Cisapride. An updated review of its pharmacology and therapeutic efficacy as a prokinetic agent in gastrointestinal motility disorders

Integrated Isogenic Human Induced Pluripotent Stem Cell-Based Liver and Heart Microphysiological Systems Predict Unsafe Drug-Drug Interaction

Three-dimensional (3D) microphysiological systems (MPSs) mimicking human organ function in vitro are an emerging alternative to conventional monolayer cell culture and animal models for drug development. Human induced pluripotent stem cells (hiPSCs) have the potential to capture the diversity of human genetics and provide an unlimited supply of cells. Combining hiPSCs with microfluidics technology in MPSs offers new perspectives for drug development. Here, the integration of a newly developed liver MPS with a cardiac MPS—both created with the same hiPSC line—to study drug–drug interaction (DDI) is reported. As a prominent example of clinically relevant DDI, the interaction of the arrhythmogenic gastroprokinetic cisapride with the fungicide ketoconazole was investigated. As seen in patients, metabolic conversion of cisapride to non-arrhythmogenic norcisapride in the liver MPS by the cytochrome P450 enzyme CYP3A4 was inhibited by ketoconazole, leading to arrhythmia in the cardiac MPS. These results establish integration of hiPSC-based liver and cardiac MPSs to facilitate screening for DDI, and thus drug efficacy and toxicity, isogenic in the same genetic background.

Could prokinetic agents protect long-term nasogastric tube-dependent patients from being hospitalized for pneumonia? A nationwide population-based case-crossover study

Background

Some studies have indicated that the use of prokinetic agents may reduce pneumonia risk in some populations. Nasogastric tube insertion is known to increase the risk of pneumonia because it disrupts lower esophageal sphincter function. The aim of this study was to evaluate whether prokinetic agents could protect long-term nasogastric tube-dependent patients in Taiwan from being hospitalized for pneumonia.

Methods

A case-crossover study design was applied in this study. Long-term nasogastric tube-dependent patients who had a first-time admission to a hospital due to pneumonia from 1996 to 2013 that was recorded in the Taiwan National Health Insurance Research Database were included. The case period was set to be 30 days before admission, and two control periods were selected for analysis. Prokinetic agent use during those three periods was then assessed for the included patients. Conditional logistic regression was used to calculate the odds ratio (OR) for pneumonia admission with the use of prokinetic agents.

Results

A total of 639 first-time hospitalizations for pneumonia among patients with long-term nasogastric tube dependence were included. After adjusting the confounding factors for pneumonia, no negative association between prokinetic agent use and pneumonia hospitalization was found, and the adjusted OR was 1.342 (95% CI 0.967–1.86). In subgroup analysis, the adjusted ORs were 1.401 (0.982–1.997), 1.256 (0.87–1.814), 0.937 (0.607–1.447) and 2.222 (1.196–4.129) for elderly, stroke, diabetic and parkinsonism patients, respectively.

Conclusion

Prokinetic agent use had no negative association with pneumonia admission among long-term nasogastric tube-dependent patients in Taiwan.

Drug-induced QT prolongation: Concordance of preclinical anesthetized canine model in relation to published clinical observations for ten CiPA drugs

INTRODUCTION

The Comprehensive In Vitro Proarrhythmia Assay (CiPA) initiative differentiates torsadogenic risk of 28 drugs affecting ventricular repolarization based on multiple in vitro human derived ionic currents. However, a standardized prospective assessment of the electrophysiologic effects of these drugs in an integrated in vivo preclinical cardiovascular model is lacking. This study questioned whether QTc interval prolongation in a preclinical in vivo model could detect clinically reported QTc prolongation and assign torsadogenic risk for ten CiPA drugs.

METHODS

An acute intravenous administered ascending dose anesthetized dog cardiovascular model was used to assess QTc prolongation along with other electrocardiographic (PR, QRS intervals) and hemodynamic (heart rate, blood pressures, left ventricular contractility) parameters at plasma concentrations spanning and exceeding clinical exposures. hERG current block potency was characterized using IC₅₀ values from automated patch clamp.

RESULTS

All eight drugs eliciting clinical QTc prolongation also delayed repolarization in anesthetized dogs at plasma concentrations within four-fold clinical exposures. In vitro QTc safety margins (defined based on clinical C_max values/plasma concentrations eliciting statistically significant QTc prolongation in dogs) were lower for high vs intermediate torsadogenic risk drugs. In comparison, hERG IC₁₀ values represented as total drug concentrations were better predictors of preclinical QTc prolongation than hERG IC₅₀ values.

CONCLUSION

There was good concordance for QTc prolongation in the anesthetized dog model and clinical torsadogenic risk assignment. QTc assessment in the anesthetized dog remains a valuable part of a more comprehensive preclinical integrated risk assessment for delayed repolarization and torsadogenic risk as part of a global cardiovascular evaluation.

Childhood gastroparesis is a unique entity in need of further investigation

BACKGROUND

Despite increasing knowledge regarding gastroparesis (GP) in adults, little is known regarding the incidence, prevalence, and natural history of childhood GP. Exacerbating the knowledge gap in pediatric GP is both the lack of normative data for gastric emptying scintigraphy in children and lack of GP-specific pediatric reported outcome measures.

PURPOSE

The aim of this article was to review the available literature on pediatric GP and identify similarities and differences with studies in adults. We performed a comprehensive search in MEDLINE and Google Scholar from inception to April 2019 for articles published in English using the following combination of keywords: gastroparesis, pediatric gastroparesis, outcomes, metoclopramide, erythromycin, domperidone, cisapride, and gastric neurostimulator. The limited available pediatric data, often retrospective, suggest marked differences between adult and pediatric GP in several aspects including etiology, concomitant co-morbidities (eg, psychiatric disorders), clinical symptom presentation, diagnostic evaluation, response to therapies, and clinical outcome. Further research in pediatric GP is needed and holds the promise to further elucidate the mechanisms of this disorder in children and lead to pediatric-focused therapies.

Antipsychotics and cardiovascular risk: A case/non-case study

Severe mental disorders have been reported to be associated with an increased cardiovascular risk. To measure the potential risk excess as compared, not with the baseline cardiovascular risk for the general population, but with the cardiovascular risk associated with drug iatrogenia. 197 reported cases of cardiovascular adverse reaction to antipsychotic drugs as compared to the reported cases of this type of adverse reactions to drugs other than antipsychotics entered in the Spanish Pharmacovigilance System database (FEDRA) (1995-2018) in an observational case/non-case study. Risk estimates of association were reporting odds ratio (ROR), and, chi-square test (χ²). Overall disproportionality for the whole drug class was found [ROR 2.3 (95% CI 2.0-2.7)], χ² = 127.07]. When the two types of antipsychotics (typical and atypical) were analysed separately, we also found statistically significant disproportionality, and this disproportionality is similar between both groups, with disproportionality measures around 2.30, with the confidence intervals not including the 1. The disproportionality observed suggests a risk excess that might be greater than expected, which holds particularly true for torsade de pointes, sudden death and cardiac arrhythmias in patients treated with any of the two types of antipsychotics. There was no significant risk for ischaemic heart disease.

Observations on conducting whole-cell patch clamping of the hERG cardiac K+ channel in pure human serum

Inhibition of the human ether-a-go-go-related gene (hERG) K⁺ channel by drugs leads to QT prolongation on the electrocardiogram and can result in serious cardiac arrhythmia. For this reason, screening of drugs on hERG is mandatory during the drug development process. Patch clamp electrophysiology in a defined physiological saline solution (PSS) represents the standard method for assaying drug effects on the channel. To make the assay more translatable to clinical studies, we have conducted whole-cell patch clamping of hERG using pure human serum as the extracellular medium. Pure human serum had little effect on the hERG channel waveform or the current-voltage relationship when compared to PSS. hERG current recordings were highly stable in serum at room temperature, but prolonged recordings at the physiological temperature required prior heat inactivation of the serum. Compared to PSS, the IC₅₀ values, conducted at room temperature, of the classic hERG blocking drugs cisapride, moxifloxacin, and terfenadine were shifted to the right by an extent predicted by their known plasma protein binding, but we did not detect any differences in IC₅₀ s between male and female serum. Total plasma levels of these drugs associated with clinical QT prolongation corresponded to small (<15%) inhibition of hERG current in pure serum suggesting that minor inhibition of the channel leads to observable pharmacodynamic effects. Conducting whole-cell patch clamping of hERG in human serum has the potential to make the assay more translatable to clinical studies and improve its predictive value for safety testing. Copyright © 2016 John Wiley & Sons, Ltd.

Synergistic effect between 5-HT4 receptor agonist and phosphodiesterase 4-inhibitor in releasing acetylcholine in pig gastric circular muscle in vitro

5-HT4 receptor agonists have a gastroprokinetic effect by facilitating acetylcholine release from cholinergic nerves innervating gastrointestinal smooth muscle. The role of phosphodiesterase (PDE) 4 in the signal transduction pathway of the 5-HT4 receptors located on the cholinergic neurons towards the circular muscle layer in pig stomach was investigated by analysis of acetylcholine release. Circular muscle strips were prepared from pig proximal stomach and tritium outflow, induced by electrical field stimulation, was studied as a marker for acetylcholine release after incubation with [(3)H]-choline. The PDE4-inhibitor roflumilast concentration-dependently (0.1-1µM) enhanced the facilitating effect of a submaximally effective concentration of the 5-HT4 receptor agonist prucalopride (0.01µM) on electrically induced acetylcholine release. Roflumilast (0.3µM) enhanced acetylcholine release per se but in the combined presence of roflumilast and prucalopride, acetylcholine release was enhanced more than the sum of the effect of the 2 compounds alone. The 5-HT4 receptor agonist velusetrag concentration-dependently (0.01-0.1µM) enhanced acetylcholine release; the effect of the minimally effective concentration (0.01µM) was significantly enhanced by 1µM of the PDE4-inhibitor rolipram, again to a level higher than the sum of the effect of the 2 compounds alone. The synergistic effect between 5-HT4 receptor agonists and PDE4-inhibitors demonstrates that the intracellular pathway of the 5-HT4 receptors located on cholinergic neurons towards pig gastric circular muscle is controlled by PDE4. Combining a 5-HT4 receptor agonist with a PDE4-inhibitor might thus enhance its gastroprokinetic effect.

Randomized clinical trial: effect of the 5-HT4 receptor agonist revexepride on reflux parameters in patients with persistent reflux symptoms despite PPI treatment

BACKGROUND

Approximately, 20-30% of patients with gastro-esophageal reflux disease (GERD) experience persistent symptoms despite treatment with proton pump inhibitors (PPIs). These patients may have underlying dysmotility; therefore, targeting gastric motor dysfunction in addition to acid inhibition may represent a new therapeutic avenue. The aim of this study was to assess the pharmacodynamic effect of the prokinetic agent revexepride (a 5-HT4 receptor agonist) in patients with GERD who have persistent symptoms despite treatment with a PPI.

METHODS

This was a phase II, exploratory, multicenter, randomized, placebo-controlled, double-blind, parallel-group study in patients with GERD who experienced persistent symptoms while taking a stable dose of PPIs (ClinicalTrials.gov identifier: NCT01370863). Patients were randomized to either revexepride (0.5 mg, three times daily) or matching placebo for 4 weeks. Reflux events and associated characteristics were assessed by pH/impedance monitoring and disease symptoms were assessed using electronic diaries and questionnaires.

KEY RESULTS

In total, 67 patients were enrolled in the study. There were no significant differences between study arms in the number, the mean proximal extent or the bolus clearance times of liquid-containing reflux events. Changes from baseline in the number of heartburn, regurgitation, and other symptom events were minimal for each treatment group and no clear trends were observed.

CONCLUSIONS & INFERENCES

No clear differences were seen in reflux parameters between the placebo and revexepride groups.

Oral domperidone has no additional effect on chronic functional constipation in children: a randomized clinical trial

BACKGROUND

Chronic constipation represents a common problem in children. The treatment of functional constipation is challenging. Some studies have investigated the effect of prokinetic agents as potential therapies for motility disorders of the lower gastrointestinal tract with paradoxical results. The present study aimed to investigate the effect of oral domperidone in the treatment of chronic functional constipation in children.

METHOD

A total of 105 children with chronic functional constipation (according to Rome III criteria) who were referred to the Pediatric Gastroenterology Clinic were recruited in this double-blind randomized clinical trial. The study subjects were randomly divided into two groups, the first of which received polyethylene glycol (PEG) solution 0.6 g/kg/day two times a day for 6 months and domperidone syrup 0.15 mL/kg three times a day for 3 months (case group) while the second one received PEG with the same dose for 6 months and placebo for 3 months with the same dose (control group). The two groups were compared regarding their symptoms and Rome III criteria through 1, 3, and 6 months following therapy. Primary outcome was response to treatment, and a response was defined as decrease in signs and symptoms that did not fulfill Rome III criteria. Secondary outcome measures were side effects during the course of treatment.

RESULTS

A significant difference was observed both before and after PEG and domperidone treatment and before and after PEG and placebo treatment regarding Rome III criteria. There was no significant difference in response to treatment between the two study groups during 1 (p = 1), 3 (p = 0.799), and 6 (p = 0.403) month follow up periods. Also, the two groups were not significantly different regarding the Rome III criteria during the mentioned follow up periods. There were no side effects during the course of treatment.

CONCLUSION

There was no additional effect of domperidone as adjunct to PEG in the treatment of children with constipation.

The relation between symptom improvement and gastric emptying in the treatment of diabetic and idiopathic gastroparesis

OBJECTIVES

The relationship between symptom improvement (SI) and acceleration of gastric emptying (GE) for different drugs used in the treatment of idiopathic and diabetic gastroparesis is uncertain. In this paper we examined the study-specific correlations between SI and GE, and we performed a meta-regression analysis of the association across multiple studies.

METHODS

The MEDLINE database (1,946 to present) was searched, and only controlled trials or trials with an established effective comparator that compared both SI and GE were included.

RESULTS

Studies were identified for metoclopramide (n=6), domperidone (n=6), cisapride (n=14), erythromycin (n=3), botulinum toxin (n=2), and levosulpiride (n=3). Even though most drugs concomitantly improved symptoms and accelerated GE, no study reported a significant correlation between SI and GE. Moreover, a correlation analysis over all studies using meta-regression did not show a significant relationship between SI and GE. Our findings need to be qualified by inconsistencies in study methods, which is a limitation but also suggests that our findings are robust to methodological factors.

CONCLUSIONS

In this review, no evidence of a relationship between SI and GE was identified for different drugs used for the treatment of gastroparesis. This finding questions the use of GE measurement to direct drug development for gastroparesis.

Botulinum toxin type A for the treatment of gastroparesis in Parkinson's disease patients

Gastroparesis is a very common non-motor feature in Parkinson's disease (PD) patients. However, treatment options are limited and difficult. We present 2 cases of PD patients with excellent response to botulinum toxin type A as treatment for PD-related gastroparesis.

Effects of mosapride on esophageal functions and gastroesophageal reflux

BACKGROUND AND AIM

A substantial number of patients with gastroesophageal reflux disease show symptomatic resistance to high-dose proton pump inhibitors. In those cases, prokinetics are possible candidates for treatment. The aim of the present study was to determine whether mosapride, a prokinetic agent, stimulates esophageal functions, and prevents acidic and non-acidic gastroesophageal reflux.

METHODS

Normal volunteers (nine and 13 for two experiments, respectively) were enrolled. Salivary secretion, esophageal peristaltic contractions, and resting lower esophageal sphincter pressure with and without mosapride administration were recorded using a cross-over protocol. Post-prandial acidic and non-acidic reflux levels were also recorded.

RESULTS

Mosapride at a standard dose of 15 mg/day did not stimulate salivary secretion or any esophageal motor functions. It also failed to prevent acidic and non-acidic post-prandial gastroesophageal reflux.

CONCLUSIONS

Mosapride at 15 mg/day, a standard dose in Japan, did not change the esophageal motility and salivary secretion in healthy volunteers. Future study on a larger number of individuals with higher dose of mosapride is worthwhile.

Functional dyspepsia

Dyspepsia is a common term used for a heterogeneous group of abdominal symptoms. Functional dyspepsia (FD) is the focus of this review. The 2006 Rome III criteria defined FD and its subgroups, postprandial distress syndrome (PDS) and epigastric pain syndrome (EPS). FD is a very common condition with a high prevalence throughout the world, adversely affecting the quality of life of patients. The pathophysiology of FD has been under investigation during the past two decades. Multiple mechanisms such as abnormal gastric emptying, visceral hypersensitivity, impaired gastric accommodation, and central nervous system factors are likely involved. Several tests are available for the assessment of various physiologic functions possibly involved in the pathogenesis of FD, and some of these could be used in clinical practice, helping to understand the abnormalities underlining patients' complaints. Currently, the possibilities of pharmacological therapy for FD are still limited, however, experience of using prokinetics, tricyclic antidepressants, selective serotonin-reuptake inhibitors (SSRIs), proton-pump inhibitors (PPIs), and several alternative techniques has been accumulated. The different combinations of alterations in physiologic gastrointestinal and central nervous system functions result in the very heterogeneous nature of FD so combined approaches to these patients could be beneficial in challenging cases.

Electrophysiological characterization of isolated human atrial myocytes exposed to tegaserod

Tegaserod (Teg), a 5-hydroxytryptamine type-4 (5-HT(4)) receptor partial agonist, represents a novel treatment for irritable bowel syndrome with constipation and chronic constipation. Cardiovascular safety data from pooled clinical studies showed a signal suggestive of increased occurrence of ischaemic cardiovascular events in patients exposed to Teg versus placebo. Thereafter, marketing of Teg was suspended in the USA and other countries. The clinical data did not demonstrate a causative effect but raised questions of whether a non-recognized effect on the heart was present. Our aim was to evaluate for arrhythmogenic potential of Teg on human cardiomyocytes. Cells isolated from human atrial specimens during cardiac surgery were used to assess the effects of Teg (1, 10, 30 and 100 nM) on action potential and I(f) (funny current) by patch-clamp technique. Results showed that Teg (at all concentrations tested) did not significantly affect action potential characteristics of atrial myocytes when driven at different rates (0.2, 0.5 and 1 Hz). In contrast, 5HT significantly prolonged action potential duration (1 and 10 nM) and caused cell un-excitability (100 nM). Teg, at the highest concentration tested (100 nM, corresponding to 10 times C(max), produced by the recommended dose of 6 mg b.i.d.) increased the I(f) amplitude and caused a shift of its activation curve. This effect of a high concentration of Teg is not considered clinically relevant. When evaluated on single human atrial cells, Teg does not appear to exhibit arrhythmogenic properties, as it did not affect the action potential profile.

Atypical antipsychotic drugs and the risk of sudden cardiac death

BACKGROUND

Users of typical antipsychotic drugs have an increased risk of serious ventricular arrhythmias and sudden cardiac death. However, less is known regarding the cardiac safety of the atypical antipsychotic drugs, which have largely replaced the older agents in clinical practice.

METHODS

We calculated the adjusted incidence of sudden cardiac death among current users of antipsychotic drugs in a retrospective cohort study of Medicaid enrollees in Tennessee. The primary analysis included 44,218 and 46,089 baseline users of single typical and atypical drugs, respectively, and 186,600 matched nonusers of antipsychotic drugs. To assess residual confounding related to factors associated with the use of antipsychotic drugs, we performed a secondary analysis of users of antipsychotic drugs who had no baseline diagnosis of schizophrenia or related psychoses and with whom nonusers were matched according to propensity score (i.e., the predicted probability that they would be users of antipsychotic drugs).

RESULTS

Current users of typical and of atypical antipsychotic drugs had higher rates of sudden cardiac death than did nonusers of antipsychotic drugs, with adjusted incidence-rate ratios of 1.99 (95% confidence interval [CI], 1.68 to 2.34) and 2.26 (95% CI, 1.88 to 2.72), respectively. The incidence-rate ratio for users of atypical antipsychotic drugs as compared with users of typical antipsychotic drugs was 1.14 (95% CI, 0.93 to 1.39). Former users of antipsychotic drugs had no significantly increased risk (incidence-rate ratio, 1.13; 95% CI, 0.98 to 1.30). For both classes of drugs, the risk for current users increased significantly with an increasing dose. Among users of typical antipsychotic drugs, the incidence-rate ratios increased from 1.31 (95% CI, 0.97 to 1.77) for those taking low doses to 2.42 (95% CI, 1.91 to 3.06) for those taking high doses (P<0.001). Among users of atypical agents, the incidence-rate ratios increased from 1.59 (95% CI, 1 .03 to 2.46) for those taking low doses to 2.86 (95% CI, 2.25 to 3.65) for those taking high doses (P=0.01). The findings were similar in the cohort that was matched for propensity score.

CONCLUSIONS

Current users of typical and of atypical antipsychotic drugs had a similar, dose-related increased risk of sudden cardiac death.

The cardiovascular safety profile of renzapride, a novel treatment for irritable bowel syndrome

The cardiac safety of renzapride, a novel benzamide currently under clinical development for the treatment of irritable bowel syndrome, was investigated in a four-way randomized crossover electrocardiographic clinical study in healthy human subjects and also in an in vitro cardiac conductivity study in sheep isolated Purkinje fibres. The primary endpoint in the clinical study was prolongation of the individually corrected QT interval (QTci). No clinically or statistically significant prolongation of QTci after 4 or 20 mg renzapride compared with placebo was observed. The relative effects of renzapride and cisapride in the in vitro study showed that the cardiac action potential duration was unaltered by 0.2 and 2 microM renzapride, shortened by 20 microM renzapride, and prolonged by 1 microM cisapride. Cisparide was also a 1000-fold more potent inhibitor of human ether-a-go-go related gene (hERG) channels in HEK293 cells than renzapride. These studies indicate that therapeutic doses of renzapride are unlikely to prolong cardiac action potentials and, therefore, are also unlikely to cause cardiac arrhythmias in clinical use.

Gastrointestinal motility after digestive surgery

Gastrointestinal (GI) motility dysfunction is a common complication of any abdominal surgical procedure. During fasting, the upper GI tract undergoes a cyclic change in motor activity, called the interdigestive migrating motor contraction (IMC). The IMC is divided into four phases, with phase III having the most characteristic activity. After digestive surgery, GI motility dysfunction shows a lack of a fed response, less phase II activity, more frequent phase III activity of the IMC, and some phase III activity migrating orally. Postoperative symptoms have been related to motor disturbances, such as interrupted or retrograde phase III or low postprandial activity. The causes of GI disorder are autonomic nervous dysfunction and GI hormone disruptions. The administration of a motilin agonist can induce earlier phase III contractions in the stomach after pancreatoduodenectomy. For nervous dysfunction, an inhibitory sympathetic reflux is likely to be important in postoperative motility disorders. Until recently, treatment for gut dysmotility has consisted of nasogastric suction, intravenous fluids, and observation; however, more effective treatment methods are being reported. Recent discoveries have the potential to decrease postoperative gut dysmotility remarkably after surgery.

The effects of tegaserod on oesophageal function and bolus transport in healthy volunteers: studies using concurrent high-resolution manometry and videofluoroscopy

BACKGROUND

Tegaserod is a partial 5-hydroxytryptamine 4 receptor agonist with prokinetic effects on the gastrointestinal tract, its effects on oesophageal function are unknown.

AIM

A randomized, placebo controlled, double-blind trial assessed the effect of tegaserod on the oesophagus in healthy, asymptomatic subjects.

METHOD

A 7-day course of tegaserod 6 mg b.d. vs. placebo was prescribed (n = 17/21 completed both phases of study). High-resolution manometry and pH measurements were performed before and after a test meal. Bolus transport of liquids and solids was studied by high-resolution manometry and videofluoroscopy.

RESULTS

Tegaserod had no effect on lower oesophageal sphincter pressure compared with placebo, peristaltic velocity increased (P < 0.001) and distal contractile pressure decreased slightly (P < 0.05). Transient lower oesophageal sphincter relaxations and reflux were infrequent regardless of treatment. During the studies of bolus transport, high-resolution manometry revealed that tegaserod promoted mid-oesophageal contractility (P < 0.02) and shortened the 'proximal transition zone' (P < 0.05), the level where bolus escape occurred most frequently. These effects had no effect on liquid bolus transport; however a non-significant trend to improved solid bolus transport was observed (66% vs. 31%;P = 0.07).

CONCLUSION

Tegaserod did not alter lower oesophageal sphincter pressure, but had significant effects on peristaltic function. High-resolution manometry promoted mid-oesophageal contractility during bolus transport. This effect was associated with a non-significant trend to improved solid bolus transit.

Assessing the proarrhythmic potential of drugs: current status of models and surrogate parameters of torsades de pointes arrhythmias

Torsades de pointes (TdP) is a potentially lethal cardiac arrhythmia that can occur as an unwanted adverse effect of various pharmacological therapies. Before a drug is approved for marketing, its effects on cardiac repolarisation are examined clinically and experimentally. This paper expresses the opinion that effects on repolarisation duration cannot directly be translated to risk of proarrhythmia. Current safety assessments of drugs only involve repolarisation assays, however the proarrhythmic profile can only be determined in the predisposed model. The availability of these proarrhythmic animal models is emphasised in the present paper. It is feasible for the pharmaceutical industry to establish one or more of these proarrhythmic animal models and large benefits are potentially available if pharmaceutical industries and patient-care authorities embraced these models. Furthermore, suggested surrogate parameters possessing predictive power of TdP arrhythmia are reviewed. As these parameters are not developed to finalisation, any meaningful study of the proarrhythmic potential of a new drug will include evaluation in an integrated model of TdP arrhythmia.

Important Facts About Intestinal Feeding Tube Placement

Enteral feeding is desirable when the gastrointestinal tract is functional because it allows better use of nutrients, is safer, and is more cost-effective than parenteral nutrition. Feeding through a gastric tube, however, is often not feasible in severely ill adults and children because of gastric paresis leading to recurrent episodes of gastroesophageal reflux with the risk of subsequent aspiration. Feeding into the small intestine (duodenum or jejunum) through a nasointestinal tube, therefore, is preferred. Unfortunately, no method of enteral feeding is risk free. This literature review addresses the following 10 topics: (a) the reasons why nasointestinal tube feeding is better tolerated by some patients, (b) candidates for nasointestinal tube feeding, (c) options for selecting nasointestinal tubes, (d) recommended methods for predicting the distance to insert nasointestinal tubes, (e) recommended methods for placing nasointestinal tubes, (f) how promotility medications work and whether they facilitate nasointestinal tube placement, (g) nasointestinal tube placement error rate, (h) methods of determining the internal location of nasointestinal tubes, (i) complications associated with nasointestinal tube use, and (j) other pertinent issues surrounding feeding through nasointestinal tubes. The available research evidence is summarized and recommendations for future work are suggested.

Effect of Anticholinergics (Atropine, Glycopyrrolate) and Prokinetics (Metoclopramide, Cisapride) on Gastric Motility in Beagles and Labrador Retrievers

The effect of atropine, glycopyrrolate, metoclopramide and cisapride on the antral motility was investigated in eight dogs (four Beagles and four Labradors) using passive telemetry. Both anticholinergics induced a pronounced and lasting reduction of the intensity and frequency of the contractions. A definite dose-related inhibition of the antral motility was seen in Beagles, similar for both active substances. Low doses of atropine (0.02 mg/kg BW i.m.) and glycopyrrolate (0.005 mg/kg BW i.m.) completely inhibited the gastric motility for at least 30 min, whereas higher doses (0.04 or 0.01 mg/kg BW) caused a cessation of activity for more than 3 h. In Labradors, the effects of both active substances were not so dose related and the effect of glycopyrrolate lasted at least 6 h, whereas the effect of atropine gradually decreased after 3 h. A distinct breed difference regarding the effect of the two prokinetics on the antral motility was also observed. In Beagles, the prokinetics, at a low dose (metoclopramide 0.3 mg/kg BW, cisapride 0.2 mg/kg BW), resulted in a significant increase in the amplitude integral. Higher doses (metoclopramide 0.6 mg/kg BW, cisapride 0.5 mg/kg BW) also increased the integrals of the pressure profiles, but significantly less than with the lower doses. In Labradors, both medications, mainly at higher doses, resulted in an increase of the contraction amplitudes. The low dose had no (cisapride) or only a transient effect (metoclopramide). The frequency of the antral contractions was not at all influenced by cisapride, and only in Beagles metoclopramide resulted in a dose-related increase. It is not clear if the different results in Labradors and Beagles are because of breed or body weight.

Co-dispensing of contraindicated medications in patients using cisapride in Italy

PURPOSE

To investigate the co-dispensing of contraindicated medications in patients using cisapride in an Italian population.

METHODS

The study included patients who had at least one cisapride prescription dispensed between 1 April 1997 and 30 September 2000. The proportion of cisapride users with concomitant medications, the proportion of prescriptions of cisapride with an overlapping dispensing of a contraindicated medication and the proportion of person-days of cisapride use concomitant with contraindicated medications, were calculated.

RESULTS

In the 4-year study period, 249,740 total cisapride prescriptions, which corresponded to 382,835 packages, were dispensed to 91,204 users (52,442 female, 57.5%). Concomitant use of contraindicated drugs was identified in 4403 cisapride users (4.83%). Throughout the study period, there was an increase in the proportion of cisapride users with contraindicated co-prescriptions: 4.29% in 1997, 4.99% in 1998, 5.15% in 1999, but a decline to 3.34% in 2000. In each year, this figure was higher in males, with the highest proportion reported in 1999 (5.50%). A total of 7215 cisapride prescriptions (2.85%) were concomitant with contraindicated drugs, ranging from 2.27% in September 1998 to 3.55% in January 1999. Cisapride prescriptions were most frequently associated with macrolide antibiotics (1.14%) and class III antiarrhythmics (1.03%).

CONCLUSIONS

In the period 1997-2000, a substantial proportion of cisapride prescriptions were concomitant with contraindicated medications. In Italy in 1998, the National Health Authority issued a bulletin warning about the risk of serious arrhythmias after concomitant use of contraindicated drugs. Despite this warning, there was no reduction in contraindicated drug uses.

Promotility medications--now and in the future

Gastrointestinal promotility drugs stimulate smooth muscle contractions to enhance gastric emptying and small and large bowel transit. Currently available drug classes with prokinetic properties include antidopaminergic agents, serotonergic agents, and motilin-receptor agonists. Due to moderate prokinetic effects, poor symptomatic responses and the presence of adverse effects, there is a clear need for new classes of prokinetics. Several newer prokinetic drugs and drug classes are currently under evaluation. Selecting candidate agents and designing the appropriate therapeutic trials is hampered by the lack of insight in the pathophysiology of motility-related symptoms. As gastrointestinal motor disorders are chronic, relapsing, and remitting disorders, it seems desirable that studies with candidate prokinetic drugs establish a long-term efficacy and not only short-term effects on gastrointestinal functions.

Usage of the claim database of national health insurance programme for analysis of cisapride-erythromycin co-medication in Taiwan

PURPOSE

This study aimed to use the National Health Insurance Research Database, Taiwan for risk analysis of concomitant use of cisapride and erythromycin.

METHODS

The sample consisted of subjects identified in the Outpatient Sampling Database (OSD) and Longitudinal Health Insurance Database 2000 (LHID 2000), derived from the original claim data of the National Health Insurance Research Database, Taiwan.

RESULTS

According to the LHID 2000, a total of 464 individuals experienced 685 episodes of cisapride-erythromycin co-medication prescribed by 295 physicians, revealing a prevalence of 4.5% concomitant use, with higher prevalence in clinics (9.2%) than in other medical institutes (3.7-5.4%). Among the co-medication episodes, 81.9% and 61.2% were prescribed from the same health institutes and by the same physicians, respectively. No medical record of cardiac arrhythmias was found among these patients in 2001 and 2002, probably due to the fact that 78.9% of the 464 individuals were under age 16, 84.0% had short exposure duration (1-4 days) and 98.0% of the episodes were prescribed with a cisapride dose of less than 0.8 mg/kg/day.

CONCLUSIONS

Findings from this study suggest that there exists an urgent need for accreditation in terms of pharmacovigilance of clinical sites and their practicing physicians for the prevention of irrational concomitant prescription in Taiwan. Our findings also indicate that it is necessary to investigate other possible conditions of potentially dangerous co-medication in Taiwan and other developing countries.

Therapieoptionen der chronischen Obstipation

Chronic constipation is a widespread disease affecting up to 25 percent of the population in western countries. The symptoms associated with constipation may lead to a heavy burden and a decrease in quality of life. The therapy of chronic constipation is based upon its type and severity. Patients with normal transit may benefit from lifestyle measures including dietetic advice. However, almost none of these measures has been validated in a controlled trial. Bulk forming laxatives such as psyllium seeds and probiotics have a moderate evidence (Grade B). In certain cases, the use of osmotic laxatives, e. g. polyethylene glycol solutions (Grade A), is necessary. Tegaserod, a selective agonist of the serotonine subtype 4 (5-HT(4)), has a good evidence to treat constipation (Grade A). Patients with slow-transit constipation (transit-time over 72 hours) are dependent on osmotic (polyethylene glycol solutions, Grade A) and stimulant laxatives (bisacodyl, Grade C). Patients who suffer from defecatory disorders (outlet constipation) should be treated with bulk forming laxatives (Grade B) together with suppositories (e. g. CO(2)-suppositories) and enemas.

Mechanisms by which food intake elevates circulating levels of hyaluronan in humans

OBJECTIVES

Plasma hyaluronan is a potentially useful clinical test, especially in liver disease. It rises after eating, but mechanisms by which this occurs are not known. The study aimed at defining the effect of different food and liquid intake on plasma hyaluronan and to address mechanisms.

DESIGN

The effects on plasma hyaluronan of ingestion of high-fat and low-fat meals, glucose solution, and saline, and of intravenous metoclopramide and oral cisapride were defined in healthy fasted subjects by serial measurements over 5 h. Hyaluronan was measured by a radiometric assay.

RESULTS

After test meals and glucose ingestion, plasma hyaluronan rose to 1.7-13 times the fasting levels in 11 healthy volunteers. Peak values were observed in most subjects 45-90 min after ingestion and reached levels in six subjects that might suggest the presence of hepatic fibrosis or cirrhosis. No change occurred after ingestion of 0.48 L iso-osmotic NaCl solution, equal in bulk to the glucose solution. Stimulation of gastrointestinal motility with metoclopramide had no effect but oral cisapride induced a pattern of elevated plasma hyaluronan which mimicked that induced by foodstuffs.

CONCLUSIONS

Displacement of hyaluronan from gastrointestinal tissues prevails over the increased clearance expected from elevated portal blood flow. The heightened flux of tissue fluid necessary to displace tissue hyaluronan is best explained by vasodilatation in response to ingestion of nutrients, and subsequent increase in intestinal lymph flow, rather than by fluid absorption, together with gut contraction. The discriminating value of plasma hyaluronan in clinical practice may be greatly enhanced by sampling in fasted subjects at rest.

Emerging drugs for gastro-oesophageal reflux disease

Gastro-oesophageal reflux disease is a common medical problem caused by the exposure of the distal oesophagus to gastric contents. Existing medical therapy is very effective, but symptomatic relief with acid suppressants is often delayed. Treatment focuses on the suppression of gastric acid rather than on the underlying pathophysiological abnormalities, such as transient non-swallow-related lower oesophageal sphincter relaxation. Current pharmacological developments concentrate on drugs with lasting acid suppression and a faster onset of action. Compounds interacting with the complex neuromuscular regulation of the gastro-oesophageal junction are also being developed and offer exciting prospects.

Inhibition of L-type Ca(2+) current in Guinea pig ventricular myocytes by cisapride

The effect of cisapride on L-type Ca(2+) current (I(Ca,L)) was studied in guinea pig ventricular myocytes using a whole-cell voltage-clamp technique and a conventional action potential recording method. Myocytes were held at -40 mV, and internally dialyzed and externally perfused with Na(+)- and K(+)-free solutions; cisapride elicited a concentration-dependent block of peak I(Ca,L), with a half-maximum inhibition concentration (IC(50)) of 46.9 microM. There was no shift in the reversal potential, nor any change in the shape of the current-voltage relationship of I(Ca,L) in the presence of cisapride. Inhibition of cisapride was not associated with its binding to serotonin or to alpha-adrenergic receptors because ketanserin, SB203186, and prazosin had no effect on the inhibitory action of cisapride on I(Ca,L). Cisapride elicited a tonic block and a use-dependent block of I(Ca,L). These blocking effects were voltage dependent as the degree of inhibition at -40 mV was greater than that at -70 mV. Cisapride shifted the steady-state inactivation curve of I(Ca,L) in the negative direction, but had no effect on the steady-state activation curve. Cisapride also delayed the kinetics of recovery of I(Ca,L) from inactivation. At a slow stimulation frequency (0.1 Hz), the action potential duration in guinea pig papillary muscles showed biphasic effects; it was prolonged by lower concentrations of cisapride, but shortened by higher concentrations. These findings suggest that cisapride preferentially binds to the inactivated state of L-type Ca(2+) channels. The inhibitory effect of cisapride on I(Ca,L) might play an important role in its cardiotoxicity under pathophysiological conditions, such as myocardial ischemia.

Noninvasive Assessment of Gastric Emptying by Near-Infrared Fluorescence Reflectance Imaging in Mice: Pharmacological Validation with Tegaserod, Cisapride, and Clonidine

Noninvasive near-infrared fluorescence reflectance imaging (FRI) is an in vivo technique to assess physiological and molecular processes in the intact organism. Here we describe a method to assess gastric emptying in mice. TentaGel beads with covalently bound cyanine dye (Cy5.5) conjugates as fluorescent probe were administered by oral gavage. The amount of intragastric beads/label was derived from the fluorescence signal intensity measured in a region of interest corresponding to the mouse stomach. The FRI signal intensity decreased as a function of time reflecting gastric emptying. In control mice, the gastric half-emptying time was in agreement with literature data. Pharmacological modulation of gastric motility allowed the evaluation of the sensitivity of the FRI-based method. Gastric emptying was either stimulated or inhibited by treatment with the 5-HT(4) receptor agonists tegaserod (Zelnorm) and cisapride or the alpha(2)-receptor agonist clonidine, respectively. Tegaserod and cisapride dose-dependently accelerated gastric emptying. In contrast, clonidine dose-dependently delayed gastric emptying. In conclusion, FRI using fluorescently labeled beads allows the reliable determination of gastric emptying as well as the assessment of pharmacological interventions. The technique thus offers the potential to characterize molecular targets and pathways involved in physiological regulation and pharmacological modulation of gastric emptying.

Determination of cisapride, its oxidation product, propyl and butyl parabens in pharmaceutical dosage form by reversed-phase liquid chromatography

A simple, rapid and reproducible high-performance liquid chromatography (HPLC) assay for cisapride, its oxidation product (OP), propyl and butyl parabens in a pharmaceutical formulation is described. Chromatography was performed at room temperature by pumping acetonitrile-20 mM phosphate buffer pH 7 (50:50, v/v) at 1.5 ml min(-1) through C8 reversed-phase column. Cisapride, OP, propyl and butyl parabens were detected at 276 nm and were eluted at 9.7, 3.1, 5.1 and 7.1 min, respectively. Calibration plots were linear (r>0.999) for all compounds from 0.5 to 200 microg ml(-1) for cisapride and OP and 0.1-200 microg ml(-1) for propyl and butyl parabens. Detection limits for cisapride, OP, propyl and butyl parabens were 40, 46, 48 and 54 ng ml(-1), respectively. Forced degradation investigations showed that cisapride does not undergo degradation under heat, acidic and basic conditions but it was susceptible to oxidation. The proposed method was successfully applied to the assay of cisapride in the presence of preservatives and OP in a commercial suspension.

Oral erythromycin and the risk of sudden death from cardiac causes

BACKGROUND

Oral erythromycin prolongs cardiac repolarization and is associated with case reports of torsades de pointes. Because erythromycin is extensively metabolized by cytochrome P-450 3A (CYP3A) isozymes, commonly used medications that inhibit the effects of CYP3A may increase plasma erythromycin concentrations, thereby increasing the risk of ventricular arrhythmias and sudden death. We studied the association between the use of erythromycin and the risk of sudden death from cardiac causes and whether this risk was increased with the concurrent use of strong inhibitors of CYP3A.

METHODS

We studied a previously identified Tennessee Medicaid cohort that included 1,249,943 person-years of follow-up and 1476 cases of confirmed sudden death from cardiac causes. The CYP3A inhibitors used in the study were nitroimidazole antifungal agents, diltiazem, verapamil, and troleandomycin; each doubles, at least, the area under the time-concentration curve for a CYP3A substrate. Amoxicillin, an antimicrobial agent with similar indications but which does not prolong cardiac repolarization, and former use of erythromycin also were studied, to assess possible confounding by indication.

RESULTS

The multivariate adjusted rate of sudden death from cardiac causes among patients currently using erythromycin was twice as high (incidence-rate ratio, 2.01; 95 percent confidence interval, 1.08 to 3.75; P=0.03) as that among those who had not used any of the study antibiotic medications. There was no significant increase in the risk of sudden death among former users of erythromycin (incidence-rate ratio, 0.89; 95 percent confidence interval, 0.72 to 1.09; P=0.26) or among those who were currently using amoxicillin (incidence-rate ratio, 1.18; 95 percent confidence interval, 0.59 to 2.36; P=0.65). The adjusted rate of sudden death from cardiac causes was five times as high (incidence-rate ratio, 5.35; 95 percent confidence interval, 1.72 to 16.64; P=0.004) among those who concurrently used CYP3A inhibitors and erythromycin as that among those who had used neither CYP3A inhibitors nor any of the study antibiotic medications. In contrast, there was no increase in the risk of sudden death among those who concurrently used amoxicillin and CYP3A inhibitors or those currently using any of the study antibiotic medications who had formerly used CYP3A inhibitors.

CONCLUSIONS

The concurrent use of erythromycin and strong inhibitors of CYP3A should be avoided.

Functional dyspepsia: drugs for new (and old) therapeutic targets

The therapeutic management of functional dyspepsia remains a major challenge for the gastroenterologist. Current therapies available are based on putative underlying pathophysiologic mechanisms, including gastric acid sensitivity, slow gastric emptying and Helicobacter pylori infection, but only a small proportion of patients achieve symptomatic benefit from these therapeutic approaches. Relatively novel mechanistic concepts under testing include impaired gastric accomodation, visceral hypersensitivity, and central nervous system dysfunction. Serotonergic modulators (e.g. the 5-HT4 agonist tegaserod, the 5-HT3 antagonist alosetron and the 5-HT1P agonist sumatriptan), CCK-1 antagonists (e.g. dexloxiglumide), opioid agonists (e.g. asimadoline), N-methyl-D-aspartate (NMDA) receptor antagonists (e.g dextromethorphan), neurokinin antagonists (e.g. talnetant), capsaicin-like agents and antidepressants are among the agents currently under investigation. It seems unlikely, however, that targeting a single mechanism with an individual drug will result in complete symptom remission in most cases.

Gastric motility disorders: management that optimizes nutritional status

Gastric motility disorders are relatively common, and treatment is often challenging. Various etiologies account for numerous clinical sequelae, with weight loss and severe protein-calorie malnutrition often seen in advanced stages of these disorders. In addition to gastrointestinal motor function, an appreciation of visceral sensation is essential to better understand the symptoms found in these patients, as well as possible therapeutic alternatives. This article provides an overview of gut motor and sensory function, techniques available for diagnosing motor disorders, and the principles of nutritional and medical management. Specific nutritional recommendations and a review of pharmacologic agents and novel treatment modalities are provided.

Serotonin-induced potentiation of cholinergic responses to electrical field stimulation in normal and neurogenic overactive human detrusor muscle

OBJECTIVE

To compare the serotonin (5-HT)4-receptor-mediated effects of 5-HT on the potentiation of cholinergic responses to electrical-field stimulation (EFS) in isolated strips of detrusor muscle from patients with normal or neurogenic overactive bladders.

MATERIAL AND METHODS

Strips of detrusor muscle were field-stimulated (10 Hz, 0.01 ms duration, 60 V for 5 s) at 100-s intervals until consistent responses were obtained. In the presence of methiothepin, ketanserin and ondansetron (all 1 mumol/L) to block 5-HT1, 5-HT2 and 5-HT3 receptors, respectively, the cumulative administration of 5-HT or the selective 5-HT4 agonist cisapride, produced concentration-dependent enhancement of responses to EFS in both types of tissue.

RESULTS

The maximum potentiation induced by 5-HT in neurogenic overactive detrusor muscle was reduced (P < 0.05) by about half compared to normal detrusor muscle, but EC50 values obtained in normal and overactive tissue were not significantly different. Cisapride was less potent than 5-HT and acted as a partial agonist relative to 5-HT. The selective 5-HT4 receptor antagonist RS-100235 was a potent antagonist of the 5-HT-induced potentiation of responses to EFS. At 3 nmol/L RS-100235 antagonized the effects of 5-HT in both groups of tissues without affecting the maximum responses. The affinity estimates (apparent pKB values of 9.2-9.5) for this antagonist were similar in normal and overactive detrusor muscle.

CONCLUSIONS

These results indicate that 5-HT4 receptor-mediated potentiation of field-stimulated responses is lower in the neurogenic overactive detrusor muscle than in normal tissue. 5-HT4 receptor antagonist affinity is unchanged in the neurogenic overactive bladder.

Modifiers of gastrointestinal motility of cattle

Little clinically relevant, evidence-based data about the effect of motility modifiers on the GI tract of cattle are currently available. Additionally, some of the published results seem to be contradictory. Three main facts explain this apparent discrepancy: (1) Results may not be transferred from one species to another, because presence, concentration, location, distribution, and function of specific receptors may differ significantly among species. (2) The lack of a significant effect on smooth muscle preparations in vitro does not necessarily exclude a certain drug's motility-modifying property on affected animals in vivo. Certain drugs bind to receptors outside the myenteric plexus. Others, such as lidocaine and adrenergic-, dopaminergic-, and opioid-antagonists increase only GI motility, if inhibitory reflexes or a hyperactive state of the inhibitory sympathetic nervous system preexists. (3) Effects of motility modifiers as found in healthy experimental animals in vivo may not be similar to those found in spontaneously diseased animals. Accurate and reliable data on the effect of modifiers of GI motility of cattle will be obtained only from double-blinded, evidence-based, in vivo studies on spontaneously affected animals. Because well-documented results from such studies are extremely rare, intensive research in this field is warranted in the future.

Diagnosis and treatment of neuromuscular disorders of the stomach

Gastric neuromuscular disorders encompass a spectrum of dysfunction in nerve and smooth muscle that includes gastric visceral hypersensitivity, gastric dysrhythmias, fundic dysfunction, antral hypomotility, and gastroparesis. Patients with each disorder may present with such vague dyspepsia symptoms as early satiety, upper abdominal discomfort, bloating, or nausea with or without vomiting. A careful history and physical examination may suggest a gastric neuromuscular disorder, but symptoms are nonspecific. Gastroparesis is the most severe form of neuromuscular dysfunction. Such reversible causes of gastroparesis as mechanical obstruction of the stomach and chronic mesenteric ischemia must be excluded. Gastroparesis, gastric dysrhythmias, and hypersensitivity may follow viral infection or be due to degenerative processes that affect the gastric enteric neurons, smooth muscle, or interstitial cells of Cajal. Commonly, the cause of these gastric neuromuscular disorders is unknown. An approach to the diagnosis and treatment of gastric neuromuscular disorders is reviewed, including dietary counseling, drugs, and medical devices.

Electrocardiographic and hemodynamic effects of cisapride alone and combined with erythromycin in anesthetized dogs

The cardiovascular effects of cisapride administered intravenously at escalating doses with and without pretreatment with erythromycin were evaluated in morphine/chloralose anesthetized dogs. Dogs were instrumented to permit simultaneous recording of ECGs, left ventricular (LVP) and aortic (AoP) pressures, as well as programmed electrical stimulation (PES). Escalating intravenous doses of cisapride from 2 to 8 mg/kg (four times the recommended therapeutic dose) increased the heart rate (HR) and prolonged the corrected QT interval (QTc) (p < 0.05) compared to controls. Pretreatment with erythromycin failed to enhance the effect of cisapride on either HR or QTc. Cisapride with or without erythromycin pretreatment had no effect on AoP, but depressed indices of left ventricular contractility (dP/dt(max) decreased while PEP/ET increased) compared to controls. No dogs developed spontaneous arrhythmias, and arrhythmias were not inducible by PES. Cisapride with or without erythromycin pretreatment altered the orientation of the T-wave vector (p < 0.05) compared to controls, indicating a primary effect of cisapride on ventricular repolarization. The QTc and T wave changes observed were consistent with the known action of cisapride on canine I(Kr) channels.

5-HT4 receptors contribute to the motor stimulating effect of levosulpiride in the guinea-pig gastrointestinal tract

BACKGROUND

The dopamine D2 receptor antagonist levosulpiride is a substituted benzamide derivative, whose gastrokinetic properties are exploited clinically for the management of functional dyspepsia. However, for other benzamide derivatives, such as cisapride and mosapride, agonism towards serotonin 5-HT4 receptors is considered the main mechanism leading to gastrointestinal prokinesia.

AIMS

To assess whether levosulpiride is able to activate 5-HT4 receptors in the guinea-pig isolated gastrointestinal tract.

MATERIALS AND METHODS

Circular muscle strips from gastric antrum, and colonic longitudinal muscle strips were used to detect electrically stimulated neurogenic contractions. The effect of levosulpiride was assessed in the absence and presence of GR125487, a selective 5-HT4 receptor antagonist. Furthermore, potential interaction of levosulpiride with 5-HT3 receptors and tissue cholinesterases was assessed in unstimulated ileal longitudinal muscle-myenteric plexus preparations.

RESULTS

Antral and colonic strip contractions were cholinergic/tachykinergic in nature. Micromolar concentrations of levosulpiride potentiated submaximal responses, through a mechanism competitively antagonized by GR125487 (pKB=9.4). In LMMPs, levosulpiride slightly affected contractions caused by the 5-HT, receptor agonist 2-methyl-5-HT, and had no effect on contractions to exogenous acetylcholine.

CONCLUSIONS

Our results indicate that levosulpiride acts as a moderate agonist at the 5-HT4 receptor. This property, together with antagonism at D2 receptors, may contribute to its gastrointestinal prokinetic effect.

Age-related differences in the direct cardiac effects of cisapride: narrower safety range in the hearts of young rabbits

Although cisapride is widely used to treat gastrointestinal motility disorders, it has been associated with QT prolongation, torsades de pointes, and cardiac arrest. Only in children, however, has atrioventricular (AV) block after cisapride been reported. This study used Langendorff perfusion to determine the direct effects of cisapride (0.03, 0.1, 0.3, and 1 microM) on the conduction properties of neonatal (<7 d) and adult (>3 mo) rabbit hearts. At a clinically relevant dose (0.03 microM), cisapride slowed the recovery of the His-Purkinje system. At 0.1 microM, the refractoriness of the His-Purkinje system and conduction through this system were prolonged. Corrected QT intervals and the ventricular refractory period were also lengthened. These parameters were significantly more prolonged in neonates than in adults. The level of AV block at rapid atrial pacing shifted from the AV node to the His-Purkinje system, with an ED(50) of 0.06 and 0.52 microM in the neonate and the adult, respectively. In the neonate, cisapride even resulted in infranodal AV block rhythm (ED50 = 0.12 microM), but this was not the case in the adult. Polymorphic ventricular tachycardia after cisapride was induced in one in seven neonates (14%;, 0.1 microM) and in one in seven adults (14%; 0.03 microM). It is concluded that cisapride may affect the refractoriness of cardiac tissue and that the His-Purkinje system seems to be the most sensitive. In neonatal hearts, this modification may, in fact, progress to infranodal AV block. Such susceptibility to cisapride strongly indicates that the therapeutic safety range used for the young heart should be narrowed.