and central 5-HT3 receptors. The amine is also involved in gastrointestinal (GI) reflexes that are prosecretory and promotile, and recently 5-HT's roles in chemosensation in the distal bowel have been described. We set out to establish the efficacy of 5-HT signaling, local 5-HT levels and pharmacology in discrete regions of the mouse small and large intestine. We also investigated the inter-relationships between incretin hormones, glucagon-like peptide-1 (GLP-1) and gastric inhibitory polypeptide (GIP) and endogenous 5-HT in mucosal and motility assays.

METHODS

Adult mouse GI mucosae were mounted in Ussing chambers and area-specific studies were performed to establish the 5-HT3 and 5-HT4 pharmacology, the sidedness of responses, and the inter-relationships between incretins and endogenous 5-HT. Natural fecal pellet transit in vitro and full-length GI transit in vivo were also measured.

KEY RESULTS

We observed the greatest level of tonic and exogenous 5-HT-induced ion transport and highest levels of 5-HT in ascending colon mucosa. Here both 5-HT3 and 5-HT4 receptors were involved but elsewhere in the GI tract epithelial basolateral 5-HT4 receptors mediate 5-HT's prosecretory effect. Exendin-4 and GIP induced 5-HT release in the ascending colon, while L cell-derived PYY also contributed to GIP mucosal effects in the descending colon. Both peptides slowed colonic transit.

CONCLUSIONS & INFERENCES

We provide functional evidence for paracrine interplay between 5-HT, GLP-1 and GIP, particularly in the colonic mucosal region. Basolateral epithelial 5-HT4 receptors mediated both 5-HT and incretin mucosal responses in healthy colon.

Targeting the altered duodenal microenvironment in functional dyspepsia

Duodenal micro-inflammation and microbial dysregulation are increasingly recognized to play an important role in functional dyspepsia (FD) pathophysiology, previously regarded as a purely functional disorder. With current therapeutic options contested through insufficient efficacy or unfavorable adverse effects profiles, novel treatments directed to duodenal alterations could result in superior symptom control in at least a subset of patients. Indeed, recent advances in FD research provided evidence for anti-inflammatory therapies to relieve gastroduodenal symptoms by reducing duodenal eosinophils or mast cells. In addition, restoring microbial homeostasis by probiotics proved to be successful in FD. As the exact mechanisms by which these novel pharmacological approaches result in clinical benefit often remain to be elucidated, future research should focus on how immune activation and dysbiosis translate into typical FD symptomatology.

Gastroparesis and Functional Dyspepsia: Spectrum of Gastroduodenal Neuromuscular Disorders or Unique Entities?

Gastroparesis is defined by delayed gastric emptying in the absence of mechanical obstruction of the stomach. Patients experience symptoms of nausea, vomiting, abdominal pain, fullness, and early satiety. The recognition of the disorder has progressed due to availability of gastric emptying scintigraphy and advancements made in understanding its pathophysiology and treatment options. The clinical presentation and treatment of gastroparesis overlap with a more commonly recognized disorder of gut-brain interaction, functional dyspepsia. Recent studies have reenergized the discussion whether these two are separate entities or perhaps reflect a spectrum of gastroduodenal neuromuscular disorders. The societal guidelines conflict on the utility of gastric emptying scintigraphy in assessment of patients with upper gastrointestinal symptoms. A better appraisal of similarities and differences between gastroparesis and functional dyspepsia will allow targeted treatment for these disorders. This is particularly important as specific pharmacological and endoscopic treatment options are being developed for gastroparesis which are unlikely to be helpful for functional dyspepsia. This review makes the case for considering these disorders in a spectrum where identification of both would most ideally position us toward providing the optimal clinical care.

Tegaserod: What's Old Is New Again

Irritable bowel syndrome with constipation (IBS-C) and chronic idiopathic constipation (CIC) are common gastrointestinal disorders imposing considerable impact on the quality of life and well-being of affected individuals. A paucity of evidence-based treatment options exist for CIC and IBS-C sufferers. Tegaserod, a 5-HT₄ agonist, has a substantial body of preclinical and clinical study evidence to support its beneficial role in modulating sensorimotor function of the luminal gastrointestinal tract. Tegaserod was first approved for use by the U.S. Food and Drug Administration for the management of IBS-C and CIC in 2002 and 2004, respectively. Tegaserod enjoyed a successful uptake in the management of these disorders during its first several years of availability in the United States, but was later withdrawn from the market in 2007 over concerns related to adverse cardiovascular events. Since then, additional safety data has been generated, and following a resubmission and review by the Food and Drug Administration, in April 2019, tegaserod was once again approved for use in IBS-C under a more restricted labeling, confining use to women under 65 years of age without heart disease or additional cardiovascular risk factors. This review summarizes the regulatory journey of tegaserod and details the existing pharmacokinetic, physiologic, clinical, and safety data of tegaserod generated over the last 2 decades. The discussion also examines the future of tegaserod in the treatment of these constipation disorders, as well as its potential role in other related disorders of brain-gut interaction.

Aspalathus linearis (Rooibos) and Agmatine May Act Synergistically to Beneficially Modulate Intestinal Tight Junction Integrity and Inflammatory Profile

In order to promote gastrointestinal health, significant increases in the prevalence of gastrointestinal disorders should be paralleled by similar surges in therapeutics research. Nutraceutical interventions may play a significant role in patient management. The current study aimed to determine the potential of Aspalathus linearis (rooibos) to prevent gastrointestinal dysregulation resulting from high-dose trace-amine (TA) exposure. Considering the substantial female bias in functional gastrointestinal disorders, and the suggested phytoestrogenicity of rooibos, the study design allowed for a comparison between the effects of an ethanol extract of green rooibos and 17β-estradiol (E2). High levels of ρ-tyramine (TYR) and agmatine (AGM), but not β-phenethylamine (PEA) or tryptamine (TRP), resulted in prostaglandin E2 (PGE2) hypersecretion, increased tight-junction protein (TJP; occludin and ZO-1) secretion and (dissimilarly) disrupted the TJP cellular distribution profile. Modulating benefits of rooibos and E2 were TA-specific. Rooibos pre-treatment generally reduced IL-8 secretion across all TA conditions and prevented PGE2 hypersecretion after exposure to both TYR and AGM, but was only able to normalise TJP levels and the distribution profile in AGM-exposed cells. In contrast, E2 pre-treatment prevented only TYR-associated PGE2 hypersecretion and TJP dysregulation. Together, the data suggest that the antioxidant and anti-inflammatory effects of rooibos, rather than phytoestrogenicity, affect benefits illustrated for rooibos.

AGA Clinical Practice Guideline on the Pharmacological Management of Irritable Bowel Syndrome With Constipation

BACKGROUND & AIMS

Irritable bowel syndrome (IBS) is a common disorder of gut-brain interaction associated with significant disease burden. This American Gastroenterological Association guideline is intended to support practitioners in decisions about the use of medications for the pharmacological management of IBS-C and is an update of a prior technical review and guideline.

METHODS

The Grading of Recommendations Assessment, Development and Evaluation framework was used to assess evidence and make recommendations. The technical review panel prioritized clinical questions and outcomes according to their importance for clinicians and patients and conducted an evidence review of the following agents: tenapanor, plecanatide, linaclotide, tegaserod, lubiprostone, polyethylene glycol laxatives, tricyclic antidepressants, selective serotonin reuptake inhibitors, and antispasmodics. The Guideline Panel reviewed the evidence and used the Evidence-to-Decision Framework to develop recommendations.

CONCLUSIONS

The panel agreed on 9 recommendations for the management of patients with IBS-C. The panel made a strong recommendation for linaclotide (high certainty) and conditional recommendations for tenapanor, plecanatide, tegaserod, and lubiprostone (moderate certainty), polyethylene glycol laxatives, tricyclic antidepressants, and antispasmodics (low certainty). The panel made a conditional recommendation against the use of selective serotonin reuptake inhibitors (low certainty).

Management of scleroderma gastrointestinal disease: Lights and shadows

Gastrointestinal symptoms affect the great majority of patients with systemic sclerosis. Management of these complications is often challenging as any region of the gastrointestinal tract may be involved, and significant heterogeneity exists in clinical presentation, kinetics, and outcomes. Here, we highlight new findings relevant to the management of systemic sclerosis-related gastrointestinal disease (lights) and consider areas that we have yet to elucidate (shadows).

Editorial: risky business. What do sufferers' perceptions of risk from interventions for irritable bowel syndrome really mean?

This article is linked to Goodoory et al papers. To view these articles, visit https://doi.org/10.1111/apt.16816 and https://doi.org/10.1111/apt.16917

Re-evaluation of the Cardiovascular Safety Profile of Tegaserod: A Review of the Clinical Data

BACKGROUND AND AIMS

Tegaserod is a 5-HT₄ receptor agonist approved for irritable bowel syndrome with constipation in women <65 years of age without a history of cardiovascular ischemic events. Safety data are presented from 2 external adjudications from the 2018 Gastrointestinal Drugs Advisory Committee meeting supporting tegaserod's reintroduction after its voluntary 2007 withdrawal. Withdrawal was based on an internal adjudication using pooled placebo-controlled tegaserod data to identify potential cardiovascular ischemic signals.

METHODS

An independent committee conducted an external adjudication to evaluate 24 possible cardiovascular ischemic events (tegaserod: n = 20; placebo: n = 4) identified internally. A second independent external adjudication further evaluated these events.

RESULTS

A total of 18,645 patients were included (tegaserod: n = 11,614; placebo: n = 7031). The first adjudication identified 14 (0.075%) events (tegaserod: n = 13 [0.11%]; placebo: n = 1 [0.014%]). All patients had ≥1 cardiovascular risk factor, and 11 had ≥2. The second adjudication identified 390 events, 24 (0.13%) were classified as probable new or worsening events (tegaserod: 18 [0.16%]; placebo: 6 [0.09%]). For tegaserod, 7 (0.06%) were coronary or cerebrovascular ischemic events compared with 1 (0.01%) for placebo (odds ratio, 4.24; 95% confidence interval, 0.52-34.74; P = .273). All tegaserod patients reporting cardiovascular events had ≥1 risk, including cardiovascular disease, hyperlipidemia, ≥55 years of age, hypertension, diabetes, obesity, and smoking. Women <65 years of age without a history of cardiovascular ischemic events and ≤1 cardiovascular risk factor receiving tegaserod experienced no major adverse cardiovascular event(s).

CONCLUSIONS

Two independent, external adjudications suggest that tegaserod is safe for women <65 years of age with irritable bowel syndrome with constipation, no history of cardiovascular ischemic events, and ≤1 cardiovascular risk factor.

Mechanisms of Action of Current Pharmacologic Options for the Treatment of Chronic Idiopathic Constipation and Irritable Bowel Syndrome With Constipation

Multiple therapeutic agents are currently available for the treatment of chronic idiopathic constipation and irritable bowel syndrome with constipation. A better understanding of the mechanism of action of each treatment provides important insights into expected responses and is key to optimizing treatment outcomes. Some constipation treatments, such as stimulant laxatives, may increase bowel movement frequency but are ineffective at relieving, and may even exacerbate, abdominal symptoms. On the contrary, prescription treatments, such as the guanylyl cyclase-C agonists, for example, may improve bowel symptoms and reduce visceral hypersensitivity. This review summarizes the mechanisms of action of commonly used over-the-counter and prescription therapies for chronic idiopathic constipation and irritable bowel syndrome with constipation, outlining how these mechanisms contribute to the efficacy and safety of each treatment option.

Pharmacokinetics of DA-6886, A New 5-HT4 Receptor Agonist, in Rats

DA-6886 is a novel serotonin (5-hydroxytrypamine [5-HT]) receptor 4 agonist for the potential treatment of constipation-predominant irritable bowel syndrome. The purpose of this study was to validate the quantitative assay of DA-6886 in rat plasma and to evaluate the pharmacokinetics and tissue distribution of DA-6886 in rats. The liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for the robust quantification of DA-6886 in rat plasma was successfully validated and applied to the pharmacokinetic studies in rats. The pharmacokinetic parameters of DA-6886 in rats were evaluated following single intravenous or oral administration at three dose levels (2, 10, and 20 mg/kg). DA-6886 exhibited a smaller dose-normalized area under the plasma concentration–time curve (AUC) values and faster clearances in the low-dose group than in the high-dose group following both intravenous and oral administration. The steady-state volume of distribution (V_ss) of DA-6886 was relatively large (4.91–7.84 L/kg), which was consistent with its high distribution to the liver, kidney, lung, and digestive tract, and was dose-independent. After oral administration, the extent of absolute bioavailability (F) tended to increase (18.9–55.0%) with an increasing dose. The slope of the log-transformed AUC and/or C_max values versus log dose was greater than unity and greater for oral administration (~1.9) than for intravenous administration (~1.1). Because the nonlinear pharmacokinetics of DA-6886 was more obviously observed after oral administration, it appears that the saturation of pre-systemic intestinal and/or hepatic first-pass extraction of DA-6886 at high doses occurred.

The Role of Serotonin Neurotransmission in Gastrointestinal Tract and Pharmacotherapy

5-Hydroxytryptamine (5-HT, serotonin) is a neurotransmitter in both the central nervous system and peripheral structures, acting also as a hormone in platelets. Although its concentration in the gut covers >90% of all organism resources, serotonin is mainly known as a neurotransmitter that takes part in the pathology of mental diseases. Serotonin modulates not only CNS neurons, but also pain transmission and platelet aggregation. In the periphery, 5-HT influences muscle motility in the gut, bronchi, uterus, and vessels directly and through neurons. Serotonin synthesis starts from hydroxylation of orally delivered tryptophan, followed by decarboxylation. Serotonin acts via numerous types of receptors and clinically plays a role in several neural, mental, and other chronic disorders, such as migraine, carcinoid syndrome, and some dysfunctions of the alimentary system. 5-HT acts as a paracrine hormone and growth factor. 5-HT receptors in both the brain and gut are targets for drugs modifying serotonin neurotransmission. The aim of the present article is to review the 5-HT receptors in the gastrointestinal (GI) tract to determine the role of serotonin in GI physiology and pathology, including known GI diseases and the role of serotonin in GI pharmacotherapy.

Evaluation of the Pharmacokinetics of Felcisetrag (TAK-954), a 5-HT4 Receptor Agonist, in the Presence and Absence of Itraconazole, a Potent CYP3A4 Inhibitor

The 5-hydroxytryptamine type-4 receptor agonist felcisetrag (TAK-954) is being investigated for improving gastrointestinal motility in postoperative gastrointestinal dysfunction. Polypharmacy often occurs in this setting, and as in vitro data indicate, felcisetrag is primarily metabolized by cytochrome P450 (CYP) 3A4, its CYP3A4-mediated drug-drug interaction potential requires consideration. This phase 1, fixed-sequence, open-label, crossover trial (ClinicalTrials.gov identifier NCT03173170) investigated the effect of itraconazole, a potent CYP3A4 inhibitor, on felcisetrag pharmacokinetics in healthy adults. Over 2 study periods (period 1, 6 days; period 2, 9 days), participants received a single felcisetrag 0.2-mg intravenous dose (day 1, period 1; and day 4, period 2), and once-daily oral itraconazole 200-mg doses (days 1-8, period 2). For felcisetrag alone, felcisetrag total systemic exposure was lower than with itraconazole coadministration. The geometric mean ratio for area under the plasma concentration-time curve from time 0 to infinity of felcisetrag plus itraconazole: felcisetrag alone was 1.49 (90% confidence interval, 1.39-1.60). Peak exposure was similar between regimens (geometric mean ratio, 1.06; 90% confidence interval, 0.96-1.18), and both treatments were well tolerated. These data suggest limited CYP3A4-mediated drug-drug interaction inhibition for felcisetrag.

Prucalopride for Treatment of Upper Gastrointestinal Symptoms in Children

BACKGROUND

Upper gastrointestinal (GI) symptoms are common in pediatrics, and few prokinetics for children exist. The goal of this study was to determine the efficacy of prucalopride for treatment of upper GI symptoms and feeding difficulties in children.

METHODS

This was a retrospective study of patients prescribed prucalopride for upper GI symptoms at a single tertiary care center from July 2019 to January 2021. Demographic data, the indication for prucalopride, comorbidities, and feeding data were recorded. The primary outcome was improvement in the primary upper GI symptom at first follow-up after prucalopride initiation. Univariable and multivariable analyses were used to assess for factors associated with improvement.

RESULTS

The final study population included 71 patients who received prucalopride for treatment of upper GI symptoms. The most common indications were nausea (44%), feeding difficulties (20%), and reflux (11%). Patients had a median age of 16.7 years (range 1.9-21.8 years), and they had received 4 ± 4.8 years of care in our GI clinic and trialed 3.0 ± 2.0 other GI medications by the time of the prucalopride prescription. At follow-up 3.6 ± 2.9 months after the prucalopride was prescribed, 46 patients (65%) had symptomatic improvement of the upper GI symptom. Improvement was more likely in patients with enteral tubes (p = 0.04), pulmonary comorbidities (p = 0.006), and neurologic comorbidities (p = 0.02). Amongst patients with feeding difficulties, 79% of patients showed improvements in oral or tube feeding.

CONCLUSIONS

In this sample of children treated for refractory upper GI symptoms at a single tertiary care center, patients showed improvements in symptoms like nausea, reflux, and feeding difficulties after starting prucalopride.

Refractory Gastroesophageal Reflux Disease: A Management Update

Gastroesophageal reflux disease (GERD) is one of the most frequent gastrointestinal disorders. Proton pump inhibitors (PPIs) are effective in healing lesions and improving symptoms in most cases, although up to 40% of GERD patients do not respond adequately to PPI therapy. Refractory GERD (rGERD) is one of the most challenging problems, given its impact on the quality of life and consumption of health care resources. The definition of rGERD is a controversial topic as it has not been unequivocally established. Indeed, some patients unresponsive to PPIs who experience symptoms potentially related to GERD may not have GERD; in this case the definition could be replaced with “reflux-like PPI-refractory symptoms.” Patients with persistent reflux-like symptoms should undergo a diagnostic workup aimed at finding objective evidence of GERD through endoscopic and pH-impedance investigations. The management strategies regarding rGERD, apart from a careful check of patient's compliance with PPIs, a possible change in the timing of their administration and the choice of a PPI with a different metabolic pathway, include other pharmacologic treatments. These include histamine-2 receptor antagonists (H2RAs), alginates, antacids and mucosal protective agents, potassium competitive acid blockers (PCABs), prokinetics, gamma aminobutyric acid-B (GABA-B) receptor agonists and metabotropic glutamate receptor-5 (mGluR5) antagonists, and pain modulators. If there is no benefit from medical therapy, but there is objective evidence of GERD, invasive antireflux options should be evaluated after having carefully explained the risks and benefits to the patient. The most widely performed invasive antireflux option remains laparoscopic antireflux surgery (LARS), even if other, less invasive, interventions have been suggested in the last few decades, including endoscopic transoral incisionless fundoplication (TIF), magnetic sphincter augmentation (LINX) or radiofrequency therapy (Stretta). Due to the different mechanisms underlying rGERD, the most effective strategy can vary, and it should be tailored to each patient. The aim of this paper is to review the different management options available to successfully deal with rGERD.

Agent Clustering Strategy Based on Metabolic Flux Distribution and Transcriptome Expression for Novel Drug Development

The network module-based method has been used for drug repositioning. The traditional drug repositioning method only uses the gene characteristics of the drug but ignores the drug-triggered metabolic changes. The metabolic network systematically characterizes the connection between genes, proteins, and metabolic reactions. The differential metabolic flux distribution, as drug metabolism characteristics, was employed to cluster the agents with similar MoAs (mechanism of action). In this study, agents with the same pharmacology were clustered into one group, and a total of 1309 agents from the CMap database were clustered into 98 groups based on differential metabolic flux distribution. Transcription factor (TF) enrichment analysis revealed the agents in the same group (such as group 7 and group 26) were confirmed to have similar MoAs. Through this agent clustering strategy, the candidate drugs which can inhibit (Japanese encephalitis virus) JEV infection were identified. This study provides new insights into drug repositioning and their MoAs.

Safety/Efficacy of Prucalopride in Korean Patients with Chronic Constipation: Post-marketing Surveillance

Background/Aims

Constipation is a common gastrointestinal disorder. Prucalopride is a dihydrobenzofurancarboxamide derivative with gastrointestinal prokinetic activities and is recommended as an appropriate choice in patients unresponsive to laxatives. This study assessed the safety and efficacy of prucalopride in Korean patients with chronic constipation, in whom laxatives were ineffective.

Methods

This prospective, non-interventional post-marketing surveillance of prucalopride was conducted from 2012 to 2018 at 28 hospitals in Korea. Adults who received prucalopride for the symptomatic treatment of chronic constipation were included. The patients received 2 mg of prucalopride once daily or 1 mg once daily in patients older than 65 years. The baseline characteristics, adverse events (AEs), and seven-point scale of Clinical Global Impression-Improvement were collected.

Results

Of 601 patients, 67.7% were female, and the mean age was 62.3 years. Three hundred patients (49.9%) were older than 65 years. At the baseline, 70.0% of patients reported less than two instances of spontaneous complete bowel movements per week. AEs were reported in 107 patients (17.7%), including headache (3.2%) and diarrhea (2.8%). Seven serious AEs (SAEs) were reported in five patients (0.8%). The SAEs were resolved without complications; there were no cases of death. All SAEs were assessed as 'unlikely' causality with prucalopride. In 72.7% of patients, chronic constipation was improved by the prucalopride treatment during the study period.

Conclusions

This study demonstrated the promising safety and efficacy profile of prucalopride in clinical practice. Thus, prucalopride should be considered in patients with chronic constipation when bowel symptoms are refractory to simple laxatives.

Active Targeted Nanoemulsions for Repurposing of Tegaserod in Alzheimer's Disease Treatment

Background and Purpose: The activation of 5-HT₄ receptors with agonists has emerged as a valuable therapeutic strategy to treat Alzheimer’s disease (AD) by enhancing the nonamyloidogenic pathway. Here, the potential therapeutic effects of tegaserod, an effective agent for irritable bowel syndrome, were assessed for AD treatment. To envisage its efficient repurposing, tegaserod-loaded nanoemulsions were developed and functionalized by a blood–brain barrier shuttle peptide. Results: The butyrylcholinesterase inhibitory activity of tegaserod and its neuroprotective cellular effects were highlighted, confirming the interest of this pleiotropic drug for AD treatment. In regard to its drugability profile, and in order to limit its peripheral distribution after IV administration, its encapsulation into monodisperse lipid nanoemulsions (Tg-NEs) of about 50 nm, and with neutral zeta potential characteristics, was performed. The stability of the formulation in stock conditions at 4 °C and in blood biomimetic medium was established. The adsorption on Tg-NEs of peptide-22 was realized. The functionalized NEs were characterized by chromatographic methods (SEC and C₁₈/HPLC) and isothermal titration calorimetry, attesting the efficiency of the adsorption. From in vitro assays, these nanocarriers appeared suitable for enabling tegaserod controlled release without hemolytic properties. Conclusion: The developed peptide-22 functionalized Tg-NEs appear as a valuable tool to allow exploration of the repurposed tegaserod in AD treatment in further preclinical studies.

Tryptophan-derived serotonin-kynurenine balance in immune activation and intestinal inflammation

Endogenous tryptophan metabolism pathways lead to the production of serotonin (5‐hydroxytryptamine; 5‐HT), kynurenine, and several downstream metabolites which are involved in a multitude of immunological functions in both health and disease states. Ingested tryptophan is largely shunted to the kynurenine pathway (95%) while only minor portions (1%–2%) are sequestered for 5‐HT production. Though often associated with the functioning of the central nervous system, significant production of 5‐HT, kynurenine and their downstream metabolites takes place within the gut. Accumulating evidence suggests that these metabolites have essential roles in regulating immune cell function, intestinal inflammation, as well as in altering the production and suppression of inflammatory cytokines. In addition, both 5‐HT and kynurenine have a considerable influence on gut microbiota suggesting that these metabolites impact host physiology both directly and indirectly via compositional changes. It is also now evident that complex interactions exist between the two pathways to maintain gut homeostasis. Alterations in 5‐HT and kynurenine are implicated in the pathogenesis of many gastrointestinal dysfunctions, including inflammatory bowel disease. Thus, these pathways present numerous potential therapeutic targets, manipulation of which may aid those suffering from gastrointestinal disorders. This review aims to update both the role of 5‐HT and kynurenine in immune regulation and intestinal inflammation, and analyze the current knowledge of the relationship and interactions between 5‐HT and kynurenine pathways.

United European Gastroenterology (UEG) and European Society for Neurogastroenterology and Motility (ESNM) consensus on functional dyspepsia

BACKGROUND

Functional dyspepsia (FD) is one of the most common conditions in clinical practice. In spite of its prevalence, FD is associated with major uncertainties in terms of its definition, underlying pathophysiology, diagnosis, treatment, and prognosis.

METHODS

A Delphi consensus was initiated with 41 experts from 22 European countries who conducted a literature summary and voting process on 87 statements. Quality of evidence was evaluated using the grading of recommendations, assessment, development, and evaluation (GRADE) criteria. Consensus (defined as >80% agreement) was reached for 36 statements.

RESULTS

The panel agreed with the definition in terms of its cardinal symptoms (early satiation, postprandial fullness, epigastric pain, and epigastric burning), its subdivision into epigastric pain syndrome and postprandial distress syndrome, and the presence of accessory symptoms (upper abdominal bloating, nausea, belching), and overlapping conditions. Also, well accepted are the female predominance of FD, its impact on quality of life and health costs, and acute gastrointestinal infections, and anxiety as risk factors. In terms of pathophysiological mechanisms, the consensus supports a role for impaired gastric accommodation, delayed gastric emptying, hypersensitivity to gastric distention, Helicobacter pylori infection, and altered central processing of signals from the gastroduodenal region. There is consensus that endoscopy is mandatory for establishing a firm diagnosis of FD, but that in primary care, patients without alarm symptoms or risk factors can be managed without endoscopy. There is consensus that H. pylori status should be determined in every patient with dyspeptic symptoms and H. pylori positive patients should receive eradication therapy. Also, proton pump inhibitor therapy is considered an effective therapy for FD, but no other treatment approach reached a consensus. The long-term prognosis and life expectancy are favorable.

CONCLUSIONS AND INFERENCES

A multinational group of European experts summarized the current state of consensus on the definition, diagnosis and management of FD.

New Developments in Prokinetic Therapy for Gastric Motility Disorders

Prokinetic agents amplify and coordinate the gastrointestinal muscular contractions to facilitate the transit of intra-luminal content. Following the institution of dietary recommendations, prokinetics are the first medications whose goal is to improve gastric emptying and relieve symptoms of gastroparesis. The recommended use of metoclopramide, the only currently approved medication for gastroparesis in the United States, is for a duration of less than 3 months, due to the risk of reversible or irreversible extrapyramidal tremors. Domperidone, a dopamine D2 receptor antagonist, is available for prescription through the FDA's program for Expanded Access to Investigational Drugs. Macrolides are used off label and are associated with tachyphylaxis and variable duration of efficacy. Aprepitant relieves some symptoms of gastroparesis. There are newer agents in the pipeline targeting diverse gastric (fundic, antral and pyloric) motor functions, including novel serotonergic 5-HT4 agonists, dopaminergic D2/3 antagonists, neurokinin NK1 antagonists, and ghrelin agonist. Novel targets with potential to improve gastric motor functions include the pylorus, macrophage/inflammatory function, oxidative stress, and neurogenesis. In the current review, we discuss the use of pharmacological approaches with potential to enhance motor functions in the management of gastroparesis.

Gastrointestinal manifestations of systemic sclerosis: An updated review

Systemic sclerosis is an autoimmune disease characterized by vascular disease, fibrosis of the skin, and internal organ dysfunction. Gastrointestinal involvement is the most frequent complication of internal organs, impacting up to 90% of patients. Gastrointestinal involvement can affect any region of the gastrointestinal tract from the mouth to the anus, with a predominance of disorders being observed at the level of the upper digestive tract. The gastrointestinal involvement primarily involves the esophagus, small bowel, and rectum. The severity of gastrointestinal involvement affects quality of life and is a marker of worse prognosis and mortality in these patients. In this review, we describe the current findings regarding gastrointestinal involvement by this entity.

United European Gastroenterology (UEG) and European Society for Neurogastroenterology and Motility (ESNM) consensus on gastroparesis

BACKGROUND

Gastroparesis is a condition characterized by epigastric symptoms and delayed gastric emptying (GE) rate in the absence of any mechanical obstruction. The condition is challenging in clinical practice by the lack of guidance concerning diagnosis and management of gastroparesis.

METHODS

A Delphi consensus was undertaken by 40 experts from 19 European countries who conducted a literature summary and voting process on 89 statements. Quality of evidence was evaluated using grading of recommendations assessment, development, and evaluation criteria. Consensus (defined as ≥80% agreement) was reached for 25 statements.

RESULTS

The European consensus defined gastroparesis as the presence of symptoms associated with delayed GE in the absence of mechanical obstruction. Nausea and vomiting were identified as cardinal symptoms, with often coexisting postprandial distress syndrome symptoms of dyspepsia. The true epidemiology of gastroparesis is not known in detail, but diabetes, gastric surgery, certain neurological and connective tissue diseases, and the use of certain drugs recognized as risk factors. While the panel agreed that severely impaired gastric motor function is present in these patients, there was no consensus on underlying pathophysiology. The panel agreed that an upper endoscopy and a GE test are required for diagnosis. Only dietary therapy, dopamine-2 antagonists and 5-HT₄ receptor agonists were considered appropriate therapies, in addition to nutritional support in case of severe weight loss. No consensus was reached on the use of proton pump inhibitors, other classes of antiemetics or prokinetics, neuromodulators, complimentary, psychological, or more invasive therapies. Finally, there was consensus that gastroparesis adversely impacts on quality of life and healthcare costs and that the long-term prognosis of gastroparesis depends on the cause.

CONCLUSIONS AND INFERENCES

A multinational group of European experts summarized the current state of consensus on definition, symptom characteristics, pathophysiology, diagnosis, and management of gastroparesis.

A population pharmacokinetic-pharmacodynamic model of YH12852, a highly selective 5-hydroxytryptamine 4 receptor agonist, in healthy subjects and patients with functional constipation

YH12852, a novel, highly selective 5-hydroxytryptamine 4 (5-HT4 ) receptor agonist, is currently under development to treat patients with functional constipation. In this study, we aimed to develop a pharmacokinetic (PK)-pharmacodynamic (PD) model that adequately described the time courses of the plasma concentrations of YH12852 and its prokinetic effect as assessed by the Gastric Emptying Breath Test (GEBT) and to predict the prokinetic effect of YH12852 at higher doses through PD simulation. We used the plasma concentrations of YH12852 from patients with functional constipation and healthy subjects and the GEBT results from healthy subjects obtained from a phase I/IIa trial. The PK-PD modeling and covariate analysis were performed using NONMEM software. The prokinetic effect of YH12852 was described using a semimechanistic multicompartment PD model and an empirical model by Ghoos et al. A two-compartment model with first-order absorption adequately described the observed concentration-time profiles of YH12852. The semimechanistic multicompartment PD model and the revised Ghoos model with two slope parameters adequately described the observed kPCDt (the percent dose of 13 C excreted in the exhaled air at minute t after completing the test meal, multiplied by 1000) values. YH12852 accelerated gastric emptying even at low doses of 0.05-0.1 mg, and its prokinetic effect was greater in subjects suffering from more severe functional constipation. The PD simulation experiments revealed that the change from baseline in the half time for gastric emptying induced by YH12852 increased in a dose-dependent manner at 0.05-5 mg although the results at doses >0.1 mg were extrapolated. We also showed that the empirical Ghoos model is a special case of the general semimechanistic multicompartment PD model for gastric emptying.

The effect of prucalopride on gastric sensorimotor function and satiation in healthy volunteers

BACKGROUND

Gastric motor function alterations have been implicated in the pathogenesis of functional dyspepsia with postprandial distress syndrome (PDS). Prucalopride, a 5-TH4 agonist, is known to stimulate gastrointestinal motility. We aimed to evaluate the effect of prucalopride on gastric sensorimotor function in healthy subjects (HV).

METHODS

Barostat and intragastric pressure (IGP) measurements were performed in 17 HV (59% females, age 29.4 ± 2.7 y) after treatment with placebo or prucalopride (2 mg) (single-blind cross-over). Isobaric stepwise distensions and gastric sensations were assessed to determine gastric compliance and sensitivity. Gastric accommodation (GA) with the barostat was quantified before and after ingestion of 200 ml of a nutrient drink (ND). GA measured by IGP was quantified as the drop of IGP from baseline during the intragastric infusion of ND until maximal satiation (60 ml/min).

KEY RESULTS

Prucalopride did not affect barostat assessed gastric compliance or sensitivity. No differences were observed in GA after prucalopride. During the barostat study, 10 min after the meal, 7 HVs reported significantly higher ratings for nausea after prucalopride (p < 0.001), and vomiting was induced in 4 of the HVs. A positive correlation was observed between the delta mean perception of nausea with the delta mean increase of intra-balloon volume before and after meal ingestion (r = 0.37, p = 0.03). During IGP measurements, no effect on nutrient tolerance was observed and increased cramp severity scores were observed which were associated with a significant increase of distal IGP (r = 0.78, p < 0.0001).

CONCLUSIONS & INFERENCES

Prucalopride does not enhances gastric accommodation but it might increase sensitivity to gastric distention. Furthermore, the increase in sensitivity seems to be related to an increase in nausea with distension. Clinicaltrials.gov: NCT04429802.

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.

Chronic constipation in adults: Contemporary perspectives and clinical challenges. 2: Conservative, behavioural, medical and surgical treatment

BACKGROUND

Chronic constipation is a prevalent disorder that affects quality of life of patients and consumes resources in healthcare systems worldwide. In clinical practice, it is still considered a challenge as clinicians frequently are unsure as to which treatments to use and when. Over a decade ago, a Neurogastroenterology and Motility journal supplement devoted to the investigation and management of constipation was published (Neurogastroenterol Motil 2009;21(Suppl 2):1). In October 2018, the 3rd London Masterclass, entitled "Contemporary management of constipation" was held. The faculty members of this symposium were invited to write two reviews to present a collective synthesis of talks presented and discussions held during this meeting. The first review addresses epidemiology, diagnosis, clinical associations, pathophysiology, and investigation.

PURPOSE

The present is the second of these reviews, providing contemporary perspectives and clinical challenges regarding behavioral, conservative, medical, and surgical treatments for patients presenting with constipation. It includes a management algorithm to guide clinical practice.

Functional Dyspepsia: Diagnostic and Therapeutic Approaches

Functional dyspepsia is a common functional gastrointestinal (GI) disorder of gastroduodenal origin, diagnosed clinically in the presence of prototypical symptoms of epigastric pain and meal-related symptoms, and without structural explanation. The most recent diagnostic criteria provide for two functional dyspepsia subtypes, epigastric pain syndrome (EPS) and post-prandial distress syndrome (PDS) based on the predominant symptom pattern. The evaluation of dyspepsia should keep laboratory, imaging, and invasive testing to a minimum, as extensive or repetitive investigations are of rather low diagnostic yield in the absence of localizing symptoms or alarm features. Factors with etiopathologic relationships to functional dyspepsia include micro-inflammation, GI infections, abnormalities of gastroduodenal motility, visceral hypersensitivity, disturbances along the brain-gut axis, and psychological factors; all of these causative mechanisms have potential to partially explain symptoms in some functional dyspepsia patients, thus providing a rationale for the efficacy of a diversity of therapeutic approaches to functional dyspepsia. Management of dyspepsia symptoms relies upon both pharmacologic treatments and non-pharmacologic approaches, including psychological and complementary interventions. The evidence in support of established functional dyspepsia therapies is reviewed, and forms the basis for an effective functional dyspepsia treatment strategy emphasizing the patient's current symptom severity, pattern, and impact on the function and quality of life of the individual.

Current Opinion on Prucalopride in Gastroparesis and Chronic Constipation Treatment: A Focus on Patient Selection and Safety

Prucalopride is a third-generation, highly selective 5-hydroxytryptamine 4 (5-HT4) receptor agonist. Many recent studies indicate prucalopride may play an important role in various motility disorders. The aim of this study was to investigate safety and patient selection considerations when using prucalopride as gastroparesis and chronic constipation treatment. We systematically searched PubMed, Embase, the Cochrane Central Register and ClinicalTrials.gov, and we reviewed all studies that evaluated prucalopride for the treatment of gastroparesis and chronic idiopathic constipation in adults. Prucalopride is an effective and safe option based on all the studies currently conducted. Thus, it may be the first-line treatment in the future. Prucalopride has the potential to be useful in the treatment of functional constipation and other forms of gastrointestinal diseases (eg, gastroparesis). Through the research on this potential, prucalopride is expected to be a useful and versatile option for treating gastrointestinal diseases in the future.

Management of Ineffective Esophageal Hypomotility

Esophageal hypomotility in general and especially ineffective esophageal motility according to the Chicago criteria of primary motility disorders of the esophagus, is one of the most frequently diagnosed motility disorders on high resolution manometry and results in a large number of patients visiting gastroenterologists. Most patients with esophageal hypomotility present with gastroesophageal reflux symptoms or dysphagia. The clinical relevance of the motility pattern, however, is not well established but seems to be correlated with disease severity in reflux patients. The correlation with dysphagia is less clear. Prokinetic agents are commonly prescribed as first line pharmacologic intervention to target esophageal smooth muscle contractility and improve esophageal motor functions. However, the beneficial effects of these medications are limited and only confined to some specific drugs. Serotonergic agents, including buspirone, mosapride and prucalopride have been shown to improve parameters of esophageal motility although the effect on symptoms is less clear. Understanding on the complex correlation between esophageal hypomotility and esophageal symptoms as well as the limited evidence of prokinetic agents is necessary for physicians to appropriately manage patients with Ineffective Esophageal Motility (IEM).

United European Gastroenterology (UEG) and European Society for Neurogastroenterology and Motility (ESNM) consensus on functional dyspepsia

Background

Functional dyspepsia (FD) is one of the most common conditions in clinical practice. In spite of its prevalence, FD is associated with major uncertainties in terms of its definition, underlying pathophysiology, diagnosis, treatment, and prognosis.

Methods

A Delphi consensus was initiated with 41 experts from 22 European countries who conducted a literature summary and voting process on 87 statements. Quality of evidence was evaluated using the grading of recommendations, assessment, development, and evaluation (GRADE) criteria. Consensus (defined as >80% agreement) was reached for 36 statements.

Results

The panel agreed with the definition in terms of its cardinal symptoms (early satiation, postprandial fullness, epigastric pain, and epigastric burning), its subdivision into epigastric pain syndrome and postprandial distress syndrome, and the presence of accessory symptoms (upper abdominal bloating, nausea, belching), and overlapping conditions. Also, well accepted are the female predominance of FD, its impact on quality of life and health costs, and acute gastrointestinal infections, and anxiety as risk factors. In terms of pathophysiological mechanisms, the consensus supports a role for impaired gastric accommodation, delayed gastric emptying, hypersensitivity to gastric distention, Helicobacter pylori infection, and altered central processing of signals from the gastroduodenal region. There is consensus that endoscopy is mandatory for establishing a firm diagnosis of FD, but that in primary care, patients without alarm symptoms or risk factors can be managed without endoscopy. There is consensus that H. pylori status should be determined in every patient with dyspeptic symptoms and H. pylori positive patients should receive eradication therapy. Also, proton pump inhibitor therapy is considered an effective therapy for FD, but no other treatment approach reached a consensus. The long‐term prognosis and life expectancy are favorable.

Conclusions and Inferences

A multinational group of European experts summarized the current state of consensus on the definition, diagnosis and management of FD.

Current knowledge

Functional dyspepsia is one of the most common conditions encountered in clinical practice.

There is a lack of guidance for clinicians in guiding diagnosis and treatment of this prevalent condition.

No treatments are currently approved for the treatment of functional dyspepsia in Europe.

What is new here

A Delphi panel consisting of 41 experts from 22 European countries established the level of consensus on 87 statements regarding functional dyspepsia.

The statements reaching consensus serve to guide clinicians in recognizing, diagnosing and treating FD in clinical practice.

Endoscopy is mandatory for establishing a firm diagnosis of functional dyspepsia D, but in primary care patients without alarm symptoms or risk factors can be managed without endoscopy.

Helicobacter pylori status should be determined in every patient with dyspeptic symptoms and H. Pylori positive patients should receive eradication therapy.

Proton pump inhibitor‐therapy is considered an effective therapy for FD, but no other treatment approach reached consensus support.