The effect of rabeprazole on regional gastric acidity and the postprandial cardia/gastro-oesophageal junction acid layer in normal subjects: a randomized, double-blind, placebo-controlled study

Use of Gastrointestinal Simulator, Mass Transport Analysis, and Absorption Simulation to Investigate the Impact of pH Modifiers in Mitigating Weakly Basic Drugs' Performance Issues Related to Gastric pH: Palbociclib Case Study

It is well known that reduced gastric acidity, for example with concomitant administration of acid reducing agents, can result in variable pharmacokinetics and decreased absorption of weakly basic drugs. It is important to identify the risk of reduced and variable absorption early in development, so that product design options to address the risk can be considered. This article describes the utilization of in vitro and in silico tools to predict the effect of gastric pH, as well as the impact of adding pH modifiers, in mitigating the effect of acid reducing agents on weak base drugs' dissolution and absorption. Palbociclib, a weakly basic drug, was evaluated in low and high gastric pH conditions in a multicompartmental dissolution apparatus referred to as a gastrointestinal simulator (GIS). The GIS permits the testing of pharmaceutical products in a way that better assesses dissolution under physiologically relevant conditions of pH, buffer concentration, formulation additives, and physiological variations including GI pH, buffer concentrations, secretions, stomach emptying rate, residence time in the GI, and aqueous luminal volume. To predict drug dissolution in the GIS, a hierarchical mass transport model was used and validated using in vitro experimental data. Dissolution results were then compared to observed human clinical plasma data with and without proton pump inhibitors using a GastroPlus absorption model to predict palbociclib plasma profiles and pharmacokinetic parameters. The results showed that the in silico model successfully predicted palbociclib dissolution in the GIS under low and high gastric pH conditions with and without pH modifiers. Furthermore, the GIS data coupled with the in silico tools anticipated (1) the reduced palbociclib exposure due to proton pump inhibitor coadministration and (2) the mitigating effect of a pH-modifying agent. This study provides tools to help in the development of orally administered formulations to overcome the effect of elevated gastric pH, especially when formulating with pH modifiers.

Consensus statements and recommendations on the management of mild-to-moderate gastroesophageal reflux disease in the Southeast Asian region

This paper reports the proceedings from the first consensus meeting on the management of mild-to-moderate gastroesophageal reflux disease (GERD) in the Southeast Asian (SEA) region. Seventeen statements were drawn up by a steering committee that focused on epidemiology, mechanism of action, diagnostic investigations, and treatment. Voting on the recommendations used the Delphi method with two rounds of voting among the 10 panel members. The consensus panel agreed that GERD is mostly a mild disease in the SEA region with predominantly non-erosive reflux disease (NERD). Complicated GERD and Barrett's esophagus are infrequently seen. The panel recommended endoscopy in patients with alarm or refractory symptoms but cautioned that the incidence of gastric cancer is higher in SEA. pH and impedance measurements were not recommended for routine assessment. The acid pocket is recognized as an important pathogenic factor in GERD. Lifestyle measures such as weight reduction, avoidance of smoking, reduction of alcohol intake, and elevation of the head of the bed were recommended but strict avoidance of specific foods or drinks was not. Alginates was recommended as the first-line treatment for patients with mild-to-moderate GERD while recognizing that proton-pump inhibitors (PPIs) remained the mainstay of treatment of GERD. The use of alginates was also recommended as adjunctive therapy when GERD symptoms were only partially responsive to PPIs.

Evaluations of Gastric Acid Pocket Using Novel Vertical 8-Channel pH Monitoring System and Effects of Acid Secretion Inhibitors

Background/Aims

The gastric acid pocket has an important role in gastroesophageal reflux disease development. In this study, we utilized a novel 8-channel pH monitoring system with sensor intervals of 1 cm on the vertical axis for evaluation of postprandial gastric acid pocket in healthy Japanese adults, as well as the effects of vonoprazan and rabeprazole.

Methods

Twelve healthy volunteers without Helicobacter pylori infection were enrolled. A catheter was inserted transnasally and positioned under X-ray guidance, then postprandial acid pocket formation was monitored over time in a sitting position. Thereafter, acid pocket changes were assessed following administration of vonoprazan (20 mg) or rabeprazole (20 mg).

Results

The gastric acid pocket was successfully measured by use of the present system in 10 cases, while failure occurred in 2 because of inappropriate catheter positioning. Observed acid pockets were visualized with a mean length of 2.2 ± 0.4 channels on the top layer of food contents approximately 20 minutes after finishing a meal. There were some variations for lasting time of the acid pocket. Complete elimination within 3 hours after administration of vonoprazan was noted in all cases. Likewise, following administration of rabeprazole, the acid pocket was eliminated in 7 cases, while acidity was reduced though the pocket remained observable in 3.

Conclusions

Gastric acid pocket observations were possible using our novel vertical 8-channel sensor catheter. The present findings showed that vonoprazan strongly suppressed acid secretion within a short period, suggesting its effectiveness for gastroesophageal reflux disease treatment.

Comparative evaluation for thermostability and gastrointestinal survival of probiotic Bacillus coagulans MTCC 5856

Thermal stability (D-value and pasteurization) and gastric acid resistance of spore forming and nonspore forming probiotic strains were evaluated in this study. Bacillus coagulans MTCC 5856 spores showed highest thermal resistance (D-value 35.71 at 90 °C) when compared with other Bacillus strains and Lactobacillus species. B. coagulans strains exhibited significantly higher resistance to simulated gastric juice (pH 1.3, 1.5, and 2.0) compared to Lactobacillus strains. It also showed high resistance to cooking conditions of chapati (whole wheat flour-based flatbread) (88.94% viability) and wheat noodles (and 94.56% viability), suggesting remarkable thermal resistance during food processing. Furthermore, B. coagulans MTCC 5856 retained 73% viability after microwave cooking conditions (300 s, at 260 °C) and 98.52% in milk and juice at pasteurization temperature (420 min, at 72 °C). Thus, B. coagulans MTCC 5856 clearly demonstrated excellent resistance to gastric acid and high temperature (90 °C), thereby suggesting its extended application in functional foods (milk, fruit juices, chapati, and wheat noodles) wherein high temperature processing is involved.

pH-dependent ileocolonic drug delivery, part II: preclinical evaluation of novel drugs and novel excipients

Novel drugs and novel excipients in pH-dependent ileocolonic drug delivery systems have to be tested in animals. Which animal species are suitable and what in vivo methods are used to verify ileocolonic drug delivery?

pH-dependent ileocolonic drug delivery, part I: in vitro and clinical evaluation of novel systems

After the pH dependency of novel pH-dependent ileocolonic drug delivery systems is confirmed in vitro, their performance should be evaluated in human volunteers.

24-hour multi-pH recording of the postprandial acid pocket and the nocturnal acid distribution at the esophagogastric junction in healthy volunteers

BACKGROUND

Postprandial stationary pH monitoring studies have identified the acid pocket. To what extent a similar pool of acid is present in the fasting state or at night remains however unclear.

METHODS

The study was performed in 9 HV without a hiatal hernia. A pH-impedance-pressure catheter was positioned at the Z-line. First, the presence of the acid pocket was monitored under stationary conditions during 2 hours after ingestion of a standardized meal. Thereafter, the equipment was connected to an ambulatory monitoring device for 24-hour recording.

RESULTS

Under stationary conditions, a postprandial acid pocket was present in 7 of the 9 HV, from 9 ± 7 minutes after meal onwards during 47 ± 8 minutes. During ambulatory 24-hour monitoring, postprandial acid pockets emerged significantly later, but no differences in duration or position were detected. During nighttime, an acid pool was detected with its proximal border at the level of the cardia, which at later, time points gradually moved to a more distal position. This led to a gradual decrease in nocturnal acid exposure from proximal to distal, a phenomenon that was preceded by a bust of gastric contractions. Nocturnal reflux originated from the cardiac region, and was more acidic in the early compared with late nocturnal period.

CONCLUSION

The acid pocket is present in the postprandial period under both stationary and ambulatory conditions. Of interest, at night, a pool of acid can be demonstrated which is periodically shifted more distally. This pool of acid represents the reservoir from which nocturnal reflux originates.

The Characteristics of Postprandial Proximal Gastric Acid Pocket in Gastroesophageal Reflux Disease

Background

Postprandial proximal gastric acid pocket (PPGAP) plays important roles in gastroesophageal reflux disease (GERD). In this study, we analyzed the characteristics of PPGAP in GERD.

Material/Methods

There were 17 normal participants and 20 GERD patients who completed a gastroesophageal reflux disease questionnaire (GerdQ) and underwent a gastroscopy, a high-resolution manometry, an esophageal 24-hour pH monitoring, and a station pull-through pH monitoring to assess their symptomatic degree, endoscopic change, acid exposure, and PPGAP.

Results

PPGAP was present in all participants. Compared with normal participants, the PPGAP in GERD patients was significantly different, thus the disappearing time was significantly later (p<0.001), the lasting time was significantly longer (p<0.001), the length was significantly longer (p<0.001), and the lowest pH and the mean pH were significantly lower (p<0.001). The length of PPGAP in GERD patients was positively correlated with GerdQ score (p<0.05). The disappearing time, the lasting time, and the length of PPGAP in GERD patients was positively correlated with the DeMeester score (p<0.01). The lowest pH and the mean pH of PPGAP in GERD patients was negatively correlated with the DeMeester score (p<0.001).

Conclusions

PPGAP was generally present. PPGAP in GERD patients had characteristics of long time period, long length, and high acidity. Its length was positively correlated with subjective symptomatic degree. Its period, length, and acidity were positively correlated with the objective acid exposure. PPGAP seems to be the originator of acid reflux events and plays important roles in GERD.

Randomised clinical trial: alginate (Gaviscon Advance) vs. placebo as add-on therapy in reflux patients with inadequate response to a once daily proton pump inhibitor

BACKGROUND

Many reflux patients remain symptomatic on a standard dose of proton pump inhibitor (PPI). Alginates decrease the number of reflux events by forming a raft on top of the stomach content and thus offer a supplemental mechanism of action to acid suppression.

AIM

To assess the efficacy of an alginate (Gaviscon Advance, Reckitt Benckiser, Slough, UK) on reflux symptoms in patients with persistent symptoms despite once daily PPI.

METHODS

This was a multicentre, randomised, placebo-controlled, 7-day double-blind trial preceded by a 7-day run-in period. Reflux symptoms were assessed using the Heartburn Reflux Dyspepsia Questionnaire (HRDQ). Based on symptom score during run-in, eligible patients were randomised to Gaviscon Advance 10 mL four times a day or placebo in addition to a once daily PPI. The primary endpoint was change in HRDQ score post-treatment compared to baseline.

RESULTS

One hundred and thirty-six patients were randomised. Change in HRDQ reflux score was significantly greater for Gaviscon Advance (mean: -5.0, s.d.: 4.7) than for placebo (mean: -3.5, s.d.: 5.5) with an LS mean difference of 1.6 [95% CI -3.1 to -0.1], P = 0.03. A decrease in the mean (s.d.) number of nights with symptoms was observed from 3.6 (2.8) to 3.0 (3.0) in the placebo group and from 3.9 (2.8) to 2.2 (2.7) for the Gaviscon Advance group. This reduction was significantly greater in the Gaviscon Advance group than in the placebo group [LS mean difference = -0.9, 95% CI (-1.6 to -0.2), P < 0.01].

CONCLUSION

In patients with residual reflux symptoms despite PPI treatment, adding an alginate offers additional decrease in the burden of reflux symptoms (EudraCT/IND Number: 2011-005486-21).

The Role of the Acid Pocket in Gastroesophageal Reflux Disease

Gastroesophageal reflux disease is one of the commonest chronic conditions in the western world and its prevalence is increasing worldwide. The discovery of the acid pocket explained the paradox of acid reflux occurring more frequently in the postprandial period despite intragastric acidity being low due to the buffering effect of the meal. The acid pocket was first described in 2001 when it was detected as an area of low pH immediately distal to the cardia using dual pH electrode pull-through studies 15 minutes after a meal. It was hypothesized that there was a local pocket of acid close to the gastroesophageal junction that escapes the buffering effect of the meal, and that this is the source of postprandial acidic reflux. The presence of the acid pocket has been confirmed in other studies using different techniques including high-resolution pHmetry, Bravo capsule, magnetic resonance imaging, and scintigraphy. This review aims to describe what we know about the acid pocket including its length, volume, fluid constituents, and its relationship to the lower esophageal sphincter and squamocolumnar junction. We will discuss the possible mechanisms that lead to the formation of the acid pocket and examine what differences exist in patients who suffer from acid reflux. Treatments for reflux disease that affect the acid pocket will also be discussed.

Volume, distribution and acidity of gastric secretion on and off proton pump inhibitor treatment: a randomized double-blind controlled study in patients with gastro-esophageal reflux disease (GERD) and healthy subjects

Background

Postprandial accumulation of gastric secretions in the proximal stomach above the meal adjacent to the esophagogastric junction (EGJ), referred to as the ‘acid pocket’, has been proposed as a pathophysiological factor in gastro-esophageal reflux disease (GERD) and as a target for GERD treatment. This study assessed the effect of proton pump inhibitor (PPI) therapy on the volume, distribution and acidity of gastric secretions in GERD and healthy subjects (HS).

Methods

A randomized, double blind, cross-over study in 12 HS and 12 GERD patients pre-treated with 40 mg pantoprazole (PPI) or placebo b.i.d. was performed. Postprandial secretion volume (SV), formation of a secretion layer and contact between the layer and the EGJ were quantified by Magnetic Resonance Imaging (MRI). Multi-channel pH-monitoring assessed intragastric pH.

Results

A distinct layer of undiluted acid secretion was present on top of gastric contents in almost all participants on and off high-dose acid suppression. PPI reduced SV (193 ml to 100 ml, in HS, 227 ml to 94 ml in GERD; p < 0.01) and thickness of the acid layer (26 mm to 7 mm, 36 mm to 9 mm respectively, p < 0.01). No differences in secretion volume or layer thickness were observed between groups; however, off treatment, contact time between the secretion layer and EGJ was 2.6 times longer in GERD compared to HS (p = 0.012). This was not the case on PPI.

Conclusions

MRI can visualize and quantify the volume and distribution dynamics of gastric secretions that form a layer in the proximal stomach after ingestion of a liquid meal. The secretion volume and the secretion layer on top of gastric contents is similar in GERD patients and HS; however contact between the layer of undiluted secretion and the EGJ is prolonged in patients. High dose PPI reduced secretion volume by about 50 % and reduced contact time between secretion and EGJ towards normal levels.

Trial registration

NCT01212614.

Electronic supplementary material

The online version of this article (doi:10.1186/s12876-015-0343-x) contains supplementary material, which is available to authorized users.

Effect of baclofen on the acid pocket at the gastroesophageal junction

Previous studies established that a pocket of highly acidic gastric juice is present postprandially at the gastroesophageal junction in man. The GABA-B agonist baclofen inhibits postprandial reflux events through its effects on the lower esophageal sphincter (LES). The aim of the current study was to investigate whether baclofen would affect the location and the extent of the postprandial acid pocket in healthy volunteers. Twelve healthy volunteers underwent acid pocket studies on two different occasions, at least 1 week apart. LES position was determined preprandially with pull-through manometry. Dual pH electrode and manometry probe stepwise pull-through (1 cm/minute, LES-10 to +5 cm) was performed at 30-minute intervals for 150 minutes, with administration of placebo or baclofen 40 mg after the first and ingestion of a liquid meal after the second pull-through. After placebo, a significant drop in intragastric gastric pH was present at the gastroesophageal junction after the meal, reflecting the acid pocket, and this was associated with a drop in LES pressure. Baclofen did not affect the presence of the acid pocket, but prevented the postprandial drop in LES pressure, and the extent of the acid pocket above the upper margin of the manometrically located LES was significantly decreased by baclofen (1.6 ± 0.7 vs. 0.3 ± 0.4 cm at 60 minutes, 2.2 ± 0.6 vs. 0.2 ± 0.6 at 90 minutes, and 1.5 ± 0.5 vs. 0.7 ± 0.7 cm at 120 minutes, all P < 0.05). Baclofen does not alter the intragastric acid pocket, but limits its extension into the distal esophagus, probably through an increase in postprandial LES pressure.

Gaviscon Double Action Liquid (antacid & alginate) is more effective than antacid in controlling post-prandial oesophageal acid exposure in GERD patients: a double-blind crossover study

BACKGROUND

Recent studies have shown that Gaviscon Double Action Liquid (a combination alginate-antacid) administered post-prandially co-localises with the acid pocket, the 'reservoir' for post-prandial acid reflux.

AIM

To compare the effectiveness of Gaviscon Double Action Liquid to an equivalent strength antacid without alginate in controlling post-prandial acid reflux in GERD patients.

METHODS

Fourteen GERD patients undertook two 3.5-h high-resolution manometry/pH-impedance studies during which they ate a standardised meal. In a double-blinded randomised crossover design they then took Gaviscon or CVS brand antacid, each with ~18 mmol/L acid neutralising capacity. The primary outcome was distal oesophageal acid exposure; secondary outcomes were number of reflux events, proximal extent of reflux, nadir pH of the refluxate, mechanism of reflux and reflux symptoms scored with a validated instrument.

RESULTS

Ten patients completed the study. Gaviscon studies had significantly less distal oesophageal acid exposure and greater nadir refluxate pH in the 30-150 min post-prandial period than antacid studies. There were no differences in the number of reflux events (acid or weakly acidic) or the number of proximal reflux events (15-17 cm above the LES) with either study medication.

CONCLUSIONS

Gaviscon Double Action Liquid is more effective than an antacid without alginate in controlling post-prandial oesophageal acid exposure. However, the number and spatial distribution of reflux events within the oesophagus are similar. This suggests that Gaviscon main effectiveness relates to its co-localisation with and displacement/neutralisation of the post-prandial acid pocket, rather than preventing reflux.

Proton pump inhibitors reduce the size and acidity of the acid pocket in the stomach

BACKGROUND & AIMS

The gastric acid pocket is believed to be the reservoir from which acid reflux events originate. Little is known about how changes in position, size, and acidity of the acid pocket contribute to the therapeutic effect of proton pump inhibitors (PPIs) in patients with gastroesophageal reflux disease (GERD).

METHODS

Thirty-six patients with GERD (18 not taking PPIs, 18 taking PPIs; 19 men; age, 55 ± 2.1 y) were analyzed by concurrent high-resolution manometry and pH-impedance monitoring after a standardized meal. The acid pocket was visualized using scintigraphy after intravenous administration of (99m)technetium-pertechnetate. The size of the acid pocket was measured and its position was determined, relative to the diaphragm, using radionuclide markers on a high-resolution manometry catheter. At the end of the study, the acid pocket was aspirated, and its pH level was measured.

RESULTS

The number of reflux episodes was comparable between patients on and off PPIs, but the number of acid reflux episodes was reduced significantly in patients on PPIs. In patients on PPIs, the acid pocket was smaller and more frequently located below the diaphragm. The mean pH of the acid pocket was significantly lower in patients not taking PPIs (n = 6) than in those who were (n = 16) (0.9; range, 0.7-1.2 vs 4.0; range, 1.6-5.9; P < .001). The pH of acid pockets correlated significantly with the lowest pH values measured for refluxate (r = 0.72; P < .01).

CONCLUSIONS

Based on analyses of acid pockets in patients with GERD, the acid pocket appears to be a reservoir from which reflux occurs when patients are receiving PPIs. PPIs might affect the size, acidity, or position of the acid pocket, which contributes to the efficacy in patients with GERD.

The postprandial acid pocket does not extend into most distal esophagus: evidence from pH studies performed immediately above the squamocolumnar junction

OBJECTIVE

The postprandial acid pocket is suggested to be an important factor in the pathogenesis of gastroesophageal reflux disease (GERD) as it according to the theory extends into the distal esophagus. The aim of this study was to test the hypothesis that the acid pocket transverses the squamocolumnar junction (SCJ) and exposes the most distal esophagus to gastric acid for extended periods following a meal.

MATERIAL AND METHODS

Fifty asymptomatic volunteers and 75 patients with GERD underwent 48-h pH monitoring with the electrode of a pH capsule placed immediately above the SCJ. The characteristics of esophageal acid exposure from the 90-min postprandial periods were compared with those observed during the upright, preprandial periods.

RESULTS

In asymptomatic controls, the degree of postprandial esophageal acid exposure was similar to that observed in the preprandial periods (median % time with pH <4, 2.2 vs. 2.6, p = 0.165). In contrast, symptomatic patients had significantly greater acid exposure in the postprandial compared with the preprandial periods (median % time with pH <4, 15.5 vs. 8.5, p < 0.001). The higher degree of acid exposure during the postprandial periods was due to a significantly higher number of short reflux episodes and reflux events with long durations were infrequent.

CONCLUSION

Postprandial acid exposure in the most distal esophagus was characterized by numerous short reflux events, and reflux events of long durations were rare. Our observations suggest that the acid pocket is confined to the stomach, questioning the importance of the acid pocket in GERD.

Rabeprazole and esomeprazole in mild-to-moderate erosive gastroesophageal reflux disease: A comparative study of efficacy and safety

Objective:

To compare the efficacy and safety of rabeprazole and esomeprazole in mild-to-moderate erosive gastroesophageal reflux disease (GERD).

Materials and Methods:

A randomized, single-blinded, outdoor-based clinical study was conducted on 60 patients of mild-to-moderate erosive GERD. After baseline clinical assessment and investigations, rabeprazole (40 mg) was prescribed to 30 patients and esomeprazole (40 mg) to another 30 patients for 4 weeks. The efficacy variables were change in GERD symptom scoring, endoscopic findings, and Quality of Life in Reflux and Dyspepsia (QOLRAD) scoring over 4 weeks.

Result:

Heartburn, acid regurgitation, and overall GERD symptom scoring (P = 0.01) were significantly decreased with rabeprazole in comparison to esomeprazole. The comparative study of all five domains of the QOLARD questionnaire including overall scoring revealed a statistically significant improvement in the rabeprazole group. Endoscopic findings in the rabeprazole group showed an absolute improvement of 30% and relative improvement of 55% over esomeprazole. Both the drugs were well tolerated having no significant difference in the incidence of adverse effects.

Conclusion:

Rabeprazole (40 mg) is a better choice for mild-to-moderate GERD compared with esomeprazole (40 mg) because of its better efficacy and safety profile.

The acid pocket: a target for treatment in reflux disease?

The nadir esophageal pH of reflux observed during pH monitoring in the postprandial period is often more acidic than the concomitant intragastric pH. This paradox prompted the discovery of the "acid pocket", an area of unbuffered gastric acid that accumulates in the proximal stomach after meals and serves as the reservoir for acid reflux in healthy individuals and gastroesophageal reflux disease (GERD) patients. However, there are differentiating features between these populations in the size and position of the acid pocket, with GERD patients predisposed to upward migration of the proximal margin onto the esophageal mucosa, particularly when supine. This upward migration of acid, sometimes referred to as an "acid film", likely contributes to mucosal pathology in the region of the squamocolumnar junction. Furthermore, movement of the acid pocket itself to a supradiaphragmatic location with hiatus hernia increases the propensity for acid reflux by all conventional mechanisms. Consequently, the acid pocket is an attractive target for GERD therapy. It may be targeted in a global way with proton pump inhibitors that attenuate acid pocket development, or with alginate/antacid combinations that colocalize with the acid pocket and displace it distally, thereby demonstrating the potential for selective targeting of the acid pocket in GERD.

Postprandial proximal gastric acid pocket and gastroesophageal reflux disease

An unbuffered layer of acidity that escapes neutralization by food has been demonstrated in volunteers and gastroesophageal reflux disease patients. This postprandial proximal gastric acid pocket (PPGAP) is manometrically defined by the presence of acid reading (pH<4) in a segment of the proximal stomach between nonacid segments distally (food) and proximally (lower esophageal sphincter or distal esophagus). The PPGAP may have important clinical implications; however, it is still poorly understood. Gastric anatomy and physiology seem to be important elements for PPGAP genesis. Gastric operations and acid suppression medications may decrease distal - proximal intragastric acid reflux and help control gastroesophageal reflux.

The effects of a weakly acidic meal on gastric buffering and postprandial gastro-oesophageal reflux

BACKGROUND

Exclusion of the meal during ambulatory pH monitoring presumes that a meal completely buffers gastric acid and reflux of acidic food content cannot be distinguished from gastric acid. However, the ability of a meal to completely buffer gastric acid remains unclear.

AIM

To determine the effect of a weakly acid meal on gastric buffering and oesophageal acid exposure.

METHODS

Patients undergoing multichannel intraluminal impedance pH studies were given a standard weakly acidic meal (pH = 5.9). Gastric and oesophageal pH was measured during the meal and in 15 min intervals for 2 h postprandially.

RESULTS

The study included 30 patients, with pathological acid reflux detected in 18 patients. Complete gastric buffering occurred in seven patients (23%) and was lost in all patients within 75 min of the meal. Oesophageal acid was detected in 33% of patients within 30 min of the meal and 81% of patients during the 2 h postprandial period. Postprandial oesophageal acid exposure was greater in patients with pathological acid reflux (9 ± 2.7% vs. 1.7 ± 0.8% P = 0.05) with a trend towards more incomplete gastric acid buffering and significant differences when measuring weak acid reflux (pH 4-5). Acid reflux rarely occurred in the absence of gastric acid, with gastric acid present in 74 of 79 (94%) fifteen minute postprandial intervals with acid reflux.

CONCLUSIONS

The ability of a meal to buffer gastric acid is poor. Early postprandial oesophageal acid reflux occurs in a substantial proportion of patients. Addition of a weakly acidic or pH neutral meal to ambulatory pH monitoring may unmask early postprandial acid reflux and provide data on gastric acid buffering.

Comparative model studies of gastric toxicity of nonsteroidal anti-inflammatory drugs

A high percentage of people treated with a long-term nonsteroidal anti-inflammatory drug (NSAID) therapy suffer NSAID-induced gastrointestinal-tract-related side effects. A current hypothesis states that the side effects are related to the topical action of NSAID molecules on gastric mucus that lowers its resistance to luminal acid. The main lipids in human mucus are palmitoyloleoylphosphatidylcholine (POPC) and cholesterol (Chol). In this study, both X-ray diffraction and molecular dynamics (MD) simulation methods were employed to investigate the effects of selected NSAIDs in protonated and deprotonated states on the structural parameters of a POPC-Chol bilayer. The drugs were three commonly used NSAIDs with apparently different gastric toxicity: ketoprofen (KET), aspirin (ASP), and piroxicam (PXM). Both methods revealed that the effects of the NSAIDs on the POPC-Chol bilayer parameters were moderate and only slightly differentiated among the drugs. Much larger differences among the drugs were noticed in their interactions with interfacial water and Na(+) as well as with the polar groups of POPC and Chol, mainly via H-bonds. Of the three NSAIDs, KET interacted with POPC and water the most extensively, whereas ASP interacted with Chol and Na(+) more than did the other two. Interactions of PXM with POPC and Chol polar groups as well as with water and Na(+) were limited.

Postprandial proximal gastric acid pocket in patients after laparoscopic Nissen fundoplication

BACKGROUND

An unbuffered postprandial proximal gastric acid pocket (PPGAP) has been noticed in normal individuals and patients with gastroesophageal reflux disease (GERD). The role of gastric anatomy in the physiology of the PPGAP remains unclear. It is also unclear whether change in the PPGAP may contribute to GERD control. This study aims to analyze the presence of PPGAP in patients submitted to Nissen fundoplication.

METHODS

Fifteen patients who had a laparoscopic Nissen fundoplication (mean age = 61 years, 13 females, mean time from operation 1 year) were studied. All patients were free of foregut symptoms. Patients underwent high-resolution manometry to identify the location of the lower border of the lower esophageal sphincter (LBLES).Station pull-through pH monitoring was performed from 5 cm below the LBLES to the LBLES in increments of 1 cm in a fasting state and 10 min after a standardized fatty meal.

RESULTS

Four patterns of gastric acidity were found: (1) acid was not detected in the studied area of the stomach in 8 (53%) patients; (2) constant acidity (stomach is not alkalinized after meal), i.e., a buffered layer was not found in 3 (20%) patients; (3) PPGAP was not detected, i.e., the whole stomach is alkalinized, in 1 (7%) patient; and (4) PPGAP was noted in 3 (20%) patients with extensions of 2, 2, and 5 cm.

CONCLUSION

PPGAP is present in a minority of patients after Nissen fundoplication. This finding may explain part of the GERD control and that the gastric fundus may play a role in the genesis of the PPGAP.

Postprandial proximal gastric acid pocket and gastric pressure in patients after gastric surgery

BACKGROUND

An unbuffered postprandial proximal gastric acid pocket (PPGAP) has been demonstrated in normal individuals (NI) and patients with gastro-esophageal reflux disease (GERD). The role of gastric anatomy and gastric motility in the physiology of the PPGAP remains elusive. This study aims to analyze the correlation of PPGAP with proximal gastric pressure after gastric surgery.

METHODS

A total of 26 individuals were studied: eight patients after open Roux-en-Y gastric bypass (RYGB) for morbid obesity, six patients after laparoscopic Nissen fundoplication for GERD, seven patients after open subtotal gastrectomy for gastric cancer and five NI. Patients underwent high resolution manometry to identify the location of the lower border of the lower esophageal sphincter (LBLES) and measure gastric pressure 1, 2, 3, 4 and 5 cm below the LBLES, immediately before swallow and after the end of the LES relaxation. A station pull-through pH monitoring was performed in all but NI, from 5 cm below the LBLES to the LBLES in increments of 1 cm in a fasting state and 10 min after a standardized fatty meal.

KEY RESULTS

Our results show that: (i) proximal gastric pressures are lower after swallow compared with before swallow in NI; (ii) patients after gastric surgery tend to have higher gastric pressure before and lower after swallow compared with NI and (iii) patients after RYGB with PPGAP have an increased gastric pressure after swallows in the segment where the PPGAP is noticed.

CONCLUSIONS & INFERENCES

Gastric motility may play a role in the genesis of PPGAP in patients after RYGB. The contribution of gastric motility for the genesis of PPGAP is still elusive in other patients.

Alterations confined to the gastro-oesophageal junction: the relationship between low LOSP, TLOSRs, hiatus hernia and acid pocket

The gastro-oesophageal junction is a specialised segment of the gut designed to prevent reflux of gastric contents into the oesophagus. This task is fulfilled by two structures, i.e. the lower oesophageal sphincter and the crural diaphragm, which generate a high pressure zone. Especially during low pressure at the junction, as in case of long-lasting transient lower oesophageal sphincter relaxations, reflux can occur but mainly if a positive pressure gradient exists between stomach and the oesphagogastric junction. Although patients with gastro-oesophageal reflux disease have increased oesophageal acid exposure compared to controls, the number of transient relaxations is not increased compared to healthy controls. Instead, the risk to have acid reflux is at least doubled in patients, especially in those with a hiatal hernia, most likely as a result of the supradiaphragmatic position of the acid pocket. In hiatal hernia patients, the acid pocket is indeed often trapped in the hernia above the diaphragm. Which factors exactly determine the physical composition (liquid or gas) and the proximal extent of the refluxate however requires further research.

Postprandial proximal gastric acid pocket in patients after Roux-en-Y gastric bypass

INTRODUCTION

An unbuffered postprandial proximal gastric acid pocket (PPGAP) has been noticed in normal individuals and patients with gastroesophageal reflux disease (GERD). The role of gastric anatomy in the physiology of the PPGAP remains unclear. It is also unclear whether operations that control GERD, such as Roux-en-Y gastric bypass (RYGB) and Nissen fundoplication, change the PPGAP.

AIMS

This study aims to analyze the presence of PPGAP in patients submitted to RYGB.

METHODS

Fifteen patients who had a RYGB for morbid obesity (mean age 53 years, 14 females, mean time from operation 3 years) were studied. All patients were free of foregut symptoms. Patients underwent a high-resolution manometry to identify the location of the lower border of the lower esophageal sphincter (LBLES). A station pull-through pH monitoring was performed from 5 cm below the LBLES to the LBLES in increments of 1 cm in a fasting state and 10 min after a standardized fatty meal (40 g of chocolate, 50% fat).

RESULTS

Acidity was not detected in the stomach of four patients before meal. After meal, PPGAP was not found in eight patients. In three patients, a PPGAP was noted with an extension of 1 to 3 cm.

CONCLUSION

PPGAP is present in a minority of patients after RYGB; this finding may explain part of the GERD control after RYGB and that the gastric fundus may play a role in the genesis of the PPGAP.

Transsphincteric pH profile at the gastroesophageal junction

BACKGROUND & AIMS

Esophageal acid exposure conventionally is measured 5 cm above the lower esophageal sphincter (LES). The aim of this study was to compare pH profiles at sites within the LES, the distal esophagus, and the proximal stomach.

METHODS

Ten normal subjects underwent esophageal manometry followed by 24-hour esophagogastric pH monitoring using an 8-channel pH probe recording at 5 and 1.5 cm above and at 0, 1.5, 3.0, 4.5, 6.0, and 9.5 cm below the proximal LES border. During pH recording, a 4-hour gastric emptying test with an egg sandwich meal was performed.

RESULTS

The LES was 3.2 +/- 0.4 cm in length. There was a progressive increase in acid exposure from the esophageal to the gastric pH sensors. pH was less than 4 for 3.4% +/- 1.6%, 12.7% +/- 8.5%, 26.5% +/- 10.2%, 48.1% +/- 11.3%, 66.5% +/- 9.9%, 80.8% +/- 5.6%, 89.2% +/- 3.0%, and 96.7% +/- 1.1% of the total time for pH probes at 5 and 1.5 cm above and 0, 1.5, 3, 4.5, 6.0, and 9.5 cm below the proximal LES border, respectively. Percentage acid exposures correlated significantly with the position of the probe (r = -0.95; P < .01). Intrasphincteric acidity increased postprandially. Gastric emptying was correlated inversely with the intragastric hydrogen ion concentration (r = -0.82).

CONCLUSIONS

The percentage of recording time that pH was less than 4 was significantly higher in the intrasphincteric area and 1.5 cm above the proximal LES compared with the traditional site 5 cm above the proximal manometric LES border. High acid exposure in the intrasphincteric region might explain the susceptibility of the distal esophagus to erosions, strictures, and Barrett's esophagus.

Rapid protection of the gastroduodenal mucosa against aspirin-induced damage by rabeprazole

BACKGROUND

The ability of a proton pump inhibitor to reduce or prevent NSAID-induced gastroduodenal damage during the first 24 h has not been tested.

AIM

To determine, whether oral rabeprazole, administered 5 h before the initiation of therapeutic dosing of aspirin protects the gastroduodenal mucosa.

METHODS

Normal subjects were randomized into two groups - one received rabeprazole, 20 mg at 07:00 hours and the other placebo, before initiation of aspirin 650 mg at 12:00 hours, and then q4 h for 3 days. Upper endoscopic examinations were performed on all subjects at baseline, 24 and 72 h after initiation of aspirin. Gastroduodenal mucosal damage was scored.

RESULTS

Thirty subjects were compliant with study medications and underwent three endoscopic examinations. Salicylate concentrations were similar for the placebo and the rabeprazole groups at all times. On rabeprazole, the Lanza scores were significantly lower compared with placebo at 24 h (1.3 +/- 0.26 vs. 2.1 +/- 0.26, P < 0.05) and at 72 h (1.3 +/- 0.29 vs. 2.3 +/- 0.28, P < 0.05). Gastric antral erosion counts were less with rabeprazole than placebo at 24 (4.1 +/- 1.3 vs. 7.6 +/- 2.0, P > 0.05) and 72 h (5.3 +/- 1.8 vs. 8.0 +/- 1.5; P > 0.05).

CONCLUSIONS

Rabeprazole, initiated 5 h before the start of therapeutic dosing with aspirin, decreased Lanza scores and antral erosion counts at 24 h. These findings suggest that prophylaxis with rabeprazole could start concurrently with aspirin administration.

Pharmacokinetic and pharmacodynamic population modeling of orally administered rabeprazole in healthy Chinese volunteers by the NONMEM method

The pharmacokinetic-pharmacodynamic (PK-PD) relationship of the proton pump inhibitor rabeprazole in healthy Chinese volunteers was characterized via a population approach. Healthy Chinese male volunteers were enrolled in the clinical trial. Subjects were divided into three groups by their CYP2C19 genotype. Serum concentrations of rabeprazole were determined using high performance liquid chromatography (HPLC). The intragastric pH values were monitored simultaneously. Data analysis was performed using nonlinear mixed-effects modeling as implemented in the NONMEM software package. The final PK-PD model incorporated a one-compartment PK model with one-order absorption from the gastroenteric trace, first-order elimination pathway with one fixed-effect genotype modeling, and a full sigmoidal Emax PD model (X +/- SE: E0 = 2.30 +/- 0.189; Emax = 7.32 +/- 0.662; EC50 = 51.3 +/- 2.142 ng/ml; Hill coefficient = 5.00 +/- 0.556). The time profiles for concentration and pH value, as well as the concentration-pH value relationship of rabeprazole in healthy Chinese volunteers were well described by the developed population PK-PD model.