The effect of cisapride on oesophageal motility and lower sphincter function in patients with gastro-oesophageal reflux disease

Review: The Role of Cannabinoids on Esophageal Function-What We Know Thus Far

The endocannabinoid system (ECS) primarily consists of cannabinoid receptors (CBRs), endogenous ligands, and enzymes for endocannabinoid biosynthesis and inactivation. Although the presence of CBRs, both CB1 and CB2, as well as a third receptor (G-protein receptor 55 [GPR55]), has been established in the gastrointestinal (GI) tract, few studies have focused on the role of cannabinoids on esophageal function. To date, studies have shown their effect on GI motility, inflammation and immunity, intestinal and gastric acid secretion, nociception and emesis pathways, and appetite control. Given the varying and sometimes limited efficacy of current medical therapies for diseases of the esophagus, further understanding and investigation into the interplay of the ECS on esophageal health and disease may present new therapeutic modalities that may help advance current treatment options. In this brief review, the current understanding of the ECS role in various esophageal functions and disorders is presented.

High-resolution manometric evaluation of the effects of cisapride on the esophagus during administration of solid and liquid boluses in awake healthy dogs

OBJECTIVE To validate the use of high-resolution manometry (HRM) in awake, healthy dogs and compare the effects of bolus type (liquid vs solid) and drug treatment (saline [0.9% NaCl] solution [SS] vs cisapride) on esophageal pressure profiles. ANIMALS 8 healthy dogs. PROCEDURES In a crossover study, each dog received SS (10 mL) IV, and HRM was performed during oral administration of 10 boluses (5 mL each) of water or 10 boluses (5 g each) of canned food. Cisapride (1 mg/kg in 60 mL of SS) was subsequently administered IV to 7 dogs; HRM and bolus administration procedures were repeated. Two to 4 weeks later, HRM was repeated following administration of SS and water and food boluses in 4 dogs. Pressure profile data were obtained for all swallows, and 11 outcome variables were statistically analyzed. RESULTS After SS administration, predicted means for the esophageal contractile integral were 850.4 cm/mm Hg/s for food boluses and 660.3 cm/mm Hg/s for water boluses. Predicted means for esophageal contraction front velocity were 6.2 cm/s for water boluses and 5.6 cm/s for food boluses after SS administration. Predicted means for residual LES pressure were significantly higher following cisapride administration. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that HRM was feasible and repeatable in awake healthy dogs of various breeds and sizes. Stronger esophageal contractions and faster esophageal contraction velocity occurred during solid bolus and liquid bolus swallows, respectively. Lower esophageal sphincter pressure increased significantly following cisapride administration. Esophageal contractions and bolus transit latency should be further evaluated by HRM in clinically dysphagic dogs.

Effects of prucalopride on esophageal secondary peristalsis in humans

Objectives:

Prucalopride, a high-affinity 5-hydroxytrypatamine 4 (5-HT₄) receptors agonist, has been shown to improve colon motility in adults. Secondary peristalsis helps the clearance of retained food bolus and refluxate from the esophagus, but the effects of prucalopride on esophageal secondary peristalsis are unknown. We aimed to assess the effects of prucalopride on distension-induced secondary peristalsis in healthy adults.

Methods:

Two separate sessions with prucalopride and placebo were performed in 11 healthy adults to test the effects on secondary peristalsis. Secondary peristalsis was performed with slow and rapid mid-esophageal injections of air after a baseline recording of esophageal motility.

Results:

Prucalopride significantly decreased the threshold volume to generate secondary peristalsis during slow air injection (9.8±1.4 vs. 14.4±0.9 ml, P=0.005) and rapid air injection (3.9±0.3 vs. 5.2±0.4 ml, P=0.008). Secondary peristalsis was generated more frequently after application of prucalopride (80% (70–100%) vs. 70% (60–73%), P=0.01). Prucalopride increased the wave amplitude of distal esophagus during slow air injection (147.9±28.5 vs. 104.2±16.8 mm Hg, P=0.048) and rapid air injection (128.0±13.3 vs. 105.7±12.3 mm Hg, P=0.016). Primary peristaltic amplitudes were also significantly increased by the application of prucalopride.

Conclusions:

Acute administration of prucalopride enhances mechanosensitivity of distension-induced secondary peristalsis and promotes esophageal contractility in healthy adults. Whether prucalopride could be a therapeutic option for the treatment of subjects with esophageal hypomotility needs further study.

Regionally dependent neuromuscular functions of motilin and 5-HT₄ receptors in human isolated esophageal body and gastric fundus

BACKGROUND

Motilin agonists promote human gastric motility and cholinergic activity, but excitatory and inhibitory actions are reported in the esophagus. The effect of 5-HT₄ agonists in esophagus is also unclear. Perhaps the use of drugs with additional actions explains the variation. The aim, therefore, was to examine how motilin and prucalopride, selective motilin and 5-HT₄ receptor agonists, modulate neuromuscular functions in human esophagus and gastric fundus.

METHODS

Electrical field stimulation (EFS) evoked nerve-mediated contractions of circular and longitudinal muscle from human esophageal body and circular muscle from gastric fundus.

KEY RESULTS

In esophageal circular muscle EFS evoked brief contraction, followed by another contraction on termination of EFS, each prevented by atropine. Nitric oxide synthase inhibition facilitated contraction during EFS and the overall contraction became monophasic. In esophagus longitudinal muscle and gastric fundus, EFS evoked cholinergically mediated, monophasic contractions, attenuated by simultaneous nitrergic activation. Motilin (100-300 nM) reduced esophagus circular muscle contractions during EFS, unaffected by L-NAME or apamin. Motilin 300 nM also reduced EFS-evoked contractions of longitudinal muscle. Similar concentrations of motilin facilitated cholinergic activity in the fundus and increased baseline muscle tension. Prucalopride facilitated EFS-evoked contractions in esophagus (tested at 30 μM) and fundus (0.1-30 μM).

CONCLUSIONS & INFERENCES

Selective motilin and 5-HT₄ agonists have different, region-dependent abilities to modulate human esophageal and stomach neuromuscular activity, exemplified by weak inhibition (motilin) or excitation (5-HT₄) in esophageal body and excitation for both in stomach. In different patients with motility dysfunctions, motilin and 5-HT₄ agonists may reduce gastro-esophageal reflux in different ways.

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

BACKGROUND

The nonselective 5-HT(4) receptor agonists, cisapride and tegaserod have been associated with cardiovascular adverse events (AEs).

AIM

To perform a systematic review of the safety profile, particularly cardiovascular, of 5-HT(4) agonists developed for gastrointestinal disorders, and a nonsystematic summary of their pharmacology and clinical efficacy.

METHODS

Articles reporting data on cisapride, clebopride, prucalopride, mosapride, renzapride, tegaserod, TD-5108 (velusetrag) and ATI-7505 (naronapride) were identified through a systematic search of the Cochrane Library, Medline, Embase and Toxfile. Abstracts from UEGW 2006-2008 and DDW 2008-2010 were searched for these drug names, and pharmaceutical companies approached to provide unpublished data.

RESULTS

Retrieved articles on pharmacokinetics, human pharmacodynamics and clinical data with these 5-HT(4) agonists, are reviewed and summarised nonsystematically. Articles relating to cardiac safety and tolerability of these agents, including any relevant case reports, are reported systematically. Two nonselective 5-HT(4) agonists had reports of cardiovascular AEs: cisapride (QT prolongation) and tegaserod (ischaemia). Interactions with, respectively, the hERG cardiac potassium channel and 5-HT(1) receptor subtypes have been suggested to account for these effects. No cardiovascular safety concerns were reported for the newer, selective 5-HT(4) agonists prucalopride, velusetrag, naronapride, or for nonselective 5-HT(4) agonists with no hERG or 5-HT(1) affinity (renzapride, clebopride, mosapride).

CONCLUSIONS

5-HT(4) agonists for GI disorders differ in chemical structure and selectivity for 5-HT(4) receptors. Selectivity for 5-HT(4) over non-5-HT(4) receptors may influence the agent's safety and overall risk-benefit profile. Based on available evidence, highly selective 5-HT(4) agonists may offer improved safety to treat patients with impaired GI motility.

New pharmacologic approaches in gastroesophageal reflux disease

This article highlights current and emerging pharmacological treatments for gastroesophageal reflux disease (GERD), opportunities for improving medical treatment, the extent to which improvements may be achieved with current therapy, and where new therapies may be required. These issues are discussed in the context of current thinking on the pathogenesis of GERD and its various manifestations and on the pharmacologic basis of current treatments.

Effects of mosapride on esophageal secondary peristalsis in humans

BACKGROUND

Secondary peristalsis is important for the clearance of refluxate or retained food bolus from the esophagus. Mosapride is a prokinetic agent that enhances GI motility by stimulating 5-hydroxytrypatamine(4) (5-HT(4) ) receptors, but its effects on secondary peristalsis are yet unclear in humans. We aimed to investigate the effect of a 5-HT(4) agonist mosapride on esophageal distension-induced secondary peristalsis in normal subjects.

METHODS

After a baseline recording esophageal motility, secondary peristalsis was generated by slow and rapid mid-esophageal injections of air in 15 healthy subjects. Two separate sessions with 40mg oral mosapride or placebo were randomly performed to test their effects on esophageal secondary peristalsis.

KEY RESULTS

Mosapride decreased the threshold volume for triggering secondary peristalsis during rapid air distension (4.5±0.3 vs 5.3±0.4mL; P=0.04) but not slow air distension (14.3±1.2 vs 13.3±1.3mL; P=0.41). Secondary peristalsis was triggered more frequently in response to rapid air distension after application of mosapride [100% (90-100%) vs 90% (80-100%); P=0.02]. Mosapride significantly increased pressure wave amplitudes of secondary peristalsis during slow (135.4±13.8 vs 105.0±12.9mmHg; P=0.001) and rapid air distensions (124.0±11.6 vs 95.9±14.0mmHg; P=0.002).

CONCLUSIONS & INFERENCES

Mosapride enhances sensitivity to distension-induced secondary peristalsis and facilitates secondary peristaltic contractility. These data provide an evidence for modulation of esophageal secondary peristalsis by the 5-HT(4) agonist mosapride, as well support for its clinical utility.

Cisapride: what can we learn from the rise and fall of a prokinetic?

Cisapride, the prototype serotonergic agent, evolved from a body of research that defined the key roles of serotonergic receptors in gastrointestinal motor and sensory function. Impressed by its in vitro properties and encouraged by clinical trial data, cisapride became the drug of choice for the treatment of a wide range of motility disorders and clinicians appeared impressed by its efficacy and comfortable with its side-effect profile. Once serious cardiac events began to be reported in association with cisapride therapy, dark clouds rapidly gathered and soon enveloped the drug, leading to its widespread withdrawal from markets. What lessons can we learn from the story of cisapride? How can its brief but spectacular rise and equally sensational demise inform the development of new drugs which are so sorely needed in the management of motility and functional gastrointestinal disorders? This review explores the background to the development of cisapride, its history in clinical trials and the experience with adverse events and, in so doing, attempts to identify lessons for the future in the therapeutics of enteric neuromodulatory drugs.

WITHDRAWN: Medical treatments in the short term management of reflux oesophagitis

BACKGROUND

Oesophagitis arises when reflux of acid from the stomach into the oesophagus causes mucosal inflammation. It is a common problem and a systematic review on the optimum treatment would be useful.

OBJECTIVES

To assess the effectiveness of proton pump inhibitors (PPIs), H2 receptor antagonists (H2RAs), prokinetic therapy, sucralfate and placebo in healing oesophagitis or curing reflux symptoms or both. To compare adverse effects with the different treatments.

SEARCH STRATEGY

We searched MEDLINE, EMBASE, CINAHL, Cochrane Central Register of Controlled Trials and the National Research Register until December 2004 and reference lists of articles. We also contacted manufacturers and researchers in the field.

SELECTION CRITERIA

Randomised controlled trials assessing the healing of oesophagitis or reflux symptoms or both. Treatment involving PPIs, H2RAs, prokinetics, sucralfate and combinations either in comparison to another treatment regimen or to placebo for 2 and 12 weeks.

DATA COLLECTION AND ANALYSIS

Two reviews independently assessed trial quality and extracted data.

MAIN RESULTS

We included 134 trials involving 35,978 oesophagitis participants. Five RCTs evaluated standard dose of PPI versus placebo in 965 participants. There was a statistically significant benefit of taking standard dose PPI therapy compared to placebo in healing of oesophagitis (RR = 0.22; 95% CI 0.15 to 0.31). Ten RCTs reported on the outcome for H2RA versus placebo evaluating 1241 participants. There was statistically significant benefit of taking H2RA compared to placebo in healing of oesophagitis (RR 0.74,95% CI = 0.66 to 0.84). Three RCTs evaluated prokinetic therapy versus placebo in 198 participants. There was no statistically significant benefit of taking prokinetic therapy compared to placebo in healing of oesophagitis (RR 0.71, 95% CI 0.46 to 1.10). Twenty six RCTs reported the outcome for PPI versus H2RA or H2RA plus prokinetics, evaluating 4032 participants. There was statistically significant benefit of taking PPI therapy compared to H2RA or H2RA plus prokinetics in healing of oesophagitis (RR 0.51, 95% CI 0.44 to 0.59).

AUTHORS' CONCLUSIONS

PPI therapy is the most effective therapy in oesophagitis but H2RA therapy is also superior to placebo. There is a paucity of evidence on prokinetic therapy but no evidence that it is superior to placebo.

New pharmacologic approaches in gastroesophageal reflux disease

This article highlights current and emerging pharmacological treatments for gastroesophageal reflux disease (GERD), opportunities for improving medical treatment, the extent to which improvements may be achieved with current therapy, and where new therapies may be required. These issues are discussed in the context of current thinking on the pathogenesis of GERD and its various manifestations and on the pharmacologic basis of current treatments.

Advances in roles of prokinetic agents in the treatment of gastroesophageal reflux disease

Gastroesophageal reflux disease (GERD) is characterized by the reflux of gastric content into esophagus with or without histological changes. Pathogenesis of GERD is lower esophageal sphincter (LES) dysfunction, abnormal clearing capacity of refluxed materials, delayed gastric emptying and abnormal resistance of esophageal mucosa to gastric acid, but the primary upper gastrointestinal motility dysfunction is regarded as the most important factor in general. Therefore, prokinetic agents which can restore gastric motility with increasing of LES and esophageal motility have been developed and used frequently in the treatment of GERD. There are several prokinetic agents such as metoclopramide, domperidone, cisapride and mosapride that facilitate acetylcholine release from the enteric cholinergic neurons through a selective 5-HT₄ receptor agonistic action. It is considered that prokinetic agents have the same effect as H2 blocker in the treatment of patients with mild GERD. Additionally, it was reported that a combination therapy with prokinetic agents and proton pump inhibitors (PPI) or H2 receptor antagonists (H2RAs) is more effective than monotherapy in patients with severe GERD. This article reviews the recent advances in the role of prokinetic agents in the treatment of gastroesophageal reflux disease.

Prokinetic drug utility in the treatment of gastroesophageal reflux esophagitis: a systematic review of randomized controlled trials

BACKGROUND

Esophagitis caused by gastroesophageal reflux disease (GERD) results in appreciable morbidity and economic burden. No systematic review has addressed the effectiveness of prokinetic drugs in the treatment of GERD esophagitis in adults.

OBJECTIVE

To determine the utility of prokinetic drugs in improving symptoms and endoscopic lesions in patients with GERD esophagitis.

METHODS

We included randomized controlled trials that compared prokinetic drugs with placebo. A systematic search included the Cochrane Controlled Trial Register, MEDLINE, CINAHL, LILACS, EMBASE, a manual search of books and article references, and contact with pharmaceutical companies. Reviewers assessed methodological quality and extracted data that were combined using a random effects model.

RESULTS

Eighteen articles met the eligibility criteria; of these, 13 used prokinetic drugs alone, 4 tested prokinetic drugs as additional therapy in patients receiving histamine-2 receptor blockers, and 1 tested them in patients receiving proton pump inhibitors. Seven studies evaluated clinical improvement only, 5 addressed endoscopic improvement only, and 6 reported both outcomes. Four studies failed to provide adequate data for pooling; 3 of the 4 reported results that suggested symptomatic benefit with prokinetic agents. Nine studies (379 patients) that provided the required data suggested a higher incidence of clinical improvement with prokinetic drugs versus placebo (relative risk [RR] 1.70, 95% confidence interval [CI] 1.37-2.12, heterogeneity p = 0.47, I(2) = 0%). Clinical improvement occurred in 53 out of 175 patients (30%) of the control group; applying the relative risk of 1.70 and associated confidence interval suggests that absolute increases in patients improved might vary from 18% to 41% (number needed to treat approximately 3 to 6). Improvement was similar in 4 studies in which the prokinetic agent was added to an antisecretory drug. The funnel plot, however, suggests the possibility of publication bias. Eleven studies (887 patients) suggested a higher likelihood of endoscopic improvement or healing esophagitis with prokinetic drugs (RR 1.26, 95% CI 1.03-1.53) but with significant heterogeneity (heterogeneity p = .05, I(2) = 46.2%) that we couldn't explain with an a priori hypothesis. When we evaluated endoscopic healing as the main outcome we observed a trend toward better results in the treatment group, also with inexplicable heterogeneity (RR 1.36, CI 95% 0.97-1.89, I(2) = 61%).

CONCLUSIONS

Randomized controlled trials provide moderate-quality evidence that prokinetic drugs improve symptoms in patients with reflux esophagitis and low-quality evidence that they have an impact on endoscopic healing.

Medical treatments in the short term management of reflux oesophagitis

BACKGROUND

Oesophagitis arises when reflux of acid from the stomach into the oesophagus causes mucosal inflammation. It is a common problem and a systematic review on the optimum treatment would be useful.

OBJECTIVES

To assess the effectiveness of proton pump inhibitors (PPIs), H2 receptor antagonists (H2RAs), prokinetic therapy, sucralfate and placebo in healing oesophagitis or curing reflux symptoms or both. To compare adverse effects with the different treatments.

SEARCH STRATEGY

We searched MEDLINE, EMBASE, CINAHL, Cochrane Central Register of Controlled Trials and the National Research Register until December 2004 and reference lists of articles. We also contacted manufacturers and researchers in the field.

SELECTION CRITERIA

Randomised controlled trials assessing the healing of oesophagitis or reflux symptoms or both. Treatment involving PPIs, H2RAs, prokinetics, sucralfate and combinations either in comparison to another treatment regimen or to placebo for 2 and 12 weeks.

DATA COLLECTION AND ANALYSIS

Two reviews independently assessed trial quality and extracted data.

MAIN RESULTS

We included 134 trials involving 35,978 oesophagitis participants. Five RCTs evaluated standard dose of PPI versus placebo in 965 participants. There was a statistically significant benefit of taking standard dose PPI therapy compared to placebo in healing of oesophagitis (RR = 0.22; 95% CI 0.15 to 0.31). Ten RCTs reported on the outcome for H2RA versus placebo evaluating 1241 participants. There was statistically significant benefit of taking H2RA compared to placebo in healing of oesophagitis (RR 0.74,95% CI = 0.66 to 0.84). Three RCTs evaluated prokinetic therapy versus placebo in 198 participants. There was no statistically significant benefit of taking prokinetic therapy compared to placebo in healing of oesophagitis (RR 0.71, 95% CI 0.46 to 1.10). Twenty six RCTs reported the outcome for PPI versus H2RA or H2RA plus prokinetics, evaluating 4032 participants. There was statistically significant benefit of taking PPI therapy compared to H2RA or H2RA plus prokinetics in healing of oesophagitis (RR 0.51, 95% CI 0.44 to 0.59).

AUTHORS' CONCLUSIONS

PPI therapy is the most effective therapy in oesophagitis but H2RA therapy is also superior to placebo. There is a paucity of evidence on prokinetic therapy but no evidence that it is superior to placebo.

The serotonin signaling system: from basic understanding to drug development for functional GI disorders

Serotonin is an important gastrointestinal signaling molecule. It is a paracrine messenger utilized by enterochromaffin (EC) cells, which function as sensory transducers. Serotonin activates intrinsic and extrinsic primary afferent neurons to, respectively, initiate peristaltic and secretory reflexes and to transmit information to the central nervous system. Serotonin is also a neurotransmitter utilized by a system of long descending myenteric interneurons. Serotonin is synthesized through the actions of 2 different tryptophan hydroxylases, TpH1 and TpH2, which are found, respectively, in EC cells and neurons. Serotonin is inactivated by the serotonin reuptake transporter (SERT)-mediated uptake into enterocytes or neurons. The presence of many serotonin receptor subtypes enables selective drugs to be designed to therapeutically modulate gastrointestinal motility, secretion, and sensation. Current examples include tegaserod, a 5-HT(4) partial agonist, which has been approved for treatment of irritable bowel syndrome (IBS) with constipation in women and for chronic constipation in men and women. The 5-HT(3) antagonists, granisetron and ondansetron, are useful in combating the nausea associated with cancer chemotherapy, and alosetron is employed in the treatment of IBS with diarrhea. Serotonergic signaling abnormalities have also been putatively implicated in the pathogenesis of functional bowel diseases. Other compounds, for which efficacy has not been rigorously established, but which may have value, include tricyclic antidepressants and serotonin selective reuptake inhibitors to combat IBS, and 5-HT(1) agonists, which enhance gastric accommodation, to treat functional dyspepsia. The initial success encountered with serotonergic agents holds promise for newer and more potent insights and therapies of brain-gut disorders.

The effect of mosapride on esophageal motility and bolus transit in asymptomatic volunteers

GOALS

To evaluate the effect of mosapride, a selective 5-hydroxytryptamine-4 agonist, on esophageal motility and bolus transit in asymptomatic volunteers.

STUDY

Twenty healthy subjects participated in two experiments, 7 days apart, and we utilized a randomized, double-blind cross-over design with 3-day pretreatments of placebo or mosapride. All subjects underwent combined intraluminal impedance manometry.

RESULTS

There was no difference in the amplitude, the duration, and the esophageal peristaltic patterns between the two pretreatments. The lower esophageal sphincter (LES) pressure and the number of transient LES relaxations did not change after mosapride vs. placebo. However, the rate of complete bolus transit in liquid swallows was higher with mosapride pretreatment (92.2%) than with placebo (84.6%; P < 0.01). The total bolus transit time in all liquid swallows showed a tendency to shorten after mosapride treatment (P = 0.06). The liquid bolus transit became faster after mosapride, especially in manometrically ineffective liquid swallows (P < 0.01). The total bolus transit time for manometrically normal viscous swallows decreased after pretreatment with mosapride (7.7 seconds; range, 6.8-9.2) in comparison with placebo (8.1 seconds; range, 7.1-11.1; P < 0.05).

CONCLUSIONS

Mosapride increases the rate of complete bolus transit in the esophagus, and enhances esophageal bolus transit in asymptomatic volunteers.

Pharmacological targets in gastro-oesophageal reflux disease

Although proton pump inhibitors have become the mainstay of treatment in gastro-oesophageal reflux disease (GORD), there are still unmet needs in the management of this very common disorder. For example, all current proton pump inhibitors have a relatively slow onset of action and their activity is limited mainly to the post-prandial period with far less effective inhibition of nocturnal acid secretion. In order to achieve more potent, rapid and sustained acid inhibition several compounds are currently under development, such as new proton pump inhibitors with a prolonged plasma half-life, potassium competitive ATPase blockers (PCABs), histamine H3 agonists, and gastrin antagonists. Acid suppression does not, however, cure the disease and relapses are frequently observed after discontinuation of proton pump inhibitor therapy. Among the different abnormalities involved in the pathophysiology of this multifactorial disease, transient lower oesophageal sphincter relaxations represent the major mechanism responsible for episodes of reflux. Baclofen, the prototype GABA(B) receptor agonist, is one of the most potent inhibitors of transient lower oesophageal sphincter relaxations identified. To date the transfer of these relaxation-controlling pharmacological agents into clinical practice has however been hampered by the occurrence of unacceptable side effects. Beside "anti-relaxation therapy", the potential of novel prokinetics such as motilin agonists has been explored, especially since the motilin receptor has been cloned. Thus far the broad therapeutic value of prokinetics in GORD does, however, seem very limited in terms of efficacy with respect to oesophageal motility and acid exposure. Lastly, further research is necessary to better understand the complex mechanisms involved in oesophageal sensitivity and mucosal defence.

Comparison of efficacy of pantoprazole alone versus pantoprazole plus mosapride in therapy of gastroesophageal reflux disease: a randomized trial

The present study aimed to compare the efficacy for the therapy of GERD of pantoprazole alone with a combination of pantoprazole and mosapride. The study was a prospective, randomized trial involving 68 patients suffering heartburn and/or regurgitation at least twice a week for 6 weeks. Sixty-one patients consented to be randomized to receive either pantoprazole 40 mg b.i.d. (n = 33, group A) or pantoprazole 40 mg b.i.d. plus mosapride 5 mg t.d.s. (n = 28, group B) for 8 weeks. Twenty-four-hour esophageal pH-metry and endoscopy were conducted at recruitment and endoscopy was repeated at 8 weeks in all the patients studied. There were no differences in symptomatic responses to therapy between the groups (69.7% vs 89.2%; P = 0.11). The mean symptom score after 8 weeks was significantly lower in group B (3.78 +/- 3.62 vs 1.67 +/- 2.09; P = 0.009). Nonerosive esophagitis was present in 29 patients. In patients with nonerosive GERD there was no significant difference in symptomatic response to either regimen (17/20 in group A and 7/9 in group B responded; P = 0.63). In erosive esophagitis, symptomatic responses occurred more frequently in group B, 18/19 (94.7%), than in group A, 6/13 (46.2%; P = 0.003). However endoscopic healing of esophagitis occurred equally with either regimen (6/11, 54.5% in group A; 12/17, 70.5% in group B; P = 0.44). In nonerosive GERD, the addition of mosapride offers no benefit over pantoprazole alone. A combination of pantoprazole and mosapride is more effective than pantoprazole alone in providing symptomatic relief to patients with erosive GERD.

Functions of 5-HT2A receptor and its antagonists in the cardiovascular system

The serotonin (5-hydroxytryptamine, 5-HT) receptors have conventionally been divided into seven subfamilies, most of which have several subtypes. Among them, 5-HT(2A) receptor is associated with the contraction of vascular smooth muscle, platelet aggregation and thrombus formation and coronary artery spasms. Accordingly, selective 5-HT(2A) antagonists may have potential in the treatment of cardiovascular diseases. Sarpogrelate, a selective 5-HT(2A) antagonist, has been introduced clinically as a therapeutic agent for the treatment of ischemic diseases associated with thrombosis. Molecular modeling studies also suggest that sarpogrelate is a 5-HT(2A) selective antagonist and is likely to have pharmacological effects beneficial in the treatment of cardiovascular diseases. This review describes the above findings as well as the signaling linkages of the 5-HT(2A) receptors and the mode of agonist binding to 5-HT(2A) receptor using data derived from molecular modeling and site-directed mutagenesis.

Progress with novel pharmacological strategies for gastro-oesophageal reflux disease

Gastro-oesophageal reflux disease (GORD) is a chronic disorder characterised by an increased exposure of the oesophagus to intragastric contents. Currently, GORD symptoms are maintained under control with antisecretory agents, mainly gastric proton pump inhibitors (PPIs). Although impaired oesophageal motility may partly underlie the pathophysiology of GORD, the use of prokinetic agents has been found to be unsatisfactory. To date, novel pharmacological approaches for GORD are mainly related to the control of transient lower oesophageal sphincter (LOS) relaxations (TLOSRs). The majority of patients with GORD have reflux episodes during TLOSRs, which are evoked by gastric distension, mainly occurring after ingestion of a meal. Patients with reflux disease with normal peristalsis and without or with mild erosive disease could potentially benefit from anti-TLOSR therapy. This therapy might also be of value to treat some severe forms of esophagitis in combination with PPIs. GABA-B-receptor agonists are the most promising class of agents identified so far for TLOSR control. The GABA-B-receptor agonist, baclofen, is the most effective compound in inhibiting TLOSRs in humans. Since baclofen has several CNS adverse effects, novel orally available GABA-B agonists are needed for effective and well tolerated treatment of GORD. Endogenous or exogenous cholecystokinin (CCK) causes a reduction in LOS pressure, an increase in TLOSR frequency and a reduction in gastric emptying. In healthy volunteers and patients with GORD, loxiglumide, a selective CCK1-receptor antagonist, was found to reduce the rate of TLOSRs, although its effect on postprandial acid reflux may be modest. Orally effective CCK antagonists are not marketed to date. The anticholinergic agent atropine, given to healthy volunteers and patients with GORD, markedly reduced the rate of TLOSRs. Because of severe gastrointestinal (and other) adverse effects of anticholinergics, including worsening of supine acid clearance and constipation, it is unlikely that this class of drugs will have a future as anti-TLOSR agents on a routine basis. In spite of their effectiveness in reducing TLOSR rate, untoward adverse effects, such as addiction and severe constipation, currently limit the use of morphine and other opioid mu-receptor agonists. The same applies to nitric oxide synthase inhibitors, which are associated with marked gastrointestinal, cardiovascular, urinary and respiratory adverse effects. Animal studies provide promising evidence for the use of cannabinoid receptor 1 agonists, by showing potent inhibition of TLOSRs in the dog, thus opening a new route for clinical investigation in humans. A better understanding of TLOSR pathophysiology is a necessary step for the further development of novel drugs effective for anti-reflux therapy.

Review article: new pharmacological agents for the treatment of gastro-oesophageal reflux disease

Proton pump inhibitors, which act at the terminal point of acid secretion--the H+, K+-ATPase--are currently the most effective pharmacological treatments available for reflux disease. Despite the efficacy of the proton pump inhibitors, there is still potential for clinical improvement in gastro-oesophageal reflux disease pharmacotherapy. Faster onset of complete acid inhibition and improved duration of efficacy are two potential areas for improvement A number of novel pharmaceutical agents are currently undergoing clinical evaluation for the treatment of gastro-oesophageal reflux disease. These include transient lower oesophageal sphincter relaxation-reducing agents, serotonergic agents/prokinetics, potassium-competitive acid blockers, mucosal protectants, histamine H3 agonists and anti-gastrin agents. One or more of these drug groups may represent the future medical therapy for gastro-oesophageal reflux disease, should they prove effective in the clinical setting. This review summarizes the state of the art with these agents.

Triptans and gastric accommodation: pharmacological and therapeutic aspects

In the past decade, several studies have reported a significant delay of gastric emptying induced by the anti-migraine agent sumatriptan (a 5-hydroxytryptamine (5-HT)1B/D receptor agonist) in healthy human beings. In patients with functional dyspepsia, sumatriptan improves gastric accommodation after food consumption and reduce perception of gastric distension, hence relieving epigastric symptoms. Recent studies have established that impaired accommodation after food consumption is a major patho-physiological mechanism in functional dyspepsia and restoration of accommodation is considered to be a potential therapeutic target. The precise site of action of sumatriptan in humans is at present unknown, although recent studies carried out using a canine model indicate that sumatriptan exerts its action on gastric accommodation through 5-HT1B receptors, since both GR127935 and SB216641 (respectively, non selective 5-HT1B/D and selective 5-HT1B receptor antagonists) fully antagonised the effects of sumatriptan. Gastric relaxation and enhanced accommodation to a distending stimulus seem to be a class effect of triptans, since it occurs not only with sumatriptan, but also with second-generation triptans (rizatriptan and naratriptan), at least in a canine model. In dyspeptic patients, administration of triptans would be able to restore gastric accommodation after a meal and to improve symptoms of early satiety, confirming the therapeutic potential of 5-HT1B/D receptor agonists in functional dyspepsia.

Cannabinoid receptor agonism inhibits transient lower esophageal sphincter relaxations and reflux in dogs

BACKGROUND & AIMS

Transient lower esophageal sphincter relaxations (TLESRs) are the major cause of gastroesophageal acid reflux, and are triggered by postprandial gastric distention. Stimulation of GABA(B) receptors potently inhibits triggering of TLESR by gastric loads. The functional similarity between GABA(B) and cannabinoid receptors (CBRs) prompted us to study the role of CBRs on mechanisms of gastric distention-induced TLESRs.

METHODS

Gastric nutrient infusion and air insufflation was performed during gastroesophageal manometry in conscious dogs. The effects of the CBR agonist WIN 55,212-2 were assessed alone and in combination with the CBR1 antagonist SR141716A or the CBR2 antagonist SR144528. The effects of WIN 55,212-2 were also studied on firing of gastric vagal mechanosensitive afferents in an isolated preparation of ferret stomach.

RESULTS

WIN 55,212-2 (57 nmol/kg) inhibited the occurrence of TLESR after gastric loads by 80% (P < 0.01). The latency to the first TLESR after the load was prolonged (P < 0.001), and the occurrence of swallowing was reduced (P < 0.05). The CBR1 antagonist SR141716A reversed the effects of WIN 55,212-2, whereas the CBR2 antagonist SR144528 did not. The CBR1 antagonist alone increased occurrence of TLESR (P < 0.05). The responses of gastric vagal mechanoreceptors to distention were unaffected by WIN 55,212-2 at a concentration of 3 micromol/L.

CONCLUSIONS

Exogenous and endogenous activation of the CBR1 receptor inhibits TLESRs. The effects of CBR1 are not mediated peripherally on gastric vagal afferents, and therefore are most likely in the brain stem.