Experimental study of acid burden and acute oesophagitis

Influence of daily versus alternate-day dosing of vonoprazan on intragastric pH, serum gastrin, and the antiplatelet function of clopidogrel : Influence of alternate-day dosing of vonoprazan

BACKGROUND

Vonoprazan, a potassium-competitive acid blocker, inhibits gastric acid secretion and attenuates the antiplatelet function of clopidogrel more potently than esomeprazole. We investigated whether alternate-day dosing of vonoprazan might avoid this interaction with clopidogrel while providing sufficient gastric acid inhibition.

METHODS

Following 24 h of pH monitoring (control regimen), 12 healthy volunteers received three regimens (clopidogrel-only regimen: clopidogrel 75 mg daily [q.d.]; vonoprazan alternate-day regimen: vonoprazan 10 mg every other day [q.o.d.] + clopidogrel 75 mg q.d.; vonoprazan daily regimen: vonoprazan 10 mg q.d. + clopidogrel 75 mg q.d.) for 14 days in a randomized open-label crossover manner. Intragastric pH monitoring was performed for 24 h on day 13 in the clopidogrel-only and vonoprazan q.d. regimens and for 48 h on days 13 and 14 in the vonoprazan q.o.d. regimen. Serum gastrin and inhibition of platelet aggregation (IPA) were measured before the commencement of pH monitoring in each regimen.

RESULTS

Twelve volunteers completed the study. Equivalent median IPA values in the q.o.d. and q.d. regimens were measured (21.8% and 25%, respectively) and were significantly lower than that with the clopidogrel-only regimen (40.8%). The median pH4 holding time ratio for the vonoprazan q.o.d. regimen (49.7%) was superior to that of the clopidogrel-only regimen (18.4%), but was significantly inferior to that of the vonoprazan q.d. regimen (77.0%; p < 0.01).

CONCLUSION

Alternate-day administration of vonoprazan could not prevent the interaction between vonoprazan and clopidogrel, and acid inhibition was inferior to that with vonoprazan daily administration. Alternate-day administration of vonoprazan thus appears to be of questionable clinical utility.

Effect of meal timing on pharmacokinetics and pharmacodynamics of tegoprazan in healthy male volunteers

Abstract

Tegoprazan, a novel potassium‐competitive acid blocker, is used to treat acid‐related diseases. However, there is no information on the pharmacokinetic (PK) and pharmacodynamic (PD) profiles of the marketed dosage of tegoprazan under various meal timings in a fed and fasted state. The study aimed to assess the effect of meal timing on PKs and PDs of tegoprazan 50 mg after a single administration in healthy male subjects. An open‐label, single‐dose, three‐treatment, three‐period crossover study was conducted. A total of 12 subjects were orally administered a single dose of tegoprazan 50 mg among various conditions: in a fasted state, at 30 min before or 30 min after a high‐fat meal. PK parameters were estimated by the noncompartmental method. Continuous 24‐h intragastric pH monitoring was done for PD analysis. The PKs and PDs of tegoprazan were compared among the various meal timings. Compared with the fasting condition, the PK profile of tegoprazan was similar when administered 30 min before a high‐fat meal; however, delayed absorption with similar systemic exposure was observed when administered 30 min after a high‐fat meal. The magnitude of acid suppression evaluated through the PD parameters increased when administered 30 min after a high‐fat meal compared with fasting the condition and when administered 30 min before a high‐fat meal. However, the increased difference in acid suppression was not clinically significant. Meal timing had no clinically significant effect on the PKs and PDs of tegoprazan 50 mg. Therefore, the marketed dosage of tegoprazan could be administered regardless of the meal timing.

Protective and regenerative effects of a novel medical device against esophageal mucosal damage using in vitro and ex vivo models

Gastroesophageal reflux disease (GERD) is a common digestive disorder that causes esophagitis and injuries to the esophageal mucosa. GERD symptoms are recurrent during pregnancy and their treatment is focused on lifestyle changes and nonprescription medicines. The aim of this study was to characterize the mechanism of action of a new patented medical device, an oral formulation containing hyaluronic acid, rice extract, and amino acids dispersed in a bioadhesive polymer matrix, by assessing its protective effects in in vitro and ex vivo models of esophageal mucosa damage. Acidic bile salts and pepsin cocktail (BSC) added to CP-A and COLO-680 N esophagus cells were used as an in vitro GERD model to evaluate the binding capacities, anti-inflammatory effects and reparative properties of the investigational product (IP) in comparison to a viscous control. Our results showed that the IP prevents cell permeability and tight junction dysfunction induced by BSC. Furthermore, the IP was also able to down-regulate IL-6 and IL-8 mRNA expression induced by BSC stimulation and to promote tissue repair and wound healing. The results were confirmed by ex vivo experiments in excised rat esophagi through the quantification of Evans Blue permeability assay. These experiments provided evidence that the IP is able to bind to the human esophagus cells, preventing the damage caused by gastroesophageal reflux, showing potential anti-irritative, soothing, and reparative properties.

From reflux esophagitis to Barrett’s esophagus and esophageal adenocarcinoma

The occurrence of gastroesophageal reflux disease is common in the human population. Almost all cases of esophageal adenocarcinoma are derived from Barrett’s esophagus, which is a complication of esophageal adenocarcinoma precancerous lesions. Chronic exposure of the esophagus to gastroduodenal intestinal fluid is an important determinant factor in the development of Barrett’s esophagus. The replacement of normal squamous epithelium with specific columnar epithelium in the lower esophagus induced by the chronic exposure to gastroduodenal fluid could lead to intestinal metaplasia, which is closely associated with the development of esophageal adenocarcinoma. However, the exact mechanism of injury is not completely understood. Various animal models of the developmental mechanisms of disease, and theoretical and clinical effects of drug treatment have been widely used in research. Recently, animal models employed in studies on gastroesophageal reflux injury have allowed significant progress. The advantage of using animal models lies in the ability to accurately control the experimental conditions for better evaluation of results. In this article, various modeling methods are reviewed, with discussion of the major findings on the developmental mechanism of Barrett’s esophagus, which should help to develop better prevention and treatment strategies for Barrett’s esophagus.

Barrier effect of Esoxx(®) on esophageal mucosal damage: experimental study on ex-vivo swine model

The aim of the present study was to assess the potential barrier effect of Esoxx^®, a new nonprescription medication under development for the relief of gastroesophageal reflux symptoms. Esoxx is based on a mixture of hyaluronic acid and chondroitin sulfate in a bioadhesive suspension of Lutrol^® F 127 polymer (poloxamer 407) which facilitates the product adhesion on the esophageal mucosa. The mucosal damage was induced by 15 to 90 minutes of perfusion with an acidic solution (HCl, pH 1.47) with or without pepsin (2000 U/mL, acidified to pH 2; Sigma-Aldrich). Mucosal esophageal specimens were histologically evaluated and Evans blue dye solution was used to assess the permeability of the swine mucosa after the chemical injury. The results show that: (1) esophageal mucosal damage is related to the perfusion time and to the presence of pepsin, (2) mucosal damage is associated with an increased permeability, documented by an evident Evans blue staining, (3) perfusion with Esoxx is able to reduce the permeability of the injured mucosa, even after saline washing of the swine esophagus. These preliminary results support further clinical studies of Esoxx in the topical treatment of gastroesophageal reflux symptoms.

Review article: the role of bile and pepsin in the pathophysiology and treatment of gastro-oesophageal reflux disease

Gastro-oesophageal reflux disease is a multifaceted and multifactorial disorder which results from the reflux of gastric contents into the oesophagus. Animal studies suggest that synergism between acid and pepsin and conjugated bile acids have the greatest damaging potential for oesophageal mucosa, although unconjugated bile acids may be caustic at more neutral pH. Human studies are compatible with a synergistic action between acid and duodenogastric reflux in inducing lesions. During prolonged monitoring studies, typical gastro-oesophageal reflux symptoms are more related to acid reflux events than to non-acid reflux events. However, symptoms that persist during acid suppressive therapy are often related to non-acid reflux events. The therapeutic options for the non-acid component of the refluxate, including acid suppression, prokinetics, baclofen, surgery and mucosal protective agents like alginates, are discussed.

What is potent acid inhibition, and how can it be achieved?

The clinical response to antisecretory treatment correlates directly with the degree of inhibition of acid secretion achieved. Acid inhibition able to maintain the intragastric pH at a value greater than 4 for at least 16 h/day seems to heal even the most refractory acid-related diseases. It has also been shown that the degree of inhibition of acid secretion in response to antisecretory treatment depends on the genetic characteristics of the patient and on the presence of Helicobacter pylori infection. A possible definition of potent (or profound) acid inhibition is, therefore, the achievement of the aforementioned level of control of acid secretion regardless of patient characteristics or of the presence of H. pylori infection. Antisecretory drugs differ in their ability to reach potent acid inhibition. As far as the comparative efficacy of different drugs for inhibiting acid secretion is concerned, proton pump inhibitors are more efficient in inhibiting gastric acid secretion than histamine (H2) receptor antagonists. Among the different proton pump inhibitors, esomeprazole 40 mg/day exhibits greater antisecretory potency than the others at standard doses. Rabeprazole 20 mg/day and lansoprazole 30 mg/day exhibit a more rapid onset of action than omeprazole 20 mg/day or pantoprazole 40 mg/day.

Pathogenesis of reflux esophagitis and Barrett's esophagus

An understanding of the pathogenesis of reflux esophagitis and Barrett's esophagus requires knowledge of the noxious elements in gastric juice and the three major esophageal defenses designed to protect against them. When the esophageal epithelium cannot prevent gastric acid from acidifying the intercellular spaces, the foundation is set for the development of the major symptoms, signs, and complications of reflux esophagitis. Inadequate defense by the epithelium can occur by exposure to the acidic refluxate for a prolonged period of time, because of defects in the antireflux or luminal clearance mechanisms, or by exposure to ingested products that directly impair the epithelium's intrinsic defenses, rendering it vulnerable to injury from even physiologic levels of acid reflux.

Effects of Stamm Gastrostomy on Gastric Emptying Rate in Rats

AIM

Although frequency of gastroesophageal reflux (GER) increases after gastrostomy, the role of gastric emptying in GER has not been evaluated. In this study, we examined the effects of Stamm gastrostomy on gastric emptying rate in rats and whether Stamm gastrostomy induces GER or not.

METHODS

Sprague-Dawley rats were divided into three groups. Stamm gastrostomy was done in the first group (SG). Sham operation was carried out in group 2 and the 3rd group served as control. Gastric emptying was assessed using both liquid and solid meals in each group at postoperative 14th day. For solid meal emptying, after fasting of 16 h, the rats were fed for 3 h and gastric emptying rate was measured at the fifth hour. Methylcellulose was used for emptying of liquids and it was given after the animals were fasted for 16 h and gastric emptying rate was measured 30 min later. Histological evaluation for GER was performed in all groups.

RESULTS

GER was observed pathophysiologically in 5 of the 7 rats in SG group. Gastric emptying rates of liquid and solid meals were found to be similar in control, SG or sham groups.

CONCLUSION

Surgical gastrostomy does not affect the gastric emptying of solid and liquid meals in rats. Other mechanisms should be considered in the development of GER observed following gastrostomy.

The role of gastric and duodenal agents in laryngeal injury: an experimental canine model

BACKGROUND AND AIMS

The specific agents responsible for producing laryngeal signs and symptoms are currently unknown. We systematically evaluated the damaging role of gastric (acid and pepsin) and duodenal (bile acids and trypsin) ingredients individually and in combination on different laryngeal structures in an experimental canine model.

METHODS

A total of 42 beagles were studied (wt 9-15 kg each). After pentathol anesthesia all dogs underwent laryngoscopy. Injury (punch biopsy) was caused to the right vocal cord, medial arytenoid wall, and posterior cricoid wall on day 1. Pepsin (0.5 mg/ml), conjugated bile acid (CBA) (ursodeoxycholic acid, 300 micromolar), unconjugated bile acids (UBA) (cholic, 300 micromolar), trypsin (0.5 mg/ml) at pH 1-2, 4-5, and 6-7 were applied bilaterally to laryngeal sites three times per week for a total of 9-12 applications. Changes in laryngeal sites were scored visually. All dogs were sacrificed 1 day post last application. Laryngeal tissue was harvested and sent for blinded pathological examination. Histologic and visual scores were compared to each other and to control- and sham-treated dogs.

RESULTS

Pepsin alone (8.5 +/- 1.66) or combined with CBA (16.63 +/- 1.66) at pH 1-2 resulted in significant (p < 0.001) severe histological inflammation much greater than with other agents. Duodenal ingredients caused no or minimal degree of histological damage at all pH values. Visual scores above subtle erythema were significantly (p < 0.001) higher in the animals exposed to pepsin followed by CBA alone or in combination with pepsin at pH 1-2. There was a significant (p < 0.01) correlation between histology and visual scores (rho = 0.47; 95% CI = 0.30-0.60) for all sites combined. Of the three laryngeal sites, vocal cords were the most sensitive to injury by applied solutions.

CONCLUSIONS

(i) In acidic refluxate, pepsin and CBAs are the most injurious agents affecting laryngeal tissue. (ii) Duodenal agents do not play a significant role in causing laryngeal injury. (iii) Aggressive acid suppression should eliminate the injurious potential of any gastroduodenal refluxate.

Development of Barrett's esophagus six months after total gastrectomy

Barrett's esophagus (BE) is an acquired disease of the esophagus, in which esophageal squamous epithelium is changed by injury from reflux to metaplastic intestinal type columnar epithelium. BE is the premalignant lesion of adenocarcinoma of the esophagus. It is widely accepted that the long-standing reflux of gastric acid is a catalyst for the development of BE. More recent work points toward the reflux of duodenal secretions as a catalyst in this disease process as well. Moreover, the time course for the development of BE once a patient has reflux is not known. Our case challenges the currently defined time course of "long-standing" reflux symptoms for the development of BE, and supports the role of duodenal secretions alone in the development of BE. A 68-yr-old Caucasian man was admitted with weight loss, left upper quadrant pain, a hemoglobin of 6.8, and heme-positive stool. Esophagogastroduodenoscopy (EGD) revealed normal esophageal mucosa and a mass in the gastric cardia. Biopsies showed moderately differentiated gastric adenocarcinoma. The patient underwent a total gastrectomy, distal esophagectomy, and a Roux-en-Y esophagojejunostomy. Pathology confirmed gastric adenocarcinoma (T1 N0 Mx). The distal esophagus and gastroesophageal junction in the resected specimen were grossly and microscopically normal. Six months later an EGD, prompted by new complaints of regurgitation and dyspepsia, revealed distal esophageal mucosa lined by red-colored columnar tissue. Biopsies showed intestinal type epithelium. Thus, our case report's contribution to the current literature is twofold. It provides evidence of development of BE solely from duodenal reflux, and it documents a relatively short time span to development of BE.

Expression and localization of c-Fos and NOS in the central nerve system following esophageal acid stimulation in rats

AIM

To determine the distribution of neurons expressing c-Fos and nitric oxide synthase (NOS) in the central nerve system (CNS) following esophageal acid exposure, and to investigate the relationship between c-Fos and NOS.

METHODS

Twelve Wistar rats were randomly divided into two equal groups. Hydrochloric acid with pepsin was perfused in the lower part of the esophagus for 60 min. As a control, normal saline was used. Thirty minutes after the perfusion, the rats were killed and brains were removed and processed for c-Fos immunohistochemistry and NADPH-d histochemistry. Blood pressure (BP), heart rate (HR), and respiratory rate (RR) during the experimental procedures were recorded every 10 min.

RESULTS

There were no significant differences in BP, HR and RR between the two groups. c-Fos immunoreactivity was significantly increased in rats receiving acid plus pepsin perfusion in amygdala (AM), paraventricular nucleus (PVN), parabrachial nucleus (PBN), nucleus tractus solitarius and dorsal motor nucleus of vagus (NTS/DMV), nucleus ambiguous (NA), reticular nucleus of medulla (RNM) and area postrema (AP). NOS reactivity in this group was significantly increased in PVN, PBN, NTS/DMV, RNM and AP. c-Fos and NOS had significant correlation between PVN, PBN, NTS/DMV, RNM and AP.

CONCLUSION

Acid plus pepsin perfusion of the esophagus results in neural activation in areas of CNS, and NO is likely one of the neurotransmitters in some of these areas.

Effect of splitting the dose of esomeprazole on gastric acidity and nocturnal acid breakthrough

BACKGROUND

Twice-daily dosing is increasingly used to improve gastric acid control, although not all proton-pump inhibitors are more effective when doses are split. Standard dose esomeprazole provides better gastric acid control than other standard dose proton-pump inhibitors.

AIMS

To compare the effect of standard dose esomeprazole (1 x 40 mg) with 20 mg b.d. on gastric acidity.

METHODS

Thirteen healthy subjects participated in this crossover study, receiving esomeprazole 2 x 20 mg and 1 x 40 mg for 7 days in random order with a washout period of at least 7 days. Gastric 24-h pH was measured on days 1, 2 and 6.

RESULTS

Median gastric 24-h pH was higher during 2 x 20 mg esomeprazole on day 2 (P < 0.01), no differences were detected on day 6. Night-time gastric acid suppression was significantly improved by 2 x 20 mg esomeprazole on all study days (P < 0.05). Nocturnal acid breakthrough was observed on all study days in subjects receiving 1 x 40 mg, but in only 85% (first night), 64% (second night), and 45% of subjects (sixth night) with 2 x 20 mg (P < 0.05).

CONCLUSION

Splitting the esomeprazole dose improves initial acid suppression, this effect starts at the first night. Maximal benefit is achieved on day 2, while the effect on night-time acid control is detectable during the entire first week of treatment.

Effect of reflux and esophagitis on esophageal volume and acid clearance in piglets

BACKGROUND/AIMS

The study investigates esophageal motor function and esophageal clearance immediately after surgical induction of reflux in piglets and 8 weeks later after peptic esophagitis has developed.

METHODS

Twenty-four sedated, nonintubated piglets were divided into three groups: sham (laparotomy only), reflux (distal esophageal myotomy), and reflux + esophagitis (8 weeks after myotomy). All animals underwent stationary manometry of the esophagus with a four-lumen perfused assembly after injection of 1-, 2-, and 3-mL boluses of saline and acid into the proximal esophagus. Simultaneous pH monitoring allowed assessment of acid clearance. Wave features and clearance times after saline and acid were compared among groups.

RESULTS

There were minor changes in peristaltic activity of the esophagus after saline boluses in animals with reflux. Acid clearance time was prolonged, especially the time to re-establish resting esophageal pH, in animals with esophagitis. These changes, which were volume-dependent, were related to the loss of peristaltic organization of the esophageal waves. The esophageal wave frequency, amplitude, and duration were only slightly changed by the induction of reflux and by esophagitis.

CONCLUSIONS

The esophagus affected by acid reflux, with or without esophagitis, was capable of near-normal motor responses after boluses of saline. Reflux impaired the peristaltic response to acid, and the effect was more pronounced when reflux and esophagitis were both present. The acid clearance time was also strikingly prolonged in the presence of reflux and esophagitis. The results suggest that long episodes of reflux seen on pH tracings from individuals with esophagitis might be secondary both to acid-related motor dysfunction and large volumes of refluxate.

The acidity index: a simple approach to the measurement of gastric acidity

BACKGROUND

The percentage of time intragastric pH < 4 is a major parameter in evaluating the efficiency of acid-suppressive therapies. This parameter is easy to calculate, but does not identify the actual pH level. Recent studies have recommended the use of the integrated intragastric acidity as a more refined method of assessing intragastric acid control.

AIM

To describe a new parameter, the acidity index, based on the logarithmic aspect of pH calculation, which may overcome the limitations of the percentage of time intragastric pH < 4 and the integrated intragastric acidity.

METHODS

The acidity index was calculated by obtaining the sum of 1000 x % time pH < 1, 100 x % time pH < 2 and >or= 1, 10 x % time pH < 3 and >or= 2 and % time pH < 4 and >or= 3. The total percentage of time pH < 4 and the integrated intragastric acidity were calculated based on previous descriptions. The correlations between these parameters were analysed.

RESULTS

The mean +/- s.d. values were 60% +/- 22% for the percentage of time pH < 4, 172 +/- 178 for the acidity index and 1114 +/- 1176 mmol/L.h for the integrated intragastric acidity. Both the integrated intragastric acidity (r = 0.63) and acidity index (r = 0.70) showed only fair correlation with the percentage of time pH < 4. In contrast, there was a strong positive correlation (r = 0.93) between the acidity index and integrated intragastric acidity.

CONCLUSION

The acidity index is easy to calculate, allows a more accurate assessment of the intragastric acidity than does the percentage of time pH < 4, and is comparable with the more complicated integrated gastric acidity in assessing intragastric pH control.

Changing role of in vivo models in columnar-lined lower esophagus

Columnar-lined lower esophagus (CLE) or Barrett's esophagus (BE) is caused by chronic reflux of the gastrointestinal tract and can progress to invasive adenocarcinoma. However, the pathophysiology, cell of origin, and management of this condition is incompletely understood. This review evaluates the role of in vivo models in resolving these debates. A search was performed on the Ovid and Pub Medline for 1964-2001 and Cochrane Collaboration. The keywords used were adenocarcinoma, animal model, Barrett's esophagus, columnar-lined esophagus, esophageal neoplasms, and esophageal carcinogenesis. All relevant papers were scrutinized and an attempt at tabulation was made. In vivo models have been used at several stages of debate on the pathophysiology of BE. They provide conclusive evidence for its acquired nature secondary to duodenogastroesophageal reflux. The cell of origin of experimental BE may arise from adjacent columnar epithelium, basal layer multipotent cells, or esophageal glands. Experimental work on BE is lacking in assessing therapeutic modalities.

Feline esophagitis secondary to gastroesophageal reflux disease: clinical signs and radiographic, endoscopic, and histopathological findings

Chronic esophagitis due to gastroesophageal reflux (GER) is rarely reported in the cat. This paper describes the clinical signs and diagnostic findings, including radiographic, endoscopic, and histopathological abnormalities, in three young, purebred, male cats with esophagitis presumed to be secondary to GER. Clinical signs included regurgitation, dysphagia, and weight loss. Contrast radiography revealed GER, esophageal dilatation, and decreased motility. Endoscopy showed hyperemia, increased vascularity, ulcers, erosion, and an abnormal lower esophageal sphincter. Histopathological lesions included squamous hyperplasia and dysplasia, erosions, ulcers, and an inflammatory infiltrate of lymphocytes, plasma cells, and neutrophils. Long-term follow-up demonstrated progression of the disease in two of the cats.

Review article: gastric acidity--comparison of esomeprazole with other proton pump inhibitors

Gastric acid suppression is the most effective medical therapy to control acidic gastro-oesophageal reflux: individuals in whom therapy fails usually have inadequate acid suppression. Twenty-four-hour intragastric pH-metry measures the percentage of time that gastric pH is above 4 or 3, the critical thresholds for tissue damage and symptom generation in the distal oesophagus. Effective medical therapy must control gastric acidity throughout the daytime, including the postprandial period. It is therefore useful to report the percentage of patients in whom gastric acidity is controlled above pH 4 for at least 16 out of 24 h. Esomeprazole was compared with standard-dose proton pump inhibitors in healthy volunteers and patients with gastro-oesophageal reflux disease. Esomeprazole, 40 mg daily, was significantly more effective at controlling gastric acidity above pH 4 for more than 16 h than lansoprazole, 30 mg daily (38% of individuals vs. 5%, respectively). Esomeprazole, 40 mg daily, also suppressed gastric acidity more effectively and in more individuals than pantoprazole, 40 mg daily, and rabeprazole, 20 mg daily. Esomeprazole, 20 mg daily, was significantly more effective at controlling gastric acidity than lansoprazole, 15 mg daily. The improved acid control with esomeprazole compared with other proton pump inhibitors is likely to result in superior healing rates and improved symptom relief, with fewer therapy-resistant patients.

The role of pepsin in acid injury to esophageal epithelium

OBJECTIVES

The development of reflux esophagitis in humans is a process resulting from esophageal exposure to refluxed gastric contents. There is no doubt that damage to the esophageal epithelium requires exposure to gastric acid; however, the role of refluxed pepsin as contributor to this damage seems to be underappreciated.

METHODS

The role of physiological concentrations of pepsin was examined in Ussing chambered rabbit esophageal epithelium and in cultured esophageal epithelial cells.

RESULTS

The results of this investigation reaffirmed the ability of pepsin to increase the rate and degree of esophageal cell and tissue damage at acidic pH, although the range of activity was limited to pH < 3.0. Moreover, the increased rate of tissue damage by acidified pepsin rapidly (within 15 min) produced a lesion that was irreversible, whereas, in a similar time frame, acid alone produced a lesion that was completely reversible. This early lesion by acidified pepsin was localized by performance of mannitol fluxes in apparently undamaged esophageal epithelium on light microscopy to the intercellular junctional complex. Further acid produced similar degrees of cell killing as acidified pepsin at pH < 3.0 in rabbit esophageal epithelial cells in suspension but not when growing on coverslips or present within intact epithelium.

CONCLUSIONS

These studies suggest that acidified pepsin plays a key role in the development of reflux esophagitis by producing an early irreversible lesion that results in an increase in paracellular permeability, which indirect evidence suggests is due to damage to the junctional complex. The irreversibility of the increase in paracellular permeability is likely to aid conversion of nonerosive to erosive damage to the epithelium by permitting luminal acid greater access to the basolateral membrane of esophageal epithelial cells, which is known to be acid permeable.

Simultaneous intraesophageal impedance and pH measurement of acid and nonacid gastroesophageal reflux: effect of omeprazole

BACKGROUND & AIMS

Nonacid reflux may explain symptoms in acid-suppressed patients. Simultaneous intraesophageal impedance and pH measurement was used to evaluate the frequencies of postprandial acid and nonacid reflux before and after omeprazole administration.

METHODS

Twelve heartburn patients underwent two 2-hour studies of intraesophageal impedance and pH in the right lateral decubitus position after a refluxogenic meal; session 1 without medication, session 2 after 7 days of omeprazole twice daily. Acid and nonacid reflux were quantified.

RESULTS

Two hundred seventeen reflux episodes were detected before and 261 after omeprazole treatment (P > 0.05). Percentage of acid reflux decreased (from 45% to 3%, P = 0.02) and nonacid reflux increased (from 55% to 97%, P = 0.03) after omeprazole. Heartburn and acid taste were more commonly linked to acid reflux but were also produced by nonacid reflux. Regurgitation was reported equally in acid and nonacid reflux. Delta(pH) > 1 did not help predict the presence of symptoms during nonacid reflux.

CONCLUSIONS

During treatment with omeprazole, postprandial reflux becomes predominantly nonacid. Symptoms are more common with acid reflux but are also produced by nonacid reflux. Simultaneous intraesophageal impedance and pH may be useful in evaluating the role of nonacid reflux in symptoms that persist despite adequate acid suppression.