Integrated acidity and the pathophysiology of gastroesophageal reflux disease

Pharmacokinetics and Pharmacodynamics of Esomezol DR, a New Dual Delayed-Release Formulation of Esomeprazole 20 Mg or 40 Mg, in Healthy Subjects

Background

Esomeprazole, a proton pump inhibitor (PPI), is widely used to treat acid-related disorders, but it has short plasma half-life which can cause insufficient gastric acid suppression, such as nocturnal acid breakthrough. A new dual delayed-release (DR) formulation of esomeprazole (Esomezol DR), was developed to extend the duration of gastric acid suppression.

Purpose

This study aimed to evaluate the pharmacokinetics (PKs) and pharmacodynamics (PDs) of esomeprazole for the DR formulation compared to a conventional enteric-coated (EC) formulation (Nexium) in healthy male subjects.

Methods

Two randomized, open-label, multiple-dose, two-way crossover studies with esomeprazole 20 mg and 40 mg were conducted. Subjects received the DR formulation or the EC formulation once daily for 7 days in each period with a 7-day washout. Serial blood samples were collected up to 24 hours after the 1st dose, and 24-hour intragastric pH was continuously monitored before the 1st dose as baseline and after the 1st and the 7th dose.

Results

In 20 mg and 40 mg dose groups, 38 and 44 subjects completed the study, respectively. The DR formulation exhibited the dual-release pattern of esomeprazole, resulting in more sustained plasma concentration-time profiles compared to the EC formulation. The systemic exposure of esomeprazole for the DR formulation was comparable to that for the EC formulation, showing the similar area under the plasma concentration-time curve. The 24-hour gastric acid suppression was also similar between the two formulations, while the inhibition during night-time (22:00-06:00) showed a better tendency in the DR formulation.

Conclusion

The sustained exposure of esomeprazole in the DR formulation led to well-maintained and higher acid inhibition compared to the EC formulation, especially during the night-time. These results suggest that the DR formulation can be an alternative formulation to the conventional EC formulation, expecting the potential of relieving nocturnal acid-related symptoms.

The relationship between esophageal acidity and symptom frequency in symptomatic nonerosive gastroesophageal reflux disease

The present paper examines the extent to which novel measures of esophageal acid exposure can elucidate possible relationships between symptom perception and esophageal acidity in subjects with nonerosive gastroesophageal reflux disease. Recordings of esophageal pH and symptom occurrence from 20 subjects with nonerosive gastroesophageal reflux disease were analyzed. Interval esophageal acid exposure was calculated in two different ways for the interval that preceded each symptom in each subject. Interval esophageal acidity was calculated as the time-weighted acid concentration for the interval. Interval esophageal acid exposure time was calculated as the percentage of the total recording time that esophageal pH was less than pH 4 for the interval. There was a negative relationship between the probability of a symptom and interval esophageal acid exposure indicating the paradoxical finding that the lower the value of esophageal acid exposure, the higher the probability of a symptom. The time courses of symptoms and cumulative esophageal acidity resolved this paradox by indicating that esophageal acid exposure oscillates between longer periods of low esophageal acid exposure with a high number of symptoms reflecting high esophageal acid sensitivity, and shorter periods of high esophageal acid exposure with fewer symptoms reflecting low esophageal acid sensitivity. Thus, the present analyses show how novel measures of acidity can identify and also resolve a previously unrecognized paradoxical relationship between esophageal acid exposure and symptom frequency in subjects with nonerosive gastroesophageal reflux disease.

Sporadic Fundic Gland Polyps and Gastric Acid Suppression Level

BACKGROUND

Fundic gland polyps (FGPs) are a common endoscopic finding and are known to be associated with proton pump inhibitors (PPIs) use. It is not known if their prevalence is affected by gastric acidity levels. This study aimed to assess whether there is a correlation between FGPs and gastric acidity levels as identified on 24-hour ambulatory impedance-pH studies in patients on PPI therapy.

METHODS

We performed a review of 402 consecutive patients who take at least once daily PPI and underwent esophagogastroduodenoscopy with combined impedance-pH studies in the same setting (time and place) between January 2010 and December 2014. Patients were classified into 2 groups based on the presence or absence of biopsy-confirmed FGPs during endoscopy.

RESULTS

Of the 402 patients, 30 (7%) had FGPs. One of these polyps was found with low-grade dysplasia. There was no significant difference of the distributions of the [H⁺] in the FGPs versus the nonpolyp groups (P = 0.741). There was no significant difference between the 2 groups regarding PPI dose frequency regimens (once and twice) (P = 0.074). However, we found weak ordinal association with PPI duration (P = 0.01) (Spearman = 0.1).

CONCLUSIONS

FGPs are common endoscopic lesions. Incidence of dysplasia in FGPs is not only rare, but also of unknown clinical significance. Although they seem to be associated with PPIs, the mechanism remains unclear, as we found no correlation between the presence of FGPs and gastric acid control or PPI dose. Future studies would be useful to elucidate an alternate mechanism.

Acid Inhibitory Effect of a Combination of Omeprazole and Sodium Bicarbonate (CDFR0209) Compared With Delayed-Release Omeprazole 40 mg Alone in Healthy Adult Male Subjects

CDFR0209, a combination of an immediate-release formulation of omeprazole 40 mg and sodium bicarbonate 1100 mg, has been developed to treat acid-related disorders. We compared the acid inhibitory effects of CDFR0209 and delayed-release omeprazole (omeprazole-DR, Losec 40 mg) after repeated dosing in Helicobacter pylori-negative healthy adult male subjects. In this 2-period crossover study, 30 subjects were randomized to CDFR0209 or omeprazole-DR daily for 7 days. An ambulatory continuous 24-hour intragastric pH recording was performed at baseline and on days 1 and 7 of each administration period. Integrated gastric acidity was calculated from time-weighted average hydrogen ion concentrations at each hour of the 24-hour record. An analysis of variance model was used to test the pharmacodynamic equivalence of CDFR0209 and omeprazole-DR, using the natural logarithmic transformation of the percent decrease from baseline in integrated gastric acidity for the 24-hour interval after the seventh dose of each omeprazole formulation. The geometric least-squares mean ratios (CDFR0209/omeprazole-DR) of the percent decrease from baseline in integrated gastric acidity was 0.98 (90%CI, 0.93-1.07). Both CDFR0209 and omeprazole-DR are equally effective in decreasing integrated gastric acidity at steady state.

Exploring the physiologic role of human gastroesophageal reflux by analyzing time-series data from 24-h gastric and esophageal pH recordings

Our previous finding of a fractal pattern for gastric pH and esophageal pH plus the statistical association of sequential pH values for up to 2 h led to our hypothesis that the fractal pattern encodes information regarding gastric acidity and that depending on the value of gastric acidity, the esophagus can signal the stomach to alter gastric acidity by influencing gastric secretion of acid or bicarbonate. Under our hypothesis values of gastric pH should provide information regarding values of esophageal pH and vice versa. We used vector autoregression, a theory‐free set of inter‐related linear regressions used to measure relationships that can change over time, to analyze data from 24‐h recordings of gastric pH and esophageal pH. We found that in pH records from normal subjects, as well as from subjects with gastroesophageal reflux disease alone and after treatment with a proton pump inhibitor, gastric pH values provided important information regarding subsequent values of esophageal pH and values of esophageal pH provided important information regarding subsequent values of gastric pH. The ability of gastric pH and esophageal pH to provide information regarding subsequent values of each other was reduced in subjects with gastroesophageal reflux disease compared to normal subjects. Our findings are consistent with the hypothesis that depending on the value of gastric acidity, the esophagus can signal the stomach to alter gastric acidity, and that this ability is impaired in subjects with gastroesophageal reflux disease.

We found that in pH records from normal subjects, as well as from subjects with gastroesophageal reflux disease alone and after treatment with a proton pump inhibitor, gastric pH values provided important information regarding subsequent values of esophageal pH and values of esophageal pH provided important information regarding subsequent values of gastric pH. Our findings are consistent with the hypothesis that depending on the value of gastric acidity, the esophagus can signal the stomach to alter gastric acidity, and that this ability is impaired in subjects with gastroesophageal reflux disease.

Clinical trial: gastric acid suppression in Hispanic adults with symptomatic gastro-oesophageal reflux disease - comparator study of esomeprazole, lansoprazole and pantoprazole

BACKGROUND

Hispanic-Americans are a rapidly growing population in the United States, yet gastro-oesophageal reflux disease (GERD) is not well studied in this population.

AIM

To compare the efficacy of esomeprazole, lansoprazole and pantoprazole in suppressing gastric acid, including the area of the 'acid pocket,' in Hispanics with GERD.

METHODS

In this open-label, 3-way crossover study, 83 Hispanics with symptomatic GERD were randomized to 1 of 6 possible treatment sequences of three 5-7-day dosing periods with esomeprazole 40 mg, lansoprazole 30 mg and pantoprazole 40 mg daily separated by 10-17-day washout periods. Intragastric pH was measured for 24 h using dual probes with a distal and proximal (area of the 'acid pocket') electrode.

RESULTS

Esomeprazole suppressed intragastric acid (pH >4.0) significantly longer over 24 h (primary end point) compared with lansoprazole and pantoprazole (P < 0.0001), and proximal gastric acid (pH >4.0) significantly longer over 24 h compared with lansoprazole (P < 0.05) and pantoprazole (P < 0.0001).

CONCLUSIONS

Esomeprazole was more effective than lansoprazole and pantoprazole in suppressing gastric acidity at both intragastric distal and proximal (area of the acid pocket) sites in Hispanics with GERD. Future studies are warranted to understand better the role of the acid pocket in GERD (Clinical trial numbers: D9612L00106; ClinicalTrials.gov: NCT00410592).

Review article: sleep-related gastro-oesophageal reflux as a distinct clinical entity

BACKGROUND

Many patients with chronic gastro-oesophageal reflux disease (GERD) have frequent nighttime heartburn as well as sleep-related gastro-oesophageal reflux (GOR). Sleep-related GOR has been shown to play an important role in the development of oesophagitis and other complications of GOR.

AIM

To present a conceptual argument that nighttime heartburn and associated sleep-related GOR should be recognized as a distinct clinical entity deserving special attention with regard to the diagnosis and treatment of GERD.

METHODS

The data presented come from surveys of GERD patients as well as from physiological studies to include studies monitoring oesophageal pH and spontaneous reflux events during polysomnographically (PSG) monitored sleep.

RESULTS

Evidence is presented to show that nighttime heartburn is prevalent and its occurrence separates patients from those who have heartburn most exclusively in the daytime. The evidence presented also supports the notion that nighttime heartburn sufferers have a more complicated disease and they have a greater risk of developing oesophagitis and other respiratory complications. The data also show that responses to acid mucosal contact are quite different during sleep compared to responses measured during the waking state.

CONCLUSIONS

Nighttime heartburn and GOR represent a distinct clinical entity which deserves specific attention in the diagnosis and optimal treatment of GERD.

Evolving issues in the management of reflux disease?

PURPOSE OF REVIEW

Gastroesophageal reflux disease (GERD) is a common chronic disorder often successfully treated, although there are several evolving issues in management. We reviewed the issues related to unmet needs over the past 12 months.

RECENT FINDINGS

A substantial number of patients fail to respond adequately to once or even twice daily proton pump inhibitor (PPI). There is no standard definition of PPI failure in GERD; a universally accepted definition for treatment success is also not available. Differentiation between erosive esophagitis and nonerosive reflux disease can be made but requires endoscopy; but studies still confuse functional heartburn and nonerosive reflux disease, which impacts management. Acid reflux plays an important role in GERD pathogenesis and the precise role of acid requires more studies of differences between erosive esophagitis and nonerosive reflux disease symptom generation and the implication of nocturnal acidification. Several possible mechanisms may explain GERD refractory to PPIs.

SUMMARY

Management of PPI nonresponders remains a challenge. Objective and precise evaluation of symptoms and treatment response requires study in high-quality trials. New therapeutic approaches are under investigation to answer unmet needs and improve erosive esophagitis healing rates and symptom control.

Continuous distal oesophageal acidification decreases postprandial gastric acidity in healthy human subjects

BACKGROUND

Previously, we hypothesized that exposing the distal oesophagus to acid signals the stomach to decrease gastric acidity.

AIM

To test the hypothesis that exposing the distal oesophagus to acid signals the stomach to decrease gastric acidity.

METHODS

Twenty-two healthy humans ingested a standard meal containing [(14)C]octanoic acid and [(13)C]glycine over 30 min on 2 separate occasions. Gastric pH was measured for 90 min before and 240 min after the meal. 10 mm HCl was infused continuously at 1 mL/min into either the distal oesophagus or stomach in a 2-way crossover fashion for 60 min before and 240 min after the meal. Gastric emptying of solid and liquid were determined with breath tests.

RESULTS

Compared to gastric infusion, oesophageal infusion significantly decreased gastric acidity after the meal, but not before the meal and the magnitude of the decrease varied directly with gastric acidity. Gastric emptying of solid or liquid with oesophageal infusion was not significantly different from that with gastric infusion.

CONCLUSIONS

These findings support the hypothesis of the existence of a physiological oesophago-gastric feedback mechanism that might contribute to regulation of postprandial gastric acidity. Oesophageal acidification might decode gastric information and signal the stomach to decrease gastric acidity. Further studies are needed to assess the characteristics of such feedback mechanism in-patients with gastro-oesophageal reflux disease (GERD).

Predictable prolonged suppression of gastric acidity with a novel proton pump inhibitor, AGN 201904-Z

BACKGROUND

AGN 201904-Z is a new, slowly absorbed, acid-stable pro-proton pump inhibitor (pro-PPI) rapidly converted to omeprazole in the systemic circulation giving a prolonged residence time.

AIM

To investigate pharmacodynamics and pharmacokinetics of AGN 201904-Z compared to esomeprazole.

METHODS

A randomized, open-label, parallel group, investigator-blinded intragastric pH study was conducted in 24 healthy Helicobacter pylori negative male volunteers. AGN 201904-Z enteric-coated capsules (600 mg/day) or esomeprazole delayed-release tablets (40 mg/day) were administered for 5 days. Twenty-four-hour intragastric pH recordings were acquired at baseline, days 1, 3 and 5 with blood levels of omeprazole, AGN 201904-Z and gastrin.

RESULTS

On day 1, median nocturnal pH and proportion of nocturnal time with pH >or=4 and 24-h and nocturnal time pH >or=5 were significantly higher with AGN 201904-Z than esomeprazole. At day 5, 24-h and median nocturnal pH were significantly higher for AGN 201904-Z than esomeprazole (P < 0.0001). There was also a marked reduction in periods of nocturnal pH <4.0. Area under curve of the AGN 201904-Z active metabolite (omeprazole) in the blood was twice that of esomeprazole at day 5.

CONCLUSIONS

AGN 201904-Z produced a significantly greater and more prolonged acid suppression than esomeprazole, and nocturnal acid suppression was more prolonged over all 5 days. AGN 201904-Z should provide true once-a-day treatment and better clinical efficacy than current PPIs.

Mechanisms of acid gastroesophageal reflux in the Japanese population

In contrast to Western countries, reflux esophagitis is considered to be less common in the Orient, including Japan. Transient LES relaxation (TLESR) is a major mechanism of gastroesophageal reflux (GER); however, there are no data on the mechanisms of GER in Japanese people. In addition, it is unclear whether or not the rate of TLESRs, in the sitting position, is higher in reflux esophagitis patients than in healthy subjects. The aim of this study is to determine the mechanisms of acid reflux and the rate of TLESRs, and to compare the rate of acid reflux during TLESRs between healthy volunteers and patients with reflux esophagitis in Japan. Preprandial and postprandial esophageal manometry and pH monitoring were performed in the sitting position in ten healthy volunteers and ten patients with reflux esophagitis of Los Angeles grade C. The energy level of the meal was 692 kcal and consisted of 33% fat. In healthy volunteers, 100% (median) of the acid reflux episodes occurred during TLESRs compared with 55.0% in patients with esophagitis. The remaining reflux episodes in the esophagitis patients were related to straining (12.8%) and absent basal LES pressure (19.5%). The rate of TLESRs in patients with esophagitis was 4.7 h(-1) (3.3-5.7) [median, (interquartile range)] and did not vary significantly from that in healthy volunteers [5.0 h(-1) (4.3-6.3)] 3 h postprandially. The rate of acid reflux during TLESRs in patients with esophagitis (42.7%, median) 3 h postprandially was significantly higher than in healthy volunteers (9.2%). In Japan, the mechanisms of GER in both groups are similar to those reported in Western countries. The rate of acid reflux during TLESRs in patients with reflux esophagitis is significantly higher than in healthy volunteers; however, compared to rates reported in Western countries these rates are very low for both groups.

Relationship between intragastric acid control and healing status in the treatment of moderate to severe erosive oesophagitis

AIM

To assess the relationship between the percentage of time intragastric pH >4.0 and healing of erosive oesophagitis.

METHODS

In this proof-of-concept study, adults with endoscopically verified Los Angeles grade C or grade D erosive oesophagitis were randomly assigned to oral esomeprazole 10 or 40 mg once daily for 4 weeks. On day 5, patients underwent 24-h pH monitoring. At 4 weeks, erosive oesophagitis healing status was endoscopically assessed. Investigators scored gastro-oesophageal reflux disease symptoms on a 4-point scale [none to severe (0-3)] before and 4 weeks after treatment. The percentage of time intragastric pH was >4.0 and healing status were correlated and tested for significance using a Spearman rank correlation (r).

RESULTS

103 patients had evaluable data (mean age, 48.7 years; 65% men). Mean percentages of time with intragastric pH >4.0 on day 5 in patients with healed and unhealed erosive oesophagitis were 61% and 42%, respectively (P = 0.0002), indicating that erosive oesophagitis healing rates were positively related to the percentage of time intragastric pH was >4.0. Greater intragastric acid control correlated with lower final daytime and night-time heartburn and acid regurgitation symptom scores (r = -0.029, -0.029 and -0.021; P = 0.003, 0.003 and 0.032, respectively).

CONCLUSION

A positive relationship between intragastric acid control and erosive oesophagitis healing was demonstrated.

ACG practice guidelines: esophageal reflux testing

Investigations and technical advances have enhanced our understanding and management of gastroesophageal reflux disease. The recognition of the prevalence and importance of patients with endoscopy-negative reflux disease as well as those refractory to proton pump inhibitor therapy have led to an increasing need for objective tests of esophageal reflux. Guidelines for esophageal reflux testing are developed under the auspices of the American College of Gastroenterology and its Practice Parameters Committee and approved by the Board of Trustees. Issues regarding the utilization of conventional, catheter-based pH monitoring are discussed. Improvements in the interpretation of esophageal pH recordings through the use of symptom-reflux association analyses as well as limitations gleaned from recent studies are reviewed. The clinical utility of pH recordings in the proximal esophagus and stomach is examined. Newly introduced techniques of duodenogastroesophageal reflux, wireless pH capsule monitoring and esophageal impedance testing are assessed and put into the context of traditional methodology. Finally, recommendations on the clinical applications of esophageal reflux testing are presented.

Comparison of the effects of immediate-release omeprazole oral suspension, delayed-release lansoprazole capsules and delayed-release esomeprazole capsules on nocturnal gastric acidity after bedtime dosing in patients with night-time GERD symptoms

BACKGROUND

Gastro-oesophageal reflux disease (GERD) patients on proton pump inhibitors before breakfast or dinner have acid recovery at night. Bedtime immediate-release omeprazole (IR-OME) demonstrated better control of nocturnal pH than pantoprazole before dinner.

AIM

To compare repeated once daily bedtime dosing of IR-OME, lansoprazole and esomeprazole on nocturnal gastric acidity.

METHODS

Open-label, randomized, crossover study enrolling 54 patients with nocturnal GERD symptoms comparing IR-OME, lansoprazole and esomeprazole at steady state for nocturnal acid breakthrough (NAB), percentage of time with gastric pH > 4 and median gastric pH.

RESULTS

Onset of nocturnal acid control with IR-OME was rapid. During the first half of the night, percentage of time with gastric pH > 4 and median gastric pH were significantly higher after IR-OME compared to esomeprazole or lansoprazole (P < 0.001, both comparisons). Over the 8-h night-time period, acid control with IR-OME was significantly better than lansoprazole (P < 0.001), and comparable to esomeprazole. IR-OME reduced NAB compared with esomeprazole and lansoprazole (61% vs. 92% and 92%; P < 0.001, both comparisons).

CONCLUSIONS

Bedtime IR-OME provided more rapid control of night-time gastric pH and decreased NAB compared with esomeprazole and lansoprazole. Nocturnal acid control with IR-OME was superior to lansoprazole and comparable to esomeprazole. Bedtime dosing with IR-OME may be effective for patients with night-time heartburn.

Comparison of the effects of single and repeated oral doses of lansoprazole and rabeprazole on ambulatory 24-hour intragastric pH in healthy volunteers

BACKGROUND

As the comparative pharmacokinetics and pharmacodynamics of lansoprazole and rabeprazole have not previously been studied, we set out in this study to compare the pharmacokinetics and pharmacodynamics of single and repeated daily doses of lansoprazole 15 mg and 30 mg with those of rabeprazole 10 mg and 20 mg.

METHODS

This was an open-label, randomised, crossover, two-centre study in 72 healthy volunteers. Each subject received each of the four treatments for 5 days, with 2-week washout periods. Continuous 24-hour intragastric pH and pharmacokinetics were studied on days 1 and 5.

RESULTS

Mean 24-hour pH and percentage time for pH > 4 were not significantly different between lansoprazole 30 mg and rabeprazole 20 mg. Mean 24-hour pH and percentage time for pH > 4 were significantly greater after lansoprazole 30 mg and rabeprazole 20 mg than after lansoprazole 15 mg and rabeprazole 10 mg, respectively. Lansoprazole resulted in greater acid suppression during hours 0-5 on days 1 and 5, whereas rabeprazole had greater suppression during hours 11-24 on day 5. Time to maximum plasma concentration was significantly shorter for lansoprazole on both days.

CONCLUSION

Lansoprazole had a consistently faster onset of action, whereas rabeprazole had a greater effect during the evening hours after 5 days of administration.

Intragastric acidity after switching from 5-day treatment with intravenous pantoprazole 40 mg/d to 5-day treatment with oral esomeprazole 40 mg/d or pantoprazole 40 mg/d: an open-label crossover study in healthy adult volunteers

BACKGROUND

After a course of IV proton pump inhibitor therapy, patients might require continued oral antisecretory therapy. A direct comparison of therapeutic alternatives could assist physicians in decisions regarding optimal acid-suppressive therapy. Oral esomeprazole might control intragastric acidity more effectively compared with other acid-suppressive agents after IV therapy.

OBJECTIVE

The aim of this study was to compare intragastric acid control on day 5 of administration of esomeprazole magnesium versus pantoprazole 40 mg PO QD after switching from 5 days of treatment with pantoprazole 40 mg IV in healthy volunteers.

METHODS

This randomized, open-label, comparative, 2-way crossover study was conducted at the Oklahoma Foundation for Digestive Research, Oklahoma City, Oklahoma, between October and December 2004. Healthy, Helicobacter pylori-negative adults were randomly assigned to 1 of 2 dosing sequences: pantoprazole IV followed by esomeprazole PO or pantoprazole IV followed by pantoprazole PO. All study medications were administered for 5 days at a dose of 40 mg QD. IV pantoprazole was administered over 2 minutes; all medications were administered 30 minutes before breakfast. There was a 10- to 21-day washout period between each 10-day dosing period. All doses were administered at the study site. Before oral study drug administration on days 1 and 5, 24-hour pH monitoring was performed using a pH catheter positioned 10 cm distal to the lower esophageal sphincter in the stomach. The primary end point was percentage of time with pH >4 (%t pH >4) during the 24-hour pH-monitoring period. Tolerability was assessed using spontaneous reporting, laboratory analysis, and vital-sign measurement.

RESULTS

Of 42 subjects randomized to treatment sequences, 4 were withdrawn during the study because of invalid pH data; 38 subjects (24 men, 14 women; mean [SD] age, 25.2 [8.1] years) had assessable data. Day-5 %t pH >4 was 68.5% with esomeprazole and 53.3% with pantoprazole (P < 0.001). Day-1 %t pH >4 was 62.5% with esomeprazole and 51.0% with pantoprazole (P < 0.001). The most common adverse events were rhinitis (2 subjects each with pantoprazole IV and PO; 1 subject with esomeprazole) and headache (2 subjects with esomeprazole; 1 subject with pantoprazole IV).

CONCLUSIONS

The results of this study in healthy adult volunteers suggest that switching from pantoprazole 40 mg IV to esomeprazole 40 mg PO QD more effectively suppresses intragastric acid compared with switching from pantoprazole 40 mg IV to pantoprazole 40 mg PO QD. All 3 treatments were well tolerated.

Intragastric acid control in non-steroidal anti-inflammatory drug users: comparison of esomeprazole, lansoprazole and pantoprazole

BACKGROUND

Studies to date have not directly compared the pharmacodynamic efficacies of different proton pump inhibitors in controlling intragastric acidity in patients treated with non-steroidal anti-inflammatory drugs.

AIM

To compare acid suppression with once-daily esomeprazole 40 mg, lansoprazole 30 mg and pantoprazole 40 mg in patients receiving non-selective or cyclo-oxygenase-2-selective non-steroidal anti-inflammatory drug therapy.

METHODS

In this multicentre, open-label, comparative, three-way crossover study, adult patients (n = 90) receiving non-steroidal anti-inflammatory drugs were randomized to one of six treatment sequences. At the study site, patients were administered esomeprazole 40 mg, lansoprazole 30 mg and pantoprazole 40 mg for 5 days each, with a washout period of > or =10 days between each treatment. Twenty-four-hour pH testing was performed on day 5 of each dosing period.

RESULTS

The mean percentage of time during the 24-h pH monitoring period that gastric pH was >4.0 was significantly greater with esomeprazole (74.2%) compared with lansoprazole (66.5%; P < 0.001) and pantoprazole (60.8%; P < 0.001), and significantly greater with esomeprazole (P < 0.05) than with the comparators regardless of whether using non-selective vs. cyclo-oxygenase-2-selective non-steroidal anti-inflammatory drugs.

CONCLUSIONS

At the doses studied, esomeprazole treatment provides significantly greater gastric acid suppression than lansoprazole or pantoprazole in patients receiving non-selective or cyclo-oxygenase-2-selective non-steroidal anti-inflammatory drugs.

Analysis of the acidity index and integrated intragastric acidity in 645 patients presenting with gastroesophageal reflux disease symptoms

OBJECTIVE

In a recent study of patients receiving proton-pump inhibitor (PPI) therapy, a new parameter, the acidity index, was described as being less complicated to calculate and of comparable accuracy (r = 0.93) to integrated intragastric acidity (IA) in assessing intragastric pH control. The aim of this study was to correlate AI with IA using a large database of ambulatory 24-h pH-metry studies in untreated patients presenting with gastroesophageal reflux disease (GERD) symptoms.

MATERIAL AND METHODS

We retrospectively analyzed 645 studies obtained from 1995 to 2001. Daytime (0800 h-2200 h), night-time (2200 h-0800 h) and 24-h IA and AI were calculated according to age, gender and the presence or absence of GERD, and correlations between these parameters were assessed using linear regression with F-statistic values, p-values and Akaike's Information Criterion values. GERD was defined as total esophageal pH time <4.0, 5 cm above the lower esophageal sphincter, for > or =4.2% of the day. IA and AI were calculated as follows: IA (mmol x h/l) = summation operator(acid in mmol/l at time "t" + acid in mmol/l at time "t - 1")/2 x ("t"-"t - 1"); AI = (%time pH < 4-%time pH < 3) x 1+(%time pH < 3-%time pH < 2) x 10+(%time pH < 2-%time pH < 1) x 100 + (%time pH < 1-%time pH < 0.8) x 1000.

RESULTS

Overall, the mean 24-h IA value was 882.0+/-820.0 mmol x h/l (daytime 392.0+/-400.0, night-time 490.0+/-486.0). The mean 24-h AI value was 102.0+/-87.0 (daytime 86.0+/-80.0, night-time 120.0+/-114.0, p < 0.001). The mean 24-h IA value was 1057.0+/-829.4 mmol x h/l (daytime 459.8+/-406.0, night-time 597.2+/-500.4, p < 0.001) in GERD patients and 713.0+/-775.0 mmol x h/l (daytime 326.0+/-383.0, night-time 387.0+/-448.5) in non-GERD patients (p < 0.001). The mean 24-h AI value was 122.1+/-88.1 (daytime 101.4+/-82.5, night-time 145.3+/-120.7) in GERD patients and 83.0+/-81.0 (daytime 71.0+/-73.9, night-time 96.4+/-102.6) in non-GERD patients (p < 0.001). Our statistical modeling demonstrated that the correlation between the acidity index and IA becomes progressively poorer with increasing values of acidity.

CONCLUSIONS

We conclude that gastric acid production assessed by both IA and AI is higher during evening hours in comparison with daytime hours and the difference between night-time and daytime values is statistically significant. In addition, gastric acid production assessed by both IA and AI is significantly higher in GERD patients than non-GERD patients. This difference is primarily due to differences in nocturnal acid production. The AI correlates poorly with measured IA, especially at higher levels of gastric acidity. Therefore, AI is not an acceptable surrogate for IA in assessing gastric acid production.

The effects of changing temperature correction factors on measures of acidity calculated from gastric and oesophageal pH recordings

BACKGROUND

Recently, Medtronic notified customers that new correction factors should be used for their Slimline and Zinetics24 single-use, internal-standard pH catheters.

AIM AND METHODS

We selected 24-h recordings of oesophageal and gastric pH with the Zinetics24 from our archives for five healthy subjects and for five gastro-oesophageal reflux disease subjects who were studied at baseline and again after 8 days of treatment with a proton-pump inhibitor. All pH values obtained with the old correction factors were rescaled using the new correction factors. Values for median pH, integrated acidity and time pH < or = 4 were then calculated from pH values with old and new correction factors.

RESULTS

The new correction factors changed values for median pH, integrated acidity and time pH < or = 4. Values for median pH and integrated acidity changed in a predictable, proportionate way, whereas values for time pH < or = 4 did not.

CONCLUSIONS

The new correction factors will not change the interpretation of previously published results with median pH or integrated acidity. In contrast, values for time < or =4 cannot be converted in an obvious way with the new correction factors. Instead, the raw pH data will need to be rescaled and values for time pH < or = 4 recalculated using the rescaled pH data.

The fractal nature of human gastro-oesophageal reflux

BACKGROUND

We are unaware of the analyses of time series data resulting from 24 h recordings of human gastric or oesophageal pH. As a result, we have no understanding of the quantitative changes in gastric or oesophageal acidity over time, the patterns that might characterize these changes, or the physiological significance of gastro-oesophageal reflux.

AIM

To examine the time series for gastric and oesophageal pH.

METHODS

Detrended fluctuation analysis and lag analysis were used to analyse data from 24 h recordings of oesophageal and gastric pH in five normal subjects and five subjects with gastro-oesophageal reflux disease.

RESULTS

Analyses of the patterns of gastric and oesophageal pH over time in normal subjects and subjects with gastro-oesophageal reflux disease indicate that the fluctuations in pH are self-similar across different time scales and are consistent with an underlying fractal process. Furthermore, there is a significant statistical association between sequential pH values separated by as much as 2.2 h.

CONCLUSIONS

We hypothesize that the self-similar, fractal pattern encodes information about gastric acidity and that the oesophagus decodes this information and, when appropriate, may signal the stomach to reduce gastric acidity. Subjects with gastro-oesophageal reflux disease might have an impaired oesophageal-gastric feedback mechanism that results in increased gastric acid, which reflux from the stomach into the oesophagus.

Effect on intragastric pH of a PPI with a prolonged plasma half-life: comparison between tenatoprazole and esomeprazole on the duration of acid suppression in healthy male volunteers

OBJECTIVE

To compare the inhibitory effect of a novel proton pump inhibitor (PPI), tenatoprazole 40 mg once daily, with esomeprazole 40 mg once daily on intragastric acidity.

METHODS

A randomized, investigator-blind, two-way, crossover study was conducted in 30 healthy Helicobacter pylori negative male volunteers. Tenatoprazole 40 mg or esomeprazole 40 mg was administered once daily for 7 consecutive days with a 4-wk washout period between treatments. Ambulatory 24-h intragastric pH was recorded at baseline, after 7 days' treatment, and 3 and 5 days after treatment was stopped.

RESULTS

At presumed steady-state (day 7), median 24-h pH values were 5.02 and 4.79 for tenatoprazole and esomeprazole, respectively. There was a significant difference between tenatoprazole and esomeprazole during the nocturnal period when mean pH was 4.64 +/- 0.67 versus 3.61 +/- 0.90, respectively (p < 0.0001), as well as a significantly higher mean percentage of time with pH >4 on tenatoprazole (72.5 +/- 14.9 vs 62.2 +/- 13.6, p < 0.0001). The effect of tenatoprazole was still present 5 days after treatment withdrawal especially during the night-time. The mean area under the plasma concentration-time curve and elimination half-time was significantly higher in the tenatoprazole group as compared with the esomeprazole group.

CONCLUSION

Tenatoprazole 40 mg daily provides a prolonged duration of acid suppression and a shorter nocturnal acid breakthrough in healthy volunteers, even after stopping the drug. Thus, tenatoprazole may provide greater clinical efficacy for patients in whom a once daily PPI is ineffective. Further studies are indicated.

Postprandial oesophageal integrated acidity is a reliable predictor of gastro-oesophageal reflux disease

BACKGROUND

Measurement of oesophageal acid exposure parameters postprandially has been shown to distinguish gastro-oesophageal reflux disease patients from normal individuals.

AIMS

To calculate the accuracy of postprandial oesophageal integrated acidity in diagnosing gastro-oesophageal reflux disease.

METHODS

Ambulatory 24-h pH studies of 626 patients were analysed retrospectively. Gastro-oesophageal reflux disease, defined as pH < 4 for > 4.2% of time, was identified in 305 subjects. Postprandial oesophageal integrated acidity was measured for 2 and 3 h after the largest meal peak as determined from gastric pH. Postprandial symptom-associated probability was calculated.

RESULTS

Gastro-oesophageal reflux disease subjects had a greater postprandial oesophageal integrated acidity than non-gastro-oesophageal reflux disease subjects [median (IQR): 0.57 (0.08-2.66) vs. 0.03 (0.01-0.15) mmol*h/L]. Median postprandial oesophageal integrated acidity did not differ with gender or age in gastro-oesophageal reflux disease and non-gastro-oesophageal reflux disease subjects (P > 0.05 for all). A 3-h postprandial oesophageal integrated acidity value of 0.121 mmol*h/L had a 71.1% sensitivity and 71.7% specificity in diagnosing gastro-oesophageal reflux disease. Gastro-oesophageal reflux disease subjects with symptoms had a higher postprandial oesophageal integrated acidity than those without (P = 0.043), whereas non-gastro-oesophageal reflux disease subjects with and without symptoms did not differ (P = 0.74). The correlation between symptom-associated probability and postprandial oesophageal integrated acidity was poor (gastro-oesophageal reflux disease: r = 0.15; non-gastro-oesophageal reflux disease: r = 0.25).

CONCLUSION

Postprandial oesophageal integrated acidity provides a robust estimation of oesophageal acid exposure and may predict symptoms in gastro-oesophageal reflux disease patients.

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

BACKGROUND

Postprandial intragastric acidity is not uniform. Postprandial proximal gastric acid pockets have been described in the present study.

AIM

To determine the effects of rabeprazole on regional intragastric acidity and proximal acid pockets.

METHODS

Ten normal subjects underwent two 8-day oral dosing regimens with placebo or rabeprazole 20 mg each morning in a randomized, double-blind protocol. Oesophago-gastric pH monitoring was performed on days 1 and 8.

RESULTS

Rabeprazole increased fasting and postprandial gastric pH to above 4 in each area of the stomach on days 1 and 8. With placebo, acid pockets were identified at the cardia/gastro-oesophageal junction in 62 and 50 of 150 pull-throughs on days 1 and 8, respectively. Acid pockets were detected postprandially 3.1 +/- 0.2-5.8 +/- 0.1 cm below the proximal border of the lower oesophageal sphincter with a mean pH drop from 4.6 +/- 0.1 to 1.5 +/- 0.1. Rabeprazole decreased the number of acid pockets to 30 and 27 on days 1 and 8, respectively. Rabeprazole also decreased their length and magnitude of the pH drop.

CONCLUSIONS

Rabeprazole increased intragastric pH on day 1 and 8 and maintained an elevated pH during and after meals. Postprandial acid pockets, identified in the region of the cardia/gastro-oesophageal junction area postprandially, were decreased in number, length and magnitude by rabeprazole.

Catheter-based pH monitoring: use in evaluation of gastroesophageal reflux disease symptoms (on and off therapy)

Tube-based ambulatory pH testing has rapidly evolved in the past 3 decades to become the standard by which other diagnostic approaches to gastroesophageal reflux disease are judged. Acid exposure 5 cm above the manometrically determined lower esophageal sphincter is the standard for documentation of pathologic acid exposure of the distal esophagus. Proximal esophageal or hypopharyngeal monitoring is an evolving technique that may shed light on patients with supraesophageal symptoms. The ability to simultaneously monitor esophageal and gastric acidity (usually in patients with persistent symptoms despite therapy) is another advantage of this technique. Whether the new system that allows simultaneous pH and impedance monitoring and the system that uses an implantable tubeless monitoring capsule will supplant this older but well-established technology remains to be determined.

Clinical relevance of esophageal and gastric pH measurements in patients with gastro-esophageal reflux disease (GERD)

BACKGROUND

Gastro-esophageal reflux disease (GERD) is a highly prevalent disease caused by the exposure of the esophagus to refluxed gastric contents. Proton pump inhibitors (PPIs) are the mainstay of current treatment. At present, the assessment of the efficacy of different PPIs in the treatment of GERD employs two measures: esophageal and gastric pH monitoring. Esophageal pH monitoring is the most accurate method of detecting reflux episodes and, therefore, its role as a diagnostic modality is well accepted. Gastric pH monitoring, on the other hand, is an accurate measure of gastric acid pH, but its relevance to patients with GERD is questionable, since recordings correlate poorly with esophageal acid exposure.

OBJECTIVE

This paper reviews (based on a Medline literature search, 1980-2004) the clinical relevance of esophageal and gastric pH measurements in both the management of GERD and in the evaluation of the efficacy of PPI therapy.

FINDINGS AND CONCLUSIONS

Evidence presented suggests that the assessment of esophageal pH yields data of greater relevance to patients with GERD than does data from gastric pH. This largely arises from the fact that esophageal pH monitoring assesses the pH of the refluxate and the frequency of reflux episodes at the mucosal site affected by the disease. The use of esophageal pH monitoring is recommended in patients who fail to present with endoscopic evidence of esophagitis, those with extra-esophageal symptoms, those who have failed traditional anti-reflux therapies, and those who are potential candidates for anti-reflux surgery. In recent years, the technique has benefited from the development of a wireless pH probe, and there is also an increasing body of evidence supporting its use in combination with other emerging technologies, such as Bilitec monitoring and multichannel intraluminal impedance. Such an approach is anticipated to aid both the diagnosis of GERD and the characterization of gastro-esophageal reflux (GER) in these patients.

Frequency analyses of gastric pH in control and gastro-oesophageal reflux disease subjects treated with a proton-pump inhibitor

BACKGROUND

We are unaware of any solid theoretical or pathophysiological basis for selecting pH 4 or any other pH value to assess gastric acidity.

AIM

To examine the frequency of different gastric pH values in control and GERD subjects.

METHODS

Gastric pH was measured for 24 h in 26 control subjects, 26 gastro-oesophageal reflux disease subjects at baseline and the same 26 gastro-oesophageal reflux disease subjects during treatment with a proton-pump inhibitor. Histograms were constructed using the 21 600 values generated from each recording and bins of 0.25 pH units.

RESULTS

The distribution of gastric pH values in gastro-oesophageal reflux disease subjects was significantly different from that in controls and in some instances the distributions detected significant differences that were not detected by integrated acidity. Proton-pump inhibitor treatment significantly altered the distribution of gastric pH values and the nature of this alteration during the postprandial period was different from that during the nocturnal period. Using time pH< or =4 can significantly underestimate the magnitude of inhibition of gastric acidity caused by a proton-pump inhibitor.

CONCLUSIONS

The distribution of gastric pH values provides a rationale for selecting a particular pH value to assess gastric acidity. In some instances, the distribution of gastric pH values detects significant differences between gastro-oesophageal reflux disease and normal subjects that are not detected by integrated acidity.

Oesophageal pH has a power-law distribution in control and gastro-oesophageal reflux disease subjects

BACKGROUND

We are unaware of any solid theoretical or pathophysiological basis for selecting pH 4 or any other pH value to assess oesophageal acid exposure or to define oesophageal reflux episodes.

AIM

To examine the frequency of different oesophageal pH values in control and GERD subjects.

METHODS

Oesophageal pH was measured for 24 h in 57 gastro-oesophageal reflux disease subjects and 26 control subjects. Histograms were constructed using the 21,600 values from each recording and bins of 0.25 pH units.

RESULTS

Compared with controls, gastro-oesophageal reflux disease subjects had significantly more low pH values and significantly fewer high pH values. In both gastro-oesophageal reflux disease and control subjects, the frequency of oesophageal pH values was characterized by a power-law distribution indicating that the same relationship that describes low pH values also describes high pH values, as well as all values in between.

CONCLUSIONS

The distribution of oesophageal pH values indicates that a variety of different pH values can be used to assess oesophageal acid exposure, but raises important questions regarding how oesophageal reflux episodes are defined.

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.

The basis for the decreased response to proton pump inhibitors in gastro-oesophageal reflux disease patients without erosive oesophagitis

BACKGROUND

The reason why heartburn in gastro-oesophageal reflux disease subjects without oesophagitis is less responsive to proton pump inhibitors than heartburn in those with erosive oesophagitis is not known.

METHODS

Gastric and oesophageal pH were determined in 26 subjects with gastro-oesophageal reflux disease at baseline and on days 1, 2 and 8 of treatment with 20 mg omeprazole or 20 mg rabeprazole in a randomized, two-way cross-over fashion. The presence or absence of erosive oesophagitis at baseline was documented by upper gastrointestinal endoscopy.

RESULTS

At a given value of the integrated gastric acidity during treatment with a proton pump inhibitor, the probability of pathological oesophageal reflux was significantly higher in subjects with no oesophagitis than in those with erosive oesophagitis. This occurred because the post-prandial gastric acidity in subjects with no oesophagitis showed a decreased response to the antisecretory agent.

CONCLUSIONS

Compared with gastro-oesophageal reflux disease subjects with erosive oesophagitis, those with no oesophagitis are relatively refractory to the pharmacodynamic effects of proton pump inhibitors on the post-prandial integrated gastric acidity.

Influence of age and gender on gastric acid secretion as estimated by integrated acidity in patients referred for 24-hour ambulatory pH monitoring

OBJECTIVES

Earlier studies have suggested that gastric acid secretion declines with age. Integrated acidity (IA) calculated from ambulatory 24-h pH studies provides an estimation of gastric acid secretion that is less cumbersome than nasogastric aspiration. The aim of this study was to calculate IA as a function of age and gender.

METHODS

In a retrospective study, 753 ambulatory 24-h pH studies from 1994 to 2001 were analyzed. Subjects were classified according to nine age groups: <35 yr (n = 124), 35-39 yr (n = 90), 40-44 yr (n = 92), 45-49 yr (n = 111), 50-54 yr (n = 96), 55-59 yr (n = 61), 60-64 yr (n = 59), 65-69 yr (n = 42), and > or =70 yr (n = 64). Basal integrated acidity (BIA) was defined as IA between 12 midnight and 8 AM when no meals were consumed. Daytime and nocturnal IA/h was measured from 8 AM to 8 PM and from 8 PM to 8 AM. Postprandial IA (PIA) was measured for 2 h after the largest meal peak in each patient.

RESULTS

Gender distribution was similar between groups (chi(2) = 6.42, 3 df, p = 0.093). Mean gastric pH was similar between genders (2.96 +/- 1.36 women; 3.01 +/- 1.42 men; p = 0.71). Women and men had similar BIA (361.1 +/- 384.1 vs 434.6 +/- 436.6 mmol/L/h, p = 0.10), daytime IA (33.5 +/- 33.0 vs 34.1 +/- 33.7 mmol/L, p = 0.90) and nocturnal IA (43.3 +/- 42.1 vs 48.0 +/- 46.6 mmol/L, p = 0.42), and PIA (38.2 +/- 58.7 vs 36.0 +/- 58.5 mmol/L/h, p = 0.47). Mean gastric pH, daytime and nocturnal IA, BIA, and PIA did not differ between age groups (p > 0.1). None of the parameters studied had a linear association with age (mean gastric pH, r = 0.106; BIA, r = -0.124; daytime IA, r = -0.046; nocturnal IA, r = -0.104; PIA, r = -0.117).

CONCLUSIONS

Based on this study, we conclude that IA is unaffected by gender or age.

Heartburn severity can predict pathologic oesophageal reflux in gastro-oesophageal reflux disease patients treated with a proton-pump inhibitor

BACKGROUND

In gastro-oesophageal reflux disease (GERD) subjects treated with a gastric anti-secretory agent, it is not known whether there is a relationship between heartburn severity and oesophageal acid exposure.

METHODS

Oesophageal pH and heartburn severity were determined in 27 GERD subjects at baseline and on days 1, 2 and 8 of treatment with 20 mg omeprazole or 20 mg rabeprazole in a randomized, two-way crossover fashion.

RESULTS

Receiver operating characteristic (ROC) analysis was used to determine values for heartburn severity that gave optimal cut-off points for distinguishing between normal and pathologic oesophageal reflux. Using these cut-off points, we found that the probability of no pathologic oesophageal reflux (Y) could be best fitted by an exponential equation: Y = a(e-bX) + c, where a, b and c are constants and X is the value of heartburn severity. There was close agreement between predicted and observed percentages of subjects with pathologic oesophageal reflux during different days of treatment.

CONCLUSIONS

In GERD subjects treated with a proton-pump inhibitor, the value of heartburn severity following a single standard meal can predict the likelihood of pathologic oesophageal reflux over the entire 24-h period.

Determination of the reduction in gastric acidity necessary to prevent pathological oesophageal reflux in patients with gastro-oesophageal reflux disease treated with a proton pump inhibitor

BACKGROUND

In subjects with gastro-oesophageal reflux disease treated with a gastric antisecretory agent, the extent to which gastric acidity needs to be reduced to prevent pathological oesophageal acid exposure is not known.

METHODS

Gastric and oesophageal pH were measured in 26 healthy subjects and in 59 subjects with gastro-oesophageal reflux disease. In 27 of the subjects with gastro-oesophageal reflux disease, pH was also recorded on days 1, 2 and 8 of treatment with 20 mg omeprazole and 20 mg rabeprazole in a randomized, two-way, cross-over fashion.

RESULTS

Receiver operating characteristic analysis was used to determine values for the integrated oesophageal acidity and time oesophageal pH<or=4 that gave optimal cut-off points for distinguishing between normal and pathological oesophageal reflux. Using these cut-off points, we found that the probability of no pathological oesophageal reflux (Y) could be best fitted by an exponential equation, Y = a(e-bX) + c, where a, b and c are constants and X is the value of the integrated gastric acidity. There was close agreement between the predicted and observed percentages of subjects with pathological oesophageal reflux during different days of treatment.

CONCLUSIONS

In subjects with gastro-oesophageal reflux disease treated with a proton pump inhibitor, the value of the integrated gastric acidity can predict the likelihood of pathological oesophageal reflux.

Meal-stimulated gastric acid secretion and integrated gastric acidity in gastro-oesophageal reflux disease

BACKGROUND

No current methods exist to determine meal-stimulated gastric acid secretion in humans under conditions that approximate those of daily living with the ingestion of breakfast, lunch and dinner.

METHODS

Gastric and oesophageal pH were measured in 26 healthy subjects and in 59 subjects with gastro-oesophageal reflux disease. Meal-stimulated gastric acid secretion was calculated from the buffer capacity of the meals determined in vitro and from the time required for the gastric pH to decrease to pH 2 in vivo following ingestion of the meal.

RESULTS

There was a significant correlation between gastric secretion with each meal and the corresponding post-prandial integrated gastric acidity. There was also a significant correlation between meal-stimulated gastric secretion and integrated gastric acidity from 09.00 to 22.00 h in both subjects with gastro-oesophageal reflux disease and controls. In subjects with gastro-oesophageal reflux disease, gastric secretion and integrated gastric acidity from 09.00 to 22.00 h were significantly higher than those in controls. There was a significant correlation between oesophageal acidity and integrated gastric acidity from 09.00 to 22.00 h in subjects with gastro-oesophageal reflux disease.

CONCLUSIONS

As post-prandial gastric acidity is increased in subjects with gastro-oesophageal reflux disease, it seems likely that increased gastric acidity is an important aetiological factor in this disease.

Cisapride inhibits meal-stimulated gastric acid secretion and post-prandial gastric acidity in subjects with gastro-oesophageal reflux disease

BACKGROUND AND AIMS

KCNQ1 potassium channels in human gastric parietal cells are thought to be involved in gastric acid secretion. As cisapride can inhibit similar channels in other tissues and is an effective treatment for nocturnal heartburn, we examined the effects of cisapride on gastric and oesophageal acidity, gastric emptying and heartburn severity in subjects with gastro-oesophageal reflux disease.

METHODS

Subjects (n = 11) had suffered from heartburn four times or more per week for at least 6 months. Gastric pH and oesophageal pH were measured before, during and after a standard meal ingested over 15 min. Each subject received placebo or 10 mg cisapride orally, 30 min before the beginning of the meal. Meal-stimulated gastric acid secretion was calculated from the amount of HCl required to titrate the homogenized standard meal to pH 2 in vitro and the time required for the pH of the ingested meal to decrease to pH 2 in vivo. Heartburn severity was assessed at 15-min intervals beginning at the end of the meal. Gastric emptying of solids was measured using a [(13)C]-octanoic acid breath test.

RESULTS

Cisapride significantly decreased meal-stimulated gastric acid secretion by 20%, decreased integrated gastric and oesophageal acidity by 50-60% and transiently increased the expiration of (13)CO(2). Cisapride did not significantly alter heartburn severity.

CONCLUSIONS

The cisapride-induced decreases in meal-stimulated gastric acid secretion, gastric acidity and oesophageal acidity in subjects with gastro-oesophageal reflux disease can account for its beneficial clinical effects. These results also raise the possibility that gastric KCNQ1 potassium channels are important in meal-stimulated gastric acid secretion and possibly in the pathophysiology of gastro-oesophageal reflux disease.

Gastroesophageal reflux disease

Gastroesophageal reflux disease (GERD) affects many patients and has a negative effect on quality of life. Along with the increasing prevalence of GERD is an increase in GERD-related complications, including Barrett esophagus and esophageal adenocarcinoma. The past year has yielded new insights into the pathophysiology of GERD that can help us to better understand the relationship between reflux episodes and symptoms of mucosal damage and to provide a tailored treatment targeting individual pathophysiologic defects. The issues addressed in this report include gastric secretory and motor dysfunction; failure of the antireflux barrier caused by hiatal hernia and transient lower esophageal sphincter relaxations; characterization of the refluxate, particularly of nonacid reflux; prevalence and prognostic value of esophageal dysmotility in GERD; presence and eradication of Helicobacter pylori; Barrett esophagus and extraesophageal manifestations of GERD; and, finally, advances in medical, endoscopic, and surgical treatments of GERD.

Determination of the time of onset of action of ranitidine and famotidine on intra-gastric acidity

BACKGROUND

No standard methods exist for determining the onset of action of gastric antisecretory agents in human subjects.

METHODS

Intragastric pH was measured when placebo, ranitidine 150 mg, ranitidine 75 mg or famotidine 10 mg were administered 30 min after the end of a meal.

RESULTS

When the onset of action was defined as the earliest time that mean gastric pH with active treatment was statistically significantly higher (P < 0.05) than the corresponding placebo value, the onsets of action of ranitidine 75 mg and 150 mg were 55 min, and of famotidine 10 mg, 90 min. When onset was defined in terms of a particular decrease in gastric acid concentration for the group as a whole or for individual subjects, there was an important variation in the relative times of onset of ranitidine 75 mg and famotidine 10 mg.

CONCLUSIONS

When administered after a meal, the onset of action of ranitidine and famotidine on gastric pH can be determined for individual subjects as well as for the group as a whole. When onset was determined for the group using statistical significance, which does not depend on arbitrary cut-off points, ranitidine 75 mg had an earlier onset of action than did famotidine 10 mg.

Integrated acidity and rabeprazole pharmacology

BACKGROUND

Integrated gastric and oesophageal acidity can be calculated from measurements of gastric and oesophageal pH and used to quantify gastric and oesophageal acidity over time. Rabeprazole is a new proton pump inhibitor that is effective in treating gastro-oesophageal reflux disease (GERD).

AIM

To use measurement of integrated gastric and oesophageal acidity to determine the onset, duration and overall effect of rabeprazole in subjects with GERD.

METHODS

Subjects with GERD were required to have oesophageal pH less-than-or-equal 4 for at least 10% of a 24-h recording. Effects of 20 mg rabeprazole on 24-h gastric and oesophageal pH were measured on days 1 and 7 of dosing. Integrated gastric and oesophageal acidity were calculated from time-weighted average hydrogen ion concentrations at each second of the 24-h record.

RESULTS

At steady-state, 20 mg rabeprazole inhibited gastric acidity by 89% and oesophageal acidity by 95%. The first dose of rabeprazole inhibited gastric and oesophageal acidity by at least 70% of the steady-state effect. Oesophageal acidity could be divided into monophasic and biphasic patterns, and rabeprazole had different effects on oesophageal and gastric acidity in these two GERD subpopulations. The onset of action of the first dose of rabeprazole on gastric acidity was 4 h and on oesophageal acidity was 4 h in monophasic subjects and 7 h in biphasic subjects. Integrated acidity was more sensitive than time pH less-than-or-equal 4 in measuring the inhibitory actions of rabeprazole.

CONCLUSIONS

Integrated gastric and oesophageal acidity are quantitative measurements that provide useful and novel information regarding the pathophysiology of GERD as well as the impact of antisecretory agents such as rabeprazole.