Gastric aspiration versus antimony and glass pH electrodes. A simultaneous comparative in vivo study

Evaluation of the effect of orally administered acid suppressants on intragastric pH in cats

Background

Acid suppressant drugs are a mainstay of treatment for cats with gastrointestinal erosion and ulceration. However, clinical studies have not been performed to compare the efficacy of commonly PO administered acid suppressants in cats.

Hypothesis/Objectives

To compare the effect of PO administered famotidine, fractionated omeprazole tablet (fOT), and omeprazole reformulated paste (ORP) on intragastric pH in cats. We hypothesized that both omeprazole formulations would be superior to famotidine and placebo.

Animals

Six healthy adult DSH colony cats.

Methods

Utilizing a randomized, 4‐way crossover design, cats received 0.88–1.26 mg/kg PO q12h fOT, ORP, famotidine, and placebo (lactose capsules). Intragastric pH monitoring was used to continuously record intragastric pH for 96 hours beginning on day 4 of treatment. Plasma omeprazole concentrations at steady state (day 7) were determined by high performance liquid chromatography (HPLC) with ultraviolet detection. Mean percentage time that intragastric pH was ≥3 and ≥4 were compared among groups using ANOVA with a posthoc Tukey‐Kramer test (α = 0.05).

Results

The mean percentage time ± SD that intragastric pH was ≥3 was 68.4 ± 35.0% for fOT, 73.9 ± 23.2% for ORP, 42.8 ± 18.6% for famotidine, and 16.0 ± 14.2% for placebo. Mean ± SD plasma omeprazole concentrations were similar in cats receiving fOT compared to those receiving ORP and in a range associated with acid suppression reported in other studies.

Conclusions and Clinical Importance

These results suggest that both omeprazole formulations provide superior acid suppression in cats compared to famotidine or placebo. Fractionated enteric‐coated OT is an effective acid suppressant despite disruption of the enteric coating.

Effects of ranitidine, famotidine, pantoprazole, and omeprazole on intragastric pH in dogs

OBJECTIVE

To identify the normal gastric acid secretion profile in dogs and determine the degree of gastric acid suppression associated with 4 gastric acid suppressants.

ANIMALS

12 healthy Beagles.

PROCEDURE

Intragastric pH was measured continuously for 24-hour periods with a digital recording system placed via a gastrostomy tube. Baseline measurements were obtained when food was withheld and when dogs were fed a standard diet. Dogs were then treated with ranitidine (2 mg/kg, IV, q 12 h), famotidine (0.5 mg/kg, IV, q 12 h), pantoprazole (1 mg/kg, IV, q 24 h), omeprazole (1 mg/kg, PO, q 24 h), or saline solution for 7 days; intragastric pH was recorded on days 0, 2, and 6. Subsequently, the effects of administering famotidine (0.5 mg/kg, IV, q 8 h; 6 dogs) and omeprazole as a suspension (1 mg/kg, PO, q 12 h; 6 dogs) were evaluated. Median 24-hour intragastric pH, percentage of time pH was > or = 3, and percentage of time pH was > or = 4 were determined.

RESULTS

Median pH, percentage of time pH was > or = 3, and percentage of time pH was > or = 4 were all significantly higher when food was withheld than when dogs were fed. Famotidine, pantoprazole, and omeprazole significantly suppressed gastric acid secretion, compared with saline solution, as determined on the basis of median 24-hour pH and percentages of time pH was > or = 3 or > or = 4. However, ranitidine did not. Omeprazole suspension suppressed gastric acid secretion.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that in healthy dogs, famotidine, pantoprazole, and omeprazole significantly suppress gastric acid secretion. Twice daily administration of a suspension of omeprazole, was the only regimen tested that approached the potential therapeutic efficacy for acid-related disease when assessed by criteria used for human patients.

Glass and antimony electrodes for oesophageal pH monitoring in distressed infants: how different are they?

OBJECTIVE

Although antimony electrodes are by far the most popular for performing oesophageal pH monitoring, there are few data comparing the accuracy of glass and antimony electrodes. Therefore, we tested the accuracy of both electrodes in the prediction of oesophagitis.

METHOD

pH monitoring using a glass electrode and an antimony electrode was performed in 60 distressed infants, aged between 1 and 6 months. An upper endoscopy with oesophageal biopsies was also performed in all infants.

RESULTS

A reflux index (percentage of the total time with pH < 4.0) greater than 5% was considered to be abnormal and was found in 40/60 patients. Histological oesophagitis was present in 26/60 infants. The reflux index was > 5% with the glass electrode in 18/26 children with histological oesophagitis and with the antimony electrode in 10/26 children with histological oesophagitis. Histology of the oesophagus was normal in 22/40 children with abnormal pH monitoring. With the glass electrode, the mean reflux index in the group with oesophagitis was significantly higher than in the group with normal histology, although there was an important overlap. With the antimony electrode, the mean reflux indices in the groups with and without oesophagitis were not different. Regarding normal/abnormal, there was discordance in 35% of the pH studies. No reflux index could be related to a clinically useful sensitivity and specificity to predict oesophagitis.

CONCLUSION

The reflux index does not accurately predict oesophagitis. Oesophageal pH monitoring and endoscopy provide complementary information.

Circadian pattern of intragastric acidity in patients with non-erosive reflux disease (NERD)

BACKGROUND

Most patients with gastro-oesophageal reflux disease have non-erosive reflux disease. Proton pump inhibitors are less effective than expected in these patients, but no previous study has measured their 24-h gastric pH values.

AIMS

To evaluate whether there are differences in 24-h intragastric acidity between reflux patients with and without oesophagitis and controls. The influence of Helicobacter pylori on the gastric pH of reflux patients was also assessed.

METHODS

Sixty-three consecutive patients with gastro-oesophageal reflux disease symptoms who agreed to undergo endoscopy and 24-h pH-metry were recruited. Twenty-five (39%) had erosive oesophagitis and 38 (61%) did not. H. pylori was diagnosed by CLO test, histology and 13C-urea breath test. Gastric pH was also measured in 30 controls without digestive symptoms.

RESULTS

H. pylori was found in seven of the 25 (28%) patients with oesophagitis and 14 of the 38 (37%) patients with non-erosive reflux disease. Oesophageal pH-metry was abnormal in 21 of the 25 (84%) patients with oesophagitis and in 32 of the 38 (84%) patients with non-erosive reflux disease. The median gastric pH did not differ between patients with and without oesophagitis or between them and controls during the 24 h (P = 0.8) and other time intervals (P = 0.2-0.4). The gastric pH did not differ between infected and non-infected patients with oesophagitis (P = 0.2-0.4) or non-erosive reflux disease (P = 0.3-0.8).

CONCLUSIONS

The circadian pattern of intragastric acidity does not differ between patients with non-erosive reflux disease and oesophagitis. Moreover, the study confirms that H. pylori infection does not affect the gastric pH in either group of reflux patients.

Intragastric pH in critically ill neonatal foals and the effect of ranitidine

OBJECTIVE

To characterize intragastric pH profiles in critically ill foals and determine whether administration of ranitidine altered pH profiles.

DESIGN

Prospective observational study.

ANIMALS

23 hospitalized neonatal foals < or = 4 days of age.

PROCEDURE

Intragastric pH was measured continuously for up to 24 hours by use of an indwelling electrode and continuous data recording system. In 21 foals, ranitidine was administered IV.

RESULTS

10 foals had predominantly or exclusively alkaline profiles, 10 had profiles typical of those reported for healthy foals, with periods of acidity (hourly mean pH < 5.0 at least once), and 3 had atypical profiles with periods of acidity. All 10 foals that had intragastric pH profiles typical of healthy foals survived, whereas only 2 foals with alkaline profiles survived, and none of the foals with atypical profiles survived. The effects of ranitidine administration could not be assessed in 13 foals because of a high baseline intragastric pH. In 7 of the remaining 9, ranitidine administration resulted in an alkalinizing response, but this response was often of blunted duration. Ranitidine administration did not appear to alter the intragastric pH profile in the remaining 2 foals.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that hospitalized critically ill foals often have intragastric pH profiles different from those reported for healthy foals and may respond differently to ranitidine administration than do healthy foals. Many critically ill foals have continuously alkaline intragastric pH profiles, questioning the need for prophylactic administration of ranitidine in all critically ill foals.

Comparison of 24-h control of gastric acidity by three different dosages of pantoprazole in patients with duodenal ulcer

BACKGROUND

It is now clear that the extent to which gastric acid secretion must be suppressed varies with the clinical condition being treated.

AIM

To assess the 24-h control of gastric acidity and the individual response variability of three different doses of pantoprazole.

METHODS

Sixty-four duodenal ulcer patients were recruited for this prospective, randomized, multicentre, double-blind, parallel-group study. They were subdivided into three well-matched groups treated with 20 mg o.m., 40 mg o.m. and 40 mg b.d. of pantoprazole, respectively. Endoscopy and intragastric pH monitoring were performed in each patient before and after 14 days of treatment.

RESULTS

Fifty-five patients were eligible for final analysis (17 treated with 20 mg o.m., 18 with 40 mg o.m. and 20 with 40 mg b.d. pantoprazole). The ulcer crater healed in 94, 88 and 95% of cases, respectively. The three dosages of pantoprazole produced significant increases in gastric pH compared to basal levels (P < 0.0001). There was also a clear dose-dependent pharmacodynamic effect, which augmented on moving from the lowest dosage of 20 mg o.m. pantoprazole to the highest dosage of 40 mg b.d. (P < 0.01-0.001). The inter-individual response variability within the three treatment groups was more marked with the dose of 20 mg than with the two higher doses of pantoprazole.

CONCLUSIONS

All three doses of pantoprazole we tested are highly effective in decreasing gastric acidity and there is a clear dose-dependent pharmacodynamic effect on moving from the lowest to the highest dosage. The greatest inter individual variation in the degree of acid inhibition was seen with pantoprazole 20 mg o.m., while the majority of patients responded adequately to the two higher doses of the drug.

Clinical utility of pH paper versus pH meter in the measurement of critical gastric pH in stress ulcer prophylaxis

OBJECTIVE

To evaluate the clinical utility of measuring gastric pH with a pH meter vs. pH paper in critical care patients.

DESIGN

Prospective comparison of gastric pH measurements, using both pH meter and pH paper.

SETTING

Surgical intensive care unit (ICU) at a rural Midwestern university medical center.

PATIENTS

Fifty-one patients who received therapy for prophylaxis of stress ulcers in the surgical ICU.

INTERVENTIONS

Therapy for stress ulcer prophylaxis was monitored.

MEASUREMENTS AND MAIN RESULTS

The pH of 985 gastric samples, taken from 51 patients, was measured with both pH meter and pH paper. The pH meter and pH paper measures demonstrated a concordance correlation coefficient of .896. The mean difference between the two measures (pH paper - pH meter) was estimated to be between -0.4 and 1.4, suggesting a positive bias for the paper. The prevalence of events representing clinically relevant differences between the pH meter and pH paper in the measurement of the same gastric sample was calculated. The frequency with which each of the events occurred consecutively (or, in one case, two nearly consecutive events on the same day) was also calculated. Bias in a clinically relevant range was estimated. A set of "probability profiles" was constructed.

CONCLUSIONS

A hand-held pH meter and pH paper are not interchangeable measures of gastric pH. The pH paper exhibits an appreciable positive bias compared with a hand-held pH meter in the clinically relevant range of 2 to 6. More research is needed to determine if that bias affects treatment outcomes. We recommend the use of a pH meter for patients who demonstrate pH readings of < or = 4, consecutive with readings of < or = 5.

Evaluation of 24-hour gastric acidity in patients with hepatic cirrhosis

BACKGROUND/AIMS

Data from previous studies on gastric acid secretion in patients with hepatic cirrhosis are controversial, due, at least in part, to the possible interference of liver failure and altered gastric mucosal microcirculation on the pharmacological action of the substances used to stimulate the parietal cell. For this reason, we wished to investigate the circadian pattern of gastric acidity by means of continuous 24-hour pH monitoring, which permits measurement of pH fluctuations in a nearly physiological manner and does not require any pharmacological stimulus.

METHODS

Forty-nine patients with liver cirrhosis of different aetiology were recruited for this study. They underwent 24-hour gastric pH-metry with an electrode positioned in the gastric corpus, and their pattern of gastric acidity was compared with that of 49 healthy subjects, matched for age and sex. In a subgroup of 31 patients with cirrhosis, antral pH was recorded in addition to body pH in order to assess whether there are regional differences in gastric acidity.

RESULTS

The circadian, daytime and nocturnal gastric acidity in patients with cirrhosis was significantly lower (p < 0.05-0.001) than that of controls. In the 31 patients studied with two electrodes, antral pH was higher (p < 0.05) than body pH only during the night. The prevalence of Helicobacter pylori infection was rather low (42%) in our patients.

CONCLUSIONS

There is a marked hypoacidity over the circadian cycle in patients with cirrhosis compared to controls, and the greatest difference between them is visible during the nocturnal hours. Also, in patients with liver cirrhosis the pH in the antrum is higher than that in the body of the stomach during the night for reasons that need to be elucidated.

Time pattern of gastric acidity in Barrett's esophagus

Increased gastroesophageal acid reflux is frequently found in patients with Barrett's esophagus, and it has been hypothesized that gastric acid hypersecretion could be an important factor aggravating the exposure of esophageal mucosa to acid and then contributing to the development of this disorder. The aim of the present study was to assess whether the circadian pattern of gastric acidity differs between refluxer patients with and without Barrett's esophagus and normal subjects. Continuous 24-hr gastric pH monitoring was performed in 119 healthy volunteers, 20 patients with Barrett's esophagus, 37 patients with moderate and 10 patients with severe reflux esophagitis without Barrett's esophagus. In all these diseases the final diagnosis was ascertained by means of endoscopy plus biopsy. There was no difference in the 24-hr and daytime patterns of gastric pH between healthy subjects and patients with Barrett's esophagus, while nocturnal acidity was significantly lower (P < 0.05) in the latter population. Gastric acidity, in contrast, was higher (P < 0.05) in controls than in patients with both moderate and severe reflux esophagitis without Barrett's esophagus during the whole 24-hr period. There was no difference between refluxer patients with and without Barrett's esophagus in any of the three time intervals we analyzed. Because normal subjects had lower gastric pH than patients with Barrett's esophagus during the night and than patients with reflux esophagitis during the whole 24-hr period, gastric hyperacidity is not a relevant factor in the development of both metaplastic columnar epithelium and inflammatory changes in the distal esophagus, and other pathophysiological mechanisms are involved in these histological alterations.

Are duodenal ulcer seasonal fluctuations paralleled by seasonal changes in 24-hour gastric acidity and Helicobacter pylori infection?

The occurrence of duodenal ulcer is characterized by seasonal variation, for poorly understood reasons. No previous study has assessed whether 24-h intragastric acidity and Helicobacter pylori infection have similar seasonal fluctuations in patients with this disorder. For this reason, we evaluated retrospectively the circadian gastric pH in 319 new patients (226 men and 93 women, mean age 45.2 years) with endoscopically proven duodenal ulcer, who agreed to undergo this examination during the years 1987-1992 in our center. The month-by-month occurrence of the disease over the global 6-year period was assessed, and the mean pH values were calculated for each patient during three time intervals of interest: 24 h, daytime (08:00-19:59 h), and nighttime (20:00-07:59 h). The mean pH values of these three time periods were then calculated month by month throughout the annual cycle. H. pylori infection was sought by histology in 171 patients examined in the period from 1990 to 1992. The percentage of H. pylori-positive duodenal ulcer patients was then calculated for each season. The calendar fluctuation of duodenal ulcer occurrence showed an evident increase (p < 0.001) in fall (October-December) and in winter (January-March) compared with spring (April-June) and summer (July-September). Both 24-h and nighttime gastric acidity showed no significant variation by month, whereas daytime gastric pH varied significantly (p < 0.05) with two evident decreases, meaning higher acidity, in April and August. H. pylori infection was detected in 152 of 171 patients (89%), and the percentage of H. pylori-positive duodenal ulcers did not differ from season to season. We conclude that there was no parallel circannual fluctuation of duodenal ulcer, gastric acidity, and H. pylori infection in the restricted sample of patients we studied. This reduces the apparent relevance of acid in inducing ulcer seasonal fluctuation. Also, the responsibility of H. pylori in this phenomenon can be excluded until a reliable diagnostic method capable of distinguishing recent from old infection is found.

Assessment of gastric acidity in intensive care patients: intermittent pH registration cannot replace continuous pH monitoring

OBJECTIVE

To test the accuracy of colour-scaled indicator papers to measure pH values and to study the correlation between this method of measuring gastric juice pH once daily and 24-h continuous intragastric pH monitoring in intensive care patients.

DESIGN

The accuracy of indicator papers was tested in the laboratory using colourless solutions and aspirated gastric juice and was then verified with a laboratory pH meter. Continuous intragastric pH monitoring was performed in mechanically ventilated ICU patients. Percentages of time with a pH value <3.0 and median pH values by 24-h continuous intragastric pH monitoring were compared to pH values measured once daily with indicator paper.

SETTING

A mixed ICU.

PATIENTS

A total of 150 measurements were taken by continuous pH monitoring in 91 mechanically ventilated ICU patients.

MEASUREMENTS AND RESULTS

The correlation between the pH measured with the indicator paper and subsequently verified with a laboratory pH meter in colourless solutions was 0.96 [regression coefficient (RC) 0.98, 95% confidence interval (CI) 0.91-1.05]. Measured in gastric juice it was 0.95 (RC 0.95, 95% CI 0.88-1.01). The correlation between median pH values, determined with 24-h continuous intragastric pH monitoring, and values measured with indicator papers was 0.39 (RC 0.43, 95% CI 0.26-0.59). The mean difference in pH, as determined by the analysis of Bland and Altman], was 0.9 with a SD of 4.7. The correlation between the percentage of time with pH < 3.0, as obtained with continuous registration, and median gastric pH values (also obtained with continuous registration) was -0.94 (RC-0.06, 95% CI-0.06- -0.05); the correlation between the time and gastric pH values (measured with indicator paper) was-0.40 (RC-0.02, 95% CI-0.03- -0.02).

CONCLUSION

The colour-scaled indicator paper is an accurate method of measuring pH values, but there is a poor correlation between gastric pH values measured once daily and a total measurement derived from 24-h continuous intragastric pH monitoring. Changes in intragastric pH values cannot be accurately studied when measuring acidity once daily. The influence of various treatment regimens on intragastric acidity in relation to the development of gastric colonization and nosocomial pneumonia should be investigated either with continuous intragastric monitoring or with frequent measurements in aspirated gastric juice.

Gastric emptying of two radiolabelled antacids with simultaneous monitoring of gastric pH

The aim of this study was to assess the gastric emptying rate of two antacids using an scintigraphic technique and simultaneous monitoring of gastric pH in 16 healthy male volunteers. Ten ml of Talcid (hydrotalcite 1 g) and Maalox (Mg-Al-hydroxide), with a similar neutralization capacity, were labelled with technetium-99m using a pyrophosphate bridge. Labelled antacids were given on separate days (within 2 weeks), 1 h after a standard meal. Intragastric pH was measured for at least 4 h, using ambulatory pH-metry with a dual-crystant antimony catheter. Continuous monitoring was started 1 h prior to the meal (baseline) and lasted 3 h (post-prandial, post-antacid and final periods). The antacid capacity of labelled and unlabelled antacids was similar. The mean percentages of antacids retained in the stomach fitted a linear model. The mean half-emptying time of Talcid was 63.9 +/- 27.9 min, while that of Maalox was 57.3 +/- 23.9 min (P = NS). The recordings of gastric pH (mean values of pH for each period) showed a similar profile for both antacids. The mean pH (Maalox vs Talcid) was 1.69 vs 2.07 in the baseline period, 1.95 vs 1.93 in the post-prandial period, 1.79 vs 1.15 in the post-antacid period (P = NS) and 0.4 vs 0.52 in the final period (P < 0.05 vs prior periods). In conclusion, the gastric emptying of Talcid and Maalox was similar and pH profiles were parallel and remained unchanged for the two antacids within the first hour of intake. A significant decrease in pH was observed 1 h after intake of the antacids, suggesting a possible rebound effect.

The knee-elbow position relieves distension

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Antisecretory effects of three omeprazole regimens for maintenance treatment in duodenal ulcer

This study was carried out to assess the antisecretory effects and their possible changes over time of three different dose regimens of omeprazole that could be proposed for maintenance treatment in duodenal ulcer. Forty-five patients with endoscopically proven duodenal ulcer were studied by means of 24-hr gastric pH-metry both in basal conditions and on the fifth day of acute treatment with omeprazole 20 mg in the morning. Ulcers healed after four weeks (in three cases after eight weeks) and afterwards, 15 patients were randomized to receive orally at 0800 hr in single-blind fashion omeprazole 10 mg daily (group A), 15 to receive omeprazole 40 mg on Saturday and Sunday followed by a five-day period without medication (group B), and 15 to receive omeprazole 20 mg every other day (group C) for up to three months. On the 20th and 80th days of these maintenance treatments 24-hr gastric pH-metry was repeated to assess the antisecretory effectiveness of each regimen over a two-month period. In patients of group B these tests began at 1700 hr on Friday, the last of five days off treatment, and in those of group C at 1700 hr of the day off medication. All three dose regimens of omeprazole were able to raise pH values significantly (P < 0.01-0.001) compared to basal levels. Omeprazole 20 mg every other day was more effective (P < 0.01) than omeprazole 40 mg weekend, but did not differ significantly from omeprazole 10 mg daily. The durations of acid inhibition (pH > 3.0 units/24 hr) were 12.44, 10.00, and 17.38 hr with groups A, B, and C, respectively. There was no significant difference between the pH profiles of the 20th and 80th days with every dose regimen. It is concluded that all three dose regimens of omeprazole are effective in reducing gastric acidity and their pharmacodynamic action does not change with time. Therefore they are suitable to be assessed in large clinical trials aimed at verifying the prevention of duodenal ulcer recurrence for longer periods.

New method for improving accuracy of 24-hour continuous intragastric pH-metry. Reflections on physiological and pharmacological studies

Continuous 24-hr intragastric pH-metry was prospectively performed in 801 subjects with different clinical conditions using two pH electrodes placed closely adjacent. The aim was to assess the in situ repeatability of the test and to verify whether the removal of artifacts, interference, and noise usually superimposed onto the fundamental signal recorded by the measuring apparatus improves the clinical usefulness of experimental data. The following debugging/filtering procedure was used: first, pH recordings of each channel were amended separately from artifacts, then they underwent 7 min windowed median interference debugging, and finally Wiener noise filtering was applied. Afterwards, the 24-hr mean pH profile was obtained in each subject by averaging the pH tracings of the two channels every minute (1440 data points/24 hr). The efficiency of this procedure was assessed at each step by evaluating the difference among groups using the O'Brien test, a distribution-free nonparametric method well-suited for evaluating differences among groups allocated onto a two-way layout. The differences among groups calculated from raw pH data of the single channels can be very misleading, in that it is possible to find that they are significant on one channel and not significant on the other channel. Conversely, the significance of the differences among groups increases progressively at each step of the above debugging/filtering procedure applied to raw pH profiles of each channel. Seven minutes was shown to be the most suitable time lag for windowed median removal of interference.(ABSTRACT TRUNCATED AT 250 WORDS)

A pharmacodynamic study of two omeprazole regimens suitable for long-term treatment of duodenal ulcer

BACKGROUND

The experience with long-term treatment of peptic ulcer with omeprazole is still scant, but the possibility cannot be excluded that its better pharmacodynamic effect on gastric acidity also has a positive result in the relapse rate. Moreover, this drug acts via a mechanism other than receptorial binding, and therefore its efficacy should not dissipate with time. This study was carried out to assess the pharmacodynamic properties and the possible changes with time of two dose regimens of omeprazole that could be suitable for long-term treatment in duodenal ulcer.

METHODS

Twenty patients with endoscopically proven duodenal ulcer were studied by means of 24-h gastric pH-metry both in basal conditions and on the 5th day of acute treatment with 40 mg omeprazole in the morning. All the ulcers healed after 4 weeks, and thereafter 10 patients were randomized to receive orally 20 mg omeprazole daily at 0800 h in single-blind fashion (group A) and 10 to receive 20 mg omeprazole every other day (group B) for up to 6 months. At the end of the 1st, 3rd, and 6th month of these maintenance treatments 24-h gastric pH-metry was repeated to assess the antisecretory effect of each regimen over time. In group-B patients the test was performed on 2 consecutive days (without and with medication) at each time interval. The fasting gastrin values were also determined. The patients underwent esophagogastroduodenoscopy every 2 months.

RESULTS

Three patients in group B were lost to follow-up for various reasons, and only seven remained eligible for final analysis. The two long-term regimens of omeprazole were able to increase significantly pH values (p < 0.02-0.001) and the times spent at and above pH 3.0 (p < 0.001) over 24 h compared with basal conditions. In group A the 24-h pH value obtained in the 6th month was higher (p < 0.02) than that in the 3rd month of maintenance treatment. In group B the pharmacologic effect tended to decrease on the day without medication compared with the day with medication, but the difference between them was significantly (p < 0.05) only at the 6-month interval. There was no significant difference between the gastrin levels of the two groups in the long-term treatment. No ulcer relapse was detected at any long-term endoscopic control in the two groups of patients.

CONCLUSIONS

The two omeprazole regimens we tested are effective in reducing gastric acidity, and their pharmacodynamic action does not decrease with time. They are therefore suitable for maintenance treatment in acid-related disorders.

Laboratory medicine in ulcer disease

The role of laboratory medicine in ulcer disease is poorly defined. However there is increasing evidence of the clinical usefulness of some laboratory tests that investigate secretory functions and defensive properties of the stomach, gastrointestinal hormones and Helicobacter pylori infection. These tests may modify the clinical management of patients with peptic ulcer by identifying H. pylori positive subjects, patients with high acid output, patients who do not respond to antisecretory therapy, and patients with high gastrin levels in whom Zollinger-Ellison syndrome may be suspected. Here we review the clinical value of laboratory tests in ulcer disease, particularly as concerns the cost/benefit ratio. The relative merits of these tests are described giving an indication of their possible role in the diagnostic algorithm.

Bolus infusion of famotidine: effects on gastric pH by repeated 12-hour doses of 20 mg in postoperative patients

This study was carried out to assess the efficacy of intravenous (IV) famotidine in suppressing gastric secretion over a 48-hour period. Twenty postoperative patients requiring a nasogastric tube received famotidine 20 mg IV every 12 hours and gastric pH was measured continuously by means of an indwelling probe. A baseline recording was performed over the first 4 hours and then the drug was infused every 12 hours (q12h) over a 15-minute period for the subsequent 48 hours. The mean pH value achieved during each time segment under active treatment was significantly higher (P < .001) than the mean basal value. Also the density distributions of minutes spent at the various pH units confirm that famotidine is highly effective (P < .001) in raising and maintaining gastric pH above 4.0 units during most of the drug-related period (44 hours). It can be concluded that repeated intravenous boli of famotidine 20 mg every 12 hours allow us to obtain an effective control of intragastric acidity. The antisecretory action is consistent over the total 48-hour period examined and therefore the use of intermittent infusion of famotidine seems to be advisable, as opposed to the recommended continuous IV administration of cimetidine and ranitidine. There is, however, a considerable intersubject variability in the antisecretory response to the drug.

Variability in individual response to various doses of omeprazole. Implications for antiulcer therapy

This study was carried out in order to perform a combined prospective assessment of the individual pharmacodynamic response and of duodenal ulcer healing in patients treated with three different doses of omeprazole. Ninety-nine patients with endoscopically proven duodenal ulcers were subdivided into three parallel groups of 33 cases, who were randomly assigned to receive orally at 0800 hr, in single blind fashion, either 10 mg, 20 mg, or 40 mg of omeprazole. All of them underwent continuous intragastric pH monitoring both in basal conditions and on the fifth day of each dose regimen; ulcer healing was then assessed endoscopically after four weeks of treatment. All three doses of omeprazole caused pH values to increase significantly (P < 0.001) over the whole 24-hr period. In patients treated with omeprazole 10 mg, the individual responses showed the highest variability: the acid inhibition, expressed in terms of time spent above pH 3.0, lasted for more than 16 hr in 42% of cases, for more than 8 hr in 28%, and for less than 6 hr in 30%. In patients treated with omeprazole 20 mg, the pharmacological response was more marked and uniform and lasted for more than 16 hr in 79% of cases; however, it is worth noting it lasted for less than 6 hr in three patients (10%). In patients treated with omeprazole 40 mg, the individual response was excellent (more than 16 hr) in 94% of cases, and it lasted for less than 6 hr in only one patient (3%).(ABSTRACT TRUNCATED AT 250 WORDS)

Circadian acidity pattern in prepyloric ulcers: a comparison with normal subjects and duodenal ulcer patients

We used continuous 24-h pH monitoring to compare the circadian intragastric acidity of 36 patients with prepyloric ulcers (PPU) with that of 101 normal subjects (NS) and that of 206 patients with duodenal ulcer (DU). The ulcer crater was endoscopically ascertained in all cases, and PPU were located within an area up to 2 cm proximal to the pylorus. The pH curve pertaining to DU patients ran below that of NS during most of the circadian period, whereas the pH profile of PPU patients was higher than that of NS, and this was particularly true during the evening and the night. The acidity of PPU patients was significantly lower (p < 0.01) than that of NS during the night only, whereas it was lower (p < 0.05-0.001) than that of DU patients during each time interval analysed (24 h, nighttime, and daytime). Our findings show that the gastric acidity of PPU patients differs greatly from that of DU patients, since it is lower throughout the whole 24-h period, and particularly during the night. Thus these two entities are pathophysiologically different with regard to the acidity pattern and should be considered two distinct subgroups of peptic ulcer disease instead of being incorporated, as usually happens, in the clinical group 'duodenal ulcer disease'.

Twenty-four-hour control of gastric acidity by twice-daily doses of placebo, nizatidine 150 mg, nizatidine 300 mg, and ranitidine 300 mg

This study was carried out to assess the effects on gastric acidity of placebo twice daily (bid), nizatidine 150 mg bid, nizatidine 300 mg bid, and ranitidine 300 mg bid by means of continuous 24-hour intragastric pH monitoring. Twelve patients with duodenal ulcer in remission were randomized to receive in single-blind fashion the above medications on four separate occasions, at least 1 week apart. The three active regimens produced higher pH values (P < .001) and maintained gastric pH above 3.0 units for a longer period (P < .001) than placebo in all time intervals but evening. Nizatidine 150 mg bid caused a lower rise in pH than nizatidine 300 mg bid (P < .01) and ranitidine 300 mg bid (P < .05) during both the daytime and the whole 24 hours. In these time windows also the time spent above 3.0 pH units was significantly shorter for the former regimen than for 300 mg bid of both nizatidine (P < .01) and ranitidine (P < .05). There was no difference between the latter two dosing schedules in terms of both potency and duration of action in all the time intervals considered. It is concluded that twice daily doses of H2 blockers are more effective than placebo in reducing gastric acidity. Three hundred milligrams twice daily of both nizatidine and ranitidine produce a significantly greater and longer-lasting acid suppression than 150 mg bid of nizatidine. Our study also confirms the greater effectiveness of H2 antagonists during nighttime than during day-time.

Comparison of low-dose antacids, cimetidine, and placebo on 24-hour intragastric acidity in healthy volunteers

Low-dose aluminium (Al) antacids are effective in promoting ulcer healing and symptomatic relief in peptic ulcer patients, although the effect on intragastric acidity is very weak. In this randomized, double-blind study, 24-hr intragastric acidity was compared in 11 healthy volunteers, treated with a low-dose Al antacid regimen (1 tablet four times a day), cimetidine (800 mg at bedtime) and placebo, using the double-dummy technique. Standardized meals were given at 8 AM, noon, and 5 PM. Medication was given 1 hr after meals and at bedtime. Intragastric acidity was recorded with a nasogastric monocrystant antimony pH catheter, connected to an ambulatory digital data recorder. No significant difference in intragastric acidity was observed between antacid and placebo treatment. Treatment with cimetidine reduced circadian and nocturnal (but not diurnal) intragastric acidity significantly, as compared to both placebo and antacid treatment. The results support the hypothesis that Al antacids promote peptic ulcer healing by other mechanisms than acid neutralization.

Gastric acidity and gastroesophageal reflux patterns in patients with esophagitis

Esophageal pH-metry is the test of choice for diagnosing gastroesophageal reflux. However, although it allows acid refluxes to be distinguished, it is of limited value for identifying alkaline or mixed (acid mixed with alkaline material) refluxes. To evaluate the ability of dual pH-metry to identify alkaline or mixed refluxes, the gastric acidity and gastroesophageal reflux pattern were evaluated simultaneously in 64 patients with mild-moderate esophagitis, in 28 patients with severe or complicated esophagitis, and in 20 healthy subjects. A dual esophageal gastric pH-probe allowed three different types of esophageal reflux to be distinguished: (a) acid refluxes, defined as a drop in esophageal pH to values less than 4 together with a gastric pH less than 4; (b) mixed refluxes, defined as a drop in esophageal pH from baseline to values greater than 4 associated with rises in gastric pH to greater than 4 values; (c) alkaline refluxes, defined as a rise in esophageal pH to greater than 7 associated with a simultaneous increase in gastric pH to greater than 4. Gastric acidity was more significantly reduced in patients with severe or complicated esophagitis than it was in healthy subjects (P less than 0.01). The reflux pattern in both mild-moderate and severe esophagitis was characterized by mainly acid refluxes and a marked increase in the time the esophagus mucosa was exposed to acid (P less than 0.001). Pure alkaline refluxes were rare (less than 1%) in both healthy subjects and esophagitis patients. The number of mixed refluxes was considerably higher in severe esophagitis patients than it was in either mild-moderate esophagitis patients or controls (P less than 0.05). The finding of mixed refluxes in severe or complicated esophagitis suggests that biliary acids and/or pancreatic enzymes are involved in the pathogenesis of severe forms of esophagitis.

Antimony and glass pH electrodes can be used interchangeably in 24-hour studies of gastric acidity

Antimony and glass pH electrodes show almost identical experimental errors in continuously measuring buffer solutions at constant temperature over 24 hr. These errors are lower than the nominal quantization error of the instruments and are not properly described by the 24-hr drift determination. The addition of food particles to the solutions can induce severe reading artifacts. The longer response time reported in vitro of antimony electrodes when moving from pH 1 to pH 7 (3.4 sec vs 0.8 sec with glass electrodes) is irrelevant during in vivo pH-metry studies, because we found that the greatest absolute difference between raw fast acquired (4-6 sec) consecutive pH readings of two commonly used devices was 0.7 pH units in circadian profiles obtained from 413 subjects with various clinical conditions. In our in vivo studies, gastric acidity was monitored continuously with two side-by-side minielectrodes, which were variously combined (antimony-glass, A-G; antimony-antimony A1-A2; glass-glass, G1-G2) and applied on groups of 27 subjects matched for clinical condition. The 24-hr pH means and the 24-hr [H+] means calculated from the acidity profiles obtained with the three electrode combinations, lie on the identity line in each group. Using the Bland-Altman technique for assessing measurement agreement, the differences between the 24-hr pH means and the 24-hr [H+] means obtained with the three combined systems are similar (P = .903 and P = 0.824, respectively) and their 95% confidence limits are comprised within the range (+/-) of the reading error of the measuring systems (namely, +/- 0.3 pH units and +/- 12 mmol/liter in terms of [H+]).(ABSTRACT TRUNCATED AT 250 WORDS)

Inaccuracy of hourly sampled pH measurements in describing the effect of antisecretory drugs on circadian gastric acidity

This study was carried out in order to verify whether gastric pH measurements obtained with continuous monitoring are more accurate in assessing the pharmacodynamic properties of antisecretory drugs than those obtained with the traditional hourly nasogastric aspiration method. Accordingly, we compared the most commonly used acidity indexes (median of pHs and mean of [H+]s) and the total circadian time spent above 4.0 pH units, all of which were calculated from both raw data sampled at rates of a few seconds with modern apparatus and data obtained from the same profiles scanned punctually at a 60 minute rate. The analysis referred to 231 continuous gastric pH-metries which were performed over the circadian period to evaluate the acid inhibitory effects of different doses and dosage regimens of various H2-antagonists. In the population as a whole, the numbers and percentages of subjects, whose 60-minute sampled medians of pHs and means of [H+]s differed by less than +/- 10% from those obtained from raw fast-acquired data, were 107 (46%) and 34 (15%), respectively. There was even less agreement in the case of the circadian time above 4.0 pH units (26 cases = 11%). No statistical difference (P = .7) between the concordance rates of each variable in the three groups was observed. Considered simultaneously, there was concordance of the above three indexes in only seven out of the 231 cases. These results show that the hourly sampling rate fails to represent adequately gastric acidity changes induced by antisecretory drugs, due to the scarcity of experimental points. The acidity indexes calculated from these slowly sampled data are inaccurate, especially when the means of [H+]s are considered, and the duration of action of the drug often is defined randomly.

Clinical relevance of sampling rate in the characterization and analysis of 24-hour gastric acidity. A report on 413 cases

Four hundred and thirteen continuous, high-frequency-sampled gastric pH-metries were subdivided into six groups (normal subjects and patients with duodenal ulcer, gastric ulcer, chronic gastritis, prior cholecystectomy, or antisecretory treatment). The frequency distribution of those pH fluctuations that were greater than the quantitation error of instruments did not differ significantly (p greater than 0.30) between groups. Five per cent of these real pH fluctuations lasted less than 3 min. As the sampling rate increased from 1 to 60 min, the percentage of subjects whose 24-h median of pHs differed by no more than +/- 10% from that calculated on the raw high-frequency-acquired data progressively decreased (99.8%-42%). This error propagation was more marked in the case of [H+] integrals (99%-10%). A sampling rate equal to or faster than 1 min is necessary to provide a proper representation of the circadian pH pattern and to calculate accurate acidity indexes, regardless of the physiologic or pharmacologic nature of the profile.

Low bedtime doses of H2-receptor antagonists for acute treatment of duodenal ulcer

Twenty-four-hour intragastric acidity was measured continuously over five separate occasions in 15 patients with healed duodenal ulcers. They were randomized to receive either placebo, cimetidine 800 mg, ranitidine 150 mg, famotidine 20 mg, or nizatidine 150 mg, given at 2200 hr in double-blind fashion. All H2-receptor blockers were more effective than placebo in suppressing both circadian (P less than 0.05-P less than 0.01) and nocturnal (P less than 0.002) gastric acidity, while there was no significant differences between the effects of the four active drugs in the same time periods. The percentage of nocturnal acid inhibition (2300-0800 hr) over placebo in terms of H+ values was virtually 100% with all active treatments. The effect on daytime (0800-1700 hr) and evening (1700-2300 hr) acidity of both placebo and the four H2-receptor antagonists was similar. Therefore, in the above doses H2-receptor blockers guarantee overnight anacidity to a similar degree and cause the physiological buffering of daily meals on gastric acidity to be fully exploited. Furthermore, the reducing effect of daily meals on drug action can be prevented. Since strong acid suppression strictly confined to the nocturnal period has been shown to be closely correlated with the highest ulcer healing rates, it is suggested that single low bedtime doses of H2-receptor antagonist should be evaluated in the acute treatment of duodenal ulcer.