Relationship between reduction of gastric acid secretion and plasma gastrin concentration during omeprazole treatment

Omeprazole Reduces Calcium Digestibility in Thoroughbred Horses

Proton pump inhibitors such as omeprazole reduce nutrient digestibility in humans. This study determined the effect of omeprazole on the digestibility of diets containing limestone or marine-derived calcium (BMC) and to assess changes in blood parameters associated with gastric acid production and calcium status in horses. Thoroughbreds were used to evaluate the digestibility of diets containing different calcium sources with or without omeprazole over four 21-day periods. Each 21-day period had a 15-day diet adaptation phase followed by a 6-day collection phase, consisting of a 5-day total fecal collection period and a final day for gastroscopy and blood sampling. Horses were fed the same diet with either 60 g/d BMC or 50 g/d limestone, so the total diet provided ∼45 g calcium. Horses on omeprazole were given GastroGard once daily for the final 14 day of each 21-day period, which supplied 3.91 ± 0.17 mg/kg BW/d of omeprazole. On day 21, blood samples were taken and gastric fluid pH was measured 8 hour after omeprazole administration. Omeprazole had a profound effect on gastric fluid pH in omeprazole-treated horses compared with nontreated horses. Serum gastrin doubled in omeprazole-treated horses compared with nontreated horses. Omeprazole and calcium source did not affect digestibility of phosphorus, magnesium, potassium, sodium, iron, copper, zinc, or manganese but did affect calcium digestibility. Omeprazole reduced apparent calcium digestibility from 52.0% to 41.4% in limestone and from 55.1% to 46.5% in BMC, equalling a 20.3% and 15.6% decrease in calcium digestibility in the limestone and BMC, respectively. Mineral source had a significant effect on calcium digestibility with BMC at 50.8% and limestone at 46.7%.

Chronic proton pump inihibitor therapy and calcium metabolism

Proton pump inhibitors (PPIs) have been widely used since their introduction in the late 1980s because they are highly effective for acid-related conditions. However, some recent epidemiological studies have suggested a positive association between PPI therapy and the risk of osteoporotic fractures. The potential mechanisms underlying this association may be related to the physiologic effects of chronic acid suppression on calcium metabolism. First, chronic hypergastrinemia induced by PPI therapy may lead to parathyroid hyperplasia, resulting in increased loss of calcium from the bone. Second, profound gastric acid suppression may reduce the bioavailability of calcium for intestinal absorption. I will review the published evidence regarding these potential links and discuss their clinical implications.

Rebound acid hypersecretion after withdrawal of gastric acid suppressing drugs: new evidence of similitude

BACKGROUND

Homeopathy is based on the principle of similitude (similia similibus curentur) using medicines that cause effects similar to the symptoms of disease in order to stimulate the reaction of the organism. Such vital, homeostatic or paradoxical reaction of the organism is closely related to rebound effect of drugs.

METHOD

Review of the literature concerning the rebound effects of drugs used to suppress gastric acidity, particularly proton pump inhibitors (PPIs).

RESULTS

The mechanism of action of these effects is discussed. Rebound in terms of clinical symptoms and physiological effects occur in about 40% of people taking PPIs, their timing depends on the half-life of the drug and the adaptation period of the physiological mechanisms involved. The wide use of PPIs may be linked to the rising incidence of carcinoid tumours.

CONCLUSIONS

These findings support Hahnemann's concept of secondary action of drugs. We are developing a homeopathic materia medica and repertory of modern drugs on the basis of reported rebound effects.

PREDICTING EFFICACY OF PROTON PUMP INHIBITORS IN REGULATING GASTRIC ACID SECRETION

Developing drugs to treat gastric acid related illnesses such as ulcers and acid reflux disease is the leading focus of pharmaceutical companies. In fact, expenditure for treating these disorders is highest among all illnesses in the US. Over the last few decades, a class of drugs known as a proton pump inhibitors (PPIs) appeared on the market and are highly effective at abating gastric illnesses by raising stomach pH (reducing gastric acid levels). While much is known about the action of PPIs , there are still open questions regarding their efficacy, dosing and long-term effects. Here we extend a previous gastric acid secretion model developed by our group to incorporate a pharmacodynamic/pharmacokinetic model to study proton pump inhibitor (PPI) action. Model-relevant parameters for specific drugs such as omeprazole (OPZ) , lansoprazole (LPZ) and pantoprazole (PPZ) were used from published data, and we conducted simulations to study various aspects of PPI treatment. Clinical data suggests that duration of acid suppression is dependent on proton pump turnover rates and this is supported by our model. We found the order of efficacy of the different PPIs to be OPZ>PPZ>LPZ for clinically recommended dose values, and OPZ>PPZ=LPZ for equal doses. Our results indicate that a breakfast dose for once-daily dosing regimens and a breakfast-lunch dose for twice-daily dosing regimens is recommended. Simulation of other gastric disorders using our model provides atypical applications for the study of drug treatment on homeostatic systems and identification of potential side-effects.

Acid inhibition and the acid rebound effect

Acid secretion from gastric parietal cells is a result of a complex interaction between different stimulatory and inhibitory mediators. One of the most important mediators is gastrin, which stimulates gastric acid secretion from parietal cells mostly indirectly, by the release of histamine from enterochromaffin-like (ECL) cells. Therapy with antisecretory agents leads to hypergastrinemia, mucosal hyperplasia and increased ECL cell mass, which results in increase of gastric acid secretion capacity. This increased secretion capacity has been shown to manifest itself after antisecretory therapy withdrawal as rebound acid hypersecretion (RAH). Various studies have quantified acid hypersecretion after the cessation of therapy with H(2) antagonists and proton-pump inhibitors (PPIs). While most of those studies had small patient numbers, the findings generally demonstrate that RAH after H(2) antagonist therapy is of low magnitude, short duration, and has questionable clinical significance. On the contrary, acid hypersecretion after PPI therapy is more pronounced, lasts longer, and could possibly be the cause of acid-related symptoms. Potential for causing symptoms has recently been confirmed in two randomized placebo-controlled studies, and while we witness the increasing use of PPIs, RAH could become a proven cause of failure to withdraw therapy in a proportion of patients with reflux or dyspeptic symptoms.

Proton pump inhibitors and rebound acid hypersecretion

Rebound acid hypersecretion is defined as an increase in gastric acid secretion above pre-treatment levels after cessation of antisecretory therapy. Proton pump inhibitors (PPIs) have been proved to be more effective than histamine-2 receptor antagonists in suppressing intragastric acidity and have therefore become the main choice for management of acid-related complaints. Recent studies have shown that PPI therapy-elicited rebound acid hypersecretion could in turn induce acid-related symptoms. This makes it difficult for patients to cease PPI therapy. Hypergastrinemia is an important mechanism that leads to rebound acid hypersecretion. To reduce the occurrence of rebound acid hypersecretion, efforts should be made to restrict indications for using PPIs.

Rebound acid hypersecretion from a physiological, pathophysiological and clinical viewpoint

OBJECTIVE

The recent description of dyspepsia in healthy individuals after stopping treatment with proton-pump inhibitors (PPIs) indicates that reflux disease may worsen due to this treatment. The aim of this paper is to review current knowledge of the regulation of gastric acid secretion, including maximal acid secretion, and to improve understanding of the pathogenesis of acid-related conditions.

MATERIAL AND METHODS

We reviewed our findings from three decades of studies on gastric acid secretion in the isolated rat stomach and in humans as well as studies by the group of Robert Jensen involving gastrinoma patients.

RESULTS

The parietal cell has receptors for histamine and acetylcholine, whereas the gastrin receptor is localized to the enterochromaffin-like (ECL) cell. Gastrin-stimulated histamine release depends on the ECL cell mass, which is regulated by gastrin. The parietal cell mass is also influenced by gastrin. All conditions with hypergastrinemia concomitant with a normal oxyntic mucosa result in an increase in acid secretion. Helicobacter pylori infection in the antral mucosa may induce duodenal ulcers by its effect on acid secretion, as in patients with gastrinoma. Whereas PPIs induce clinically important rebound acid hypersecretion, histamine-2 blockers do not, since they also induce tolerance.

CONCLUSION

From a biological and physiological point of view, patients should be given treatment that disturbs the normal physiology as little as possible.

The production and role of gastrin-17 and gastrin-17-gly in gastrointestinal cancers

The gastrointestinal peptide hormone gastrin is responsible for initiating the release of gastric acid in the stomach in response to the presence of food and/or humoral factors such as gastrin releasing peptide. However, it has a role in the growth and maintenance of the gastric epithelium, and has been implicated in the formation and growth of gastric cancers. Hypergastrinemia resulting from atrophic gastritis and pernicious anemia leads to hyperplasia and carcinoid formation in rats, and contributes to tumor formation in humans. Additionally, gastrin has been suspected to play a role in the formation and growth of cancers of the colon, but recent studies have instead implicated gastrin processing intermediates, such as gastrin-17-Gly, acting upon a putative, non-cholecystokinin receptor. This review summarizes the production and chemical structures of gastrin and of the processing intermediate gastrin-17-Gly, as well as their activities in the gastrointestinal tract, particularly the promotion of colon cancers.

Effects of dexlansoprazole MR, a novel dual delayed release formulation of a proton pump inhibitor, on plasma gastrin levels in healthy subjects

Dexlansoprazole MR is a modified release formulation of a proton pump inhibitor being developed for the treatment of acid-related disorders. The purpose of this study is to characterize the plasma gastrin (PG) profile associated with administration of dexlansoprazole MR. Forty-two healthy subjects receive dexlansoprazole MR 90 mg, dexlansoprazole MR 120 mg, and lansoprazole 30 mg once daily for 5 days in a randomized, open-label, 3-period crossover study with at least 14-day washout intervals. Twenty-four-hour PG profiles are obtained at baseline (day -1 of period 1) and on days 1 and 5 in each period. Fasting PG levels are determined on days 8 and 12 in periods 1 and 2. On day 1, 24-hour PG levels increase from baseline to a similar extent with all regimens. On day 5, 24-hour PG levels with both dexlansoprazole MR regimens increase further and to a similar extent and are slightly higher than PG levels with lansoprazole. For all regimens, fasting PG levels on days 5 and 6 are higher than baseline levels (P<.05) and start to decrease by day 8, returning to near baseline at day 12. In this study, dexlansoprazole MR administration results in moderate increases in PG, similar to lansoprazole, which return to baseline levels within 7 days post dosing.

Long-term use of proton pump inhibitors does not affect the frequency, growth, or histologic characteristics of colon adenomas

BACKGROUND

The clinical significance of the trophic effects of long-term proton pump inhibitors (PPI)-related hypergastrinemia on colon polyps remains unknown.

AIM

To study the frequency, growth, and histology of colon polyps in patients on chronic PPI therapy (cases), compared to those not receiving acid suppression (controls).

METHODS

Medical records of 2868 consecutive patients who underwent two or more colonoscopies, performed 3 or more months apart were reviewed. Cases (116) that used PPIs between the two colonoscopies were then compared to controls (194).

RESULTS

Demographics and risk factors for colon cancer were comparable between the two groups. At baseline the mean frequency and size of adenomatous polyps were similar in cases and controls (P > 0.05) and at follow-up, these were 0.89 and 1.18 (P > 0.05; 95% CI of -0.08 to 0.66) and 4.09 mm and 4.00 mm (P > 0.05; 95% CI -2.29 to 2.11), respectively with no significant change. However, control group had a higher mean frequency and size of hyperplastic polyps at baseline as well as at follow-up colonoscopy (P < 0.05).

CONCLUSIONS

The long-term use of PPI does not influence the frequency, growth, or histology of adenomatous polyps, but is associated with a reduction in both baseline and interval development of hyperplastic polyps.

Chronic proton pump inhibitor therapy and the risk of colorectal cancer

BACKGROUND & AIMS

Chronic acid suppression by proton pump inhibitor therapy can lead to hypergastrinemia. Because existing evidence suggested an association between hypergastrinemia and colorectal cancer, we examined whether long-term proton pump inhibitor use is associated with an increased risk of colorectal cancer in a population-representative cohort.

METHODS

We conducted a nested case-control study among patients 50 years of age and older and with > or =5 years of colorectal cancer-free initial follow-up in the General Practice Research Database (1987-2002) from the United Kingdom. Cases consisted of all patients with an incident diagnosis of colorectal cancer. Using incidence density sampling, up to 10 controls were matched with each case on practice site and both duration and calendar time of follow-up before the index date. The primary exposure of interest was > or =5 years of cumulative proton pump inhibitor therapy. We assessed the presence of duration-response and dose-response effects.

RESULTS

We identified 4432 incident colorectal cancer cases and 44,292 controls. The adjusted odds ratio for > or =5 years of proton pump inhibitor exposure was 1.1 (95% confidence interval, 0.7-1.9). Among high-dose proton pump inhibitor users (ie, > or =1.5 defined daily doses/day), there was a nonstatistically significant trend toward an increased risk with increasing duration of use (test for trend, P = .2). However, patients with pernicious anemia were not at increased risk for colorectal cancer (adjusted odds ratio, 0.9; 95% confidence interval, 0.6-1.3).

CONCLUSIONS

Long-term proton pump inhibitor therapy at a regular dose is not associated with a significantly increased risk of colorectal cancer.

Long-term effects of elevated gastrin levels on calcitonin secretion

Gastrin and pentagastrin stimulate thyroid C cells and elevate serum calcitonin levels. Gastrin levels may be elevated when histamine-2 receptor blockers (H2RB) and/or proton pump inhibitors (PPI) are used, or in patients with pernicious anemia (PA). This study was designed to investigate the long-term effects of elevated gastrin levels on serum calcitonin levels. We conducted a pentagastrin stimulation test to evaluate C cell reserves in patients who had been using PPI and/or H2RB for an extended period, as well as in patients with PA. We compared the results with a healthy control group of similar age and sex. A total of 40 controls (26 women, 24 men) and 25 patients (15 women, 10 men) using H2RB and/or PPI, and 37 patients (24 women, 13 men) with PA were enrolled. The groups were similar in terms of mean age and sex distribution. Mean fasting gastrin levels, and mean baseline and pentagastrin-stimulated calcitonin levels were significantly higher in the H2RB+PPI and PA groups than in controls. No significant differences were observed between the H2RB+PPI and PA groups. There was no correlation between gastrin and calcitonin levels. However, mean calcitonin levels were significantly higher in subjects with high baseline gastrin levels than in controls. The prevalence of autoimmune thyroid disease was 32% in the PA group. Patients with PA and thyroiditis had significantly higher baseline gastrin levels than patients with PA only (p<0.01). PA with autoimmune thyroid disease had also significantly higher baseline and pentagastrin-stimulated calcitonin levels than did PA patients without autoimmune thyroid disease. In conclusion, chronic elevated gastrin levels led to elevated calcitonin levels. Further histopathological studies showing C cell hyperplasia are needed to confirm the mechanism of this relationship.

Gene deregulation in gastric cancer

Despite its decreasing frequency in the Western world during recent decades, gastric cancer is still one of the leading causes of cancer-related deaths worldwide. Due to the oligosymptomatic course of early gastric cancer, most cases are diagnosed in the advanced stages of the disease. The curative potential of current standard treatment continues to be unsatisfactory, despite multimodal approaches involving surgery, chemotherapy and radiotherapy. Novel therapeutics including small molecules and monoclonal antibodies are being developed and have been partially introduced into clinical use in connection with neoplastic diseases such as chronic myeloid leukemia, non-Hodgkin's lymphoma and colorectal cancer. Thorough understanding of the changes in gene expression occurring during gastric carcinogenesis may help to develop targeted therapies and improve the treatment of this disease. Novel molecular biology techniques have generated a wealth of data on up- and down-regulation, activation and inhibition of specific pathways in gastric cancer. Here, we provide an overview of the different aspects of aberrant gene expression patterns in gastric cancer.

Comparison of Prilosec OTCTM (omeprazole magnesium 20.6 mg) to placebo for 14 days in the treatment of frequent heartburn

PURPOSE

Consumer surveys have identified an over-the-counter (OTC) medication that provides complete and long-lasting relief of frequent heartburn as an unmet consumer need. The purpose of the two identical studies reported in this paper was to evaluate the safety and effectiveness of 10.3 and 20.6 mg omeprazole magnesium, referred to as Ome-Mg 10 and Ome-Mg 20, respectively (equivalent to 10 and 20 mg omeprazole) for the treatment of frequent heartburn administered as a novel 14-day OTC regimen.

SUBJECTS AND METHODS

Subjects with frequent heartburn (heartburn two or more days per week) took Ome-Mg 10, Ome-Mg 20, or placebo for 14 consecutive mornings. Statistical analyses compared percentage of subjects with no heartburn 24 h after the first dose, after the last dose (day 14), and percentage of days that subjects were heartburn-free. Nocturnal heartburn and heartburn rated no more than mild were also assessed.

RESULTS

Twenty-four hours following the first dose, nearly 50% of subjects receiving Ome-Mg 20 reported no heartburn, and more than 80% receiving Ome-Mg 20 had no more than mild heartburn. Both doses were significantly more effective than placebo on days 1 and 14 for percentage of subjects heartburn-free for 24 h (P < or = 0.003), and across all 14 days for percentage of heartburn-free days (P < 0.001). Ome-Mg 20 was significantly more effective than placebo in preventing nocturnal heartburn across all 14 days (P < 0.001). Ome-Mg was well tolerated.

CONCLUSION

These trials demonstrated the safety and effectiveness of a novel 14-day regimen of Ome-Mg 20 in completely preventing heartburn for 24 h establishing it as an excellent self-care treatment for frequent heartburn and supporting the approval of Prilosec OTC.

Omeprazole treatment of Korean patients: effects on gastric pH and gastrin release in relation to CYP2C19 geno- and phenotypes

This study aimed to investigate the effect of omeprazole on intragastric pH and gastrin release as well as the plasma concentration of omeprazole in relation to CYP2C19 genotypes after repeated doses in Korean patients. Twenty-six Korean patients with acid related disease were genotyped for CYP2C19 by allele specific PCR (wt/wt, CYP2C19*1/*1; wt/mut, CYP2C19*1/*2 or *1/*3; mut/mut, CYP2C19*2/*2, *2/*3 or *3/*3). Intragastric pH was monitored during 24 hr, and the plasma concentrations of omeprazole, hydroxyomeprazole, omeprazole sulfone and meal-stimulated gastrin were measured during 4 hr before and after 8 consecutive daily doses of 20 mg omeprazole. Unexpectedly the AUCs of omeprazole in the three genotypes were similarly high on Day 8. The mean 24 hr pH increased significantly in all three genotypes (paired t-test; P<0.0001), and the AUCs (4 hr) of gastrin in all patients increased markedly from 129+/-73 to 298+/-142 pMhr (P<0.0001). However, there was no statistically significant difference between the three genotypes in the mean pH and gastrin AUCs on Day 8. After 8 consecutive doses of 20 mg omeprazole, the gastric pH and the plasma gastrin were increased significantly in all three CYP2C19 genotypes, which were confirmed by high plasma concentrations of omeprazole in all three genotype groups. We suggest that the reason why the wt/wt had high concentrations of omeprazole similar to those in the other two genotype groups is that some of them were old with low CYP2C19 activity. In these patients omeprazole accumulated from the first to the eighth dose similar to that in the heterozygotes.

Gastrin-mediated activation of cyclin D1 transcription involves beta-catenin and CREB pathways in gastric cancer cells

Gastrin and its precursors promote proliferation in different gastrointestinal cells. Since mature, amidated gastrin (G-17) can induce cyclin D1, we determined whether G-17-mediated induction of cyclin D1 transcription involved Wnt signaling and CRE-binding protein (CREB) pathways. Our studies indicate that G-17 induces protein, mRNA expression and transcription of the G(1)-specific marker cyclin D1, in the gastric adenocarcinoma cell line AGSE (expressing the gastrin/cholecystokinin B receptor). This was associated with an increase in steady-state levels of total and nonphospho beta-catenin and its nuclear translocation, indicating the activation of the Wnt-signaling pathway. In addition, G-17-mediated increase in cyclin D1 transcription was significantly attenuated by axin or dominant-negative (dn) T-cell factor 4(TCF4), suggesting crosstalk of G-17 with the Wnt-signaling pathway. Mutational analysis indicated that this effect was mediated through the cyclic AMP response element (CRE) (predominantly) and the TCF sites in the cyclin D1 promoter, which was also inhibited by dnCREB. Furthermore, G-17 stimulation resulted in increased CRE-responsive reporter activity and CREB phosphorylation, indicating an activation of CREB. Chromatin immunoprecipitation studies revealed a G-17-mediated increase in the interaction of beta-catenin with cyclin D1 CRE, which was attenuated by dnTCF4 and dnCREB. These results indicate that G-17 induces cyclin D1 transcription, via the activation of beta-catenin and CREB pathways.

Pharmacokinetics of omeprazole in healthy adults and in children with gastroesophageal reflux disease

Studies of the pharmacokinetics of omeprazole in children with gastroesophageal reflux disease (GERD) remain scarce despite the vast number of reports on its efficacy. The objectives of this study were to assess the pharmacokinetics of omeprazole in healthy adults and in children with GERD. Omeprazole (Losec, delayed-release capsules) was administered orally to 18 healthy adults (mean age 36.8 years) and 12 children with GERD (mean age 6.1 years). Blood samples were collected over 5 hours, and plasma concentrations were assessed using liquid chromatography. Population pharmacokinetic parameters were calculated using NONMEM. A 1-compartment model with zero-order absorption and a lag time was used. The population approach was well suited to the limited number of samples available, and residual variability was low. Oral clearance (CL/F) and apparent volume of distribution (V(ss)/F) in healthy adults (Mean +/- SD: 0.62 +/- 0.27 L/h/kg and 0.76 +/- 0.26 L/kg, respectively) were not significantly different than those in children with GERD (0.51 +/- 0.34 L/h/kg and 0.66 +/- 0.25 L/kg, respectively). Healthy adults displayed a statistically significantly longer delay in drug absorption (Lag time: 0.62 +/- 0.15 hours) as compared with that observed in children with GERD (0.12 +/- 0.03 hours, P < 0.05). On the basis of these findings, omeprazole dosings on a milligram-per-kilogram basis are recommended with no further adjustments for the treatment of GERD in children.

Comparison of Two Provocative Tests for Calcitonin in Medullary Thyroid Carcinoma: Omeprazole vs Pentagastrin

Background: Provocative tests for calcitonin (CT) are fundamental in the diagnosis and follow-up of C-cell disease and in the detection of hereditary medullary thyroid carcinoma (MTC) carriers with unknown RET mutations. A recent report has proposed omeprazole, which can increase endogenous gastrin (GT), as a new provocative test for MTC.

Methods: We compared the omeprazole test (20 mg twice a day for 4 days) to the pentagastrin test (0.5 μg/kg of body weight) for the diagnosis and management of MTC. Twenty healthy individuals and 20 MTC patients with mildly or moderately increased basal CT serum concentrations underwent the pentagastrin and omeprazole tests.

Results: In MTC patients, the pentagastrin test produced a significantly higher increase in serum CT than did omeprazole. After the pentagastrin injection, several patients reported unpleasant side effects, including substantial tightness in 38 of 40 participants. No adverse effects were observed during the omeprazole test. A significant direct correlation was recorded between CT% (ratio of CT peak to basal value × 100) and GT% (ratio of GT peak to basal value × 100) during the omeprazole test in MTC patients (r = 0.73; P &lt;0.001).

Conclusions: In spite of several adverse effects, pentagastrin remains the best provocative test for the diagnosis of MTC. Omeprazole may be useful when pentagastrin is contraindicated or refused because of the unpleasant side effects, but further validation is needed.

Potential role of endocrine gastrin in the colonic adenoma carcinoma sequence

The role of hyper-gastrinaemia in the incidence of colonic cancer remains to be clarified. The aim of this study was to determine whether cholecystokinin-2 (CCK-2) receptor expression predicts the sensitivity of human colonic adenomas to the proliferative effects of serum hyper-gastrinaemia. Gene expression of the classical (74 kDa) CCK-2 receptor in human colonic adenoma specimens and cell lines, was quantified by real-time PCR. Western blotting, using a CCK-2 receptor antiserum, confirmed protein expression. A transformed human colonic adenoma was grown in SCID mice, with hyper-gastrinaemia induced by proton pump inhibitors. CCK-2 receptor blockade was achieved by using neutralising antiserum. Both human colonic adenoma cell lines and biopsies expressed CCK-2 receptor mRNA at levels comparable with CCK-2 receptor transfected fibroblasts and oxyntic mucosa. Western blotting confirmed immunoreactive CCK-2 receptor bands localised to 45, 74 and 82.5 kDa. Omeprazole and lansoprazole-induced hyper-gastrinaemia (resulting in serum gastrin levels of 34.0 and 153.0 pM, respectively) significantly increased the weight of the human adenoma grafts (43% (P=0.016) and 70% (P=0.014), respectively). The effect of hypergastrinaemia on tumour growth was reversed by use of antiserum directed against the CCK-2 receptor. Hyper-gastrinaemia may promote proliferation of human colonic adenomas that express CCK-2 receptor isoforms.

Adenocarcinoma of the rat esophagus in the presence of a proton pump inhibitor: a pilot study

This study examines the effects of a proton pump inhibitor on a rat model of duodenogastric reflux. Duodenoesophageal reflux was induced in 60 rats by performing a duodenesophagostomy. The study group received daily intraperitoneal injections of a proton pump inhibitor for 6 months and the control group received an equivalent injection of saline. Rats were examined at death for macroscopic tumor, dysplasia, adenocystic changes, papillomatosis, and adenocarcinoma. Five out of 19 rats in the study group and three out of 20 rats in the control group developed dysplastic/adenocarcinomatous changes. Ten of the rats in the study group died before the end of the study, as opposed to one in the control group (this is not statistically significant). There was no difference in the number of cancers that developed in the two groups. However, there was an insignificant trend to earlier appearance of detectable disease in the study group.

Pharmacological and pharmacodynamic essentials of H(2)-receptor antagonists and proton pump inhibitors for the practising physician

The suppression of gastric acid secretion with anti-secretory agents has been the mainstay of medical treatment for patients with acid-related disorders. Although the majority of Helicobacter pylori -related peptic ulcers can be healed with antibiotics, ulcer healing and symptom control can be significantly improved when antibiotics are given with anti-secretory agents, especially with a proton pump inhibitor. There is a dynamic relationship between the suppression of intragastric acidity and the healing of peptic ulcer and erosive oesophagitis and control of acid-related symptoms. The suppression of gastric acid secretion achieved with H(2)-receptor antagonists has, however, proved to be suboptimal for effectively controlling acid-related disorders, especially for healing erosive oesophagitis and for the relief of reflux symptoms. H(2)-receptor antagonists are also not effective in inhibiting meal-stimulated acid secretion, which is required for managing patients with erosive oesophagitis. Furthermore, the rapid development of tolerance to H(2)-receptor antagonists and the rebound acid hypersecretion after the withdrawal of an H(2)-receptor antagonist further limit their clinical use. Although low-dose H(2)-receptor antagonists are currently available as over-the-counter medications for self-controlling acid-related symptoms, their pharmacology and pharmacodynamics have not been well studied, especially in the self-medicating population. Proton pump inhibitors have been proved to be very effective for suppressing intragastric acidity to all known stimuli, although variations exist in the rapidity of onset of action and the potency of acid inhibition after oral administration at the approved therapeutic doses, which may have important clinical implications for the treatment of gastro-oesophageal reflux disease and perhaps for eradicating H. pylori infection when a proton pump inhibitor is given with antibiotics. Once-daily dosing in the morning is more effective than dosing in the evening for all proton pump inhibitors with respect to the suppression of intragastric acidity and daytime gastric acid secretion in particular, which may result from a better bio-availability being achieved with the morning dose. When higher doses are needed, these drugs must be given twice daily to achieve the optimal suppression of 24 hour intragastric acidity. Preliminary results have shown that esomeprazole, the optical isomer of omeprazole, given at 40 mg, is significantly more effective than omeprazole 40 mg, lansoprazole 30 mg or pantoprazole 40 mg for suppressing gastric acid secretion. However, more studies in different patient populations are needed to compare esomeprazole with the existing proton pump inhibitors with regard to their efficacy, cost-effectiveness and long-term safety for the management of acid-related disorders.

The role of gastrin in ulcer pathogenesis

Duodenal ulcer patients are characterized by an antrum-predominant, body-sparing, nonatrophic Helicobacter pylori (H. pylori) gastritis, which results in increased gastrin release and increased acid secretion. The increased gastrin release is caused by the infection impairing the acid-mediated inhibitory control of gastrin release. The elevated levels of the gastrin stimulate the healthy uninflamed, non-atrophic acid-secreting region of the stomach to secrete excess amounts of acid. The increased gastrin also exerts trophic effects on the oxyntic mucosa, causing hyperplasia of both the enterochromaffin-like cells and the parietal cells. These trophic changes in the mucosa further enhance its ability to secrete acid. The increased acid secretion results in an increased duodenal acid load, causing gastric metaplasia of the duodenal bulb and eventually the development of ulceration. In H. pylori-infected subjects without duodenal ulceration, a different pattern of gastritis is seen. This includes atrophy of the antrum, which reduces the number of G-cells and thus the degree of hypergastrinaemia induced by the antral infection. There are usually also varying degrees of inflammation and atrophy of the acid-secreting mucosa, which impair its ability to secrete acid in response to gastrin stimulation. The combined effects of the atrophy of the antrum and the inflammation of the antrum of the body mucosa therefore prevent H. pylori-induced acid hypersecretion and may result in varying degrees of hypochlorhydria. The particular pattern of gastritis that a subject develops in response to H. pylori infection and their likelihood of developing a duodenal ulcer is likely to be determinded by host genetic factors plus dietary factors.

Review article: rabeprazole's tolerability profile in clinical trials

Rabeprazole is a new member of a class of substituted benzimidazole drugs known as proton pump inhibitors. Comparative trials have demonstrated that it is at least as effective as omeprazole for the treatment of gastrooesophageal reflux disease (GERD), duodenal ulcers, or gastric ulcers. It is significantly more effective than histamine2-receptor antagonists for acid suppression, GERD healing and pain relief, and duodenal ulcer healing and pain relief. Adverse events reported during clinical trials provide an important indication of a medication's tolerability. We demonstrate that rabeprazole has a favourable adverse events profile. It is well tolerated in placebo-controlled studies and comparative trials with omeprazole and H2-receptor antagonists. Moreover, no dose adjustments are required for special populations, such as the elderly or patients with renal or mild-to-moderate hepatic disease. Adverse events data from clinical trials support the use of rabeprazole as a treatment for acid-related diseases.

Serum gastrin and chromogranin A during medium- and long-term acid suppressive therapy: a case-control study

BACKGROUND

Serum chromogranin A (CgA) is regarded as a reliable marker of neuroendocrine proliferation. We previously described increased serum CgA levels during short-term profound gastric acid inhibition.

AIM

To investigate serum gastrin and CgA levels in dyspeptic patients during continuous medium- (6 weeks to 1 year), or long-term (1-8 years) gastric acid suppressive therapy.

PATIENTS AND METHODS

114 consecutive dyspeptic patients referred for upper gastrointestinal endoscopy were enrolled in a cross-sectional, case-control study [62 patients on continuous antisecretory therapy, either with proton pump inhibitors (n = 47) or H2-receptor antagonists (H2RA) (n = 15) for gastro-oesophageal reflux disease with or without Barrett's oesophagus or functional dyspepsia, and 52 age- and sex-matched patients without medical acid inhibition and with normal endoscopic findings (control group)]. Omeprazole doses ranged from 20 mg to 80 mg daily and ranitidine from 150 mg to 450 mg daily. Fasting serum CgA and serum gastrin levels were measured by radioimmunoassay (reference values: serum CgA < 4.0 nmol/L; serum gastrin < 85 ng/L).

RESULTS

Fasting serum CgA levels positively correlated with serum gastrin in the entire study population (r = 0. 55, P = 0.0001). Median serum CgA values were higher in patients treated with a proton pump inhibitor than H2RA [2.8 (2.0-5.9) nmol/L vs. 2 (1.9-2.3) nmol/L, P < 0.002] and controls [2.8 (2.0-5.9) nmol/L vs. 1.8 (1.5-2.2) nmol/L, P < 0.0001) and did not differ between patients treated with H2RA or controls. Serum gastrin and CgA levels in patients on proton pump inhibitor therapy positively correlated with the degree and duration of acid inhibition. Patients on long-term proton pump inhibitor therapy had significantly higher fasting serum gastrin and CgA than those on medium-term proton pump inhibitor therapy [127 (73-217) ng/L vs. 49 (29-78) ng/L, P < 0.0001 and 4.8 (2.8-8) ng/L vs. 2.1 (1.9-2.6) ng/L, P < 0.001]. No such relation was found in patients on medium- vs. long-term H2RA. Overall, patients with positive Helicobacter pylori serology had higher serum gastrin and CgA levels than those with negative H. pylori serology [51 (27-119) ng/L vs. 27 (14-79) ng/L, P = 0.01, 2.4 (1.9-3.4) nmol/L vs. 2.0 (1.7-2.5) nmol/L, P = 0.05].

CONCLUSIONS

During long-term continuous proton pump inhibitor treatment, serum gastrin and CgA levels are significantly elevated compared to H2RA treatment and nontreated dyspeptic controls. H. pylori infection seems to affect gastric ECL cell secretory function. Increased serum CgA values during long-term profound gastric acid inhibition could reflect either gastric enterochromaffin-like cell hyperfunction or proliferative changes.

Omeprazole: calcitonin stimulation test for the diagnosis follow-up and family screening in medullary thyroid carcinoma

Medullary thyroid carcinoma (MTC) occurs sporadically but may also be inherited as part of the multiple endocrine neoplasia (MEN) type 2 syndrome. Screening of the patients and first degree relatives annually with basal and provocative tests for serum immunoreactive calcitonin (CT) levels is essential and enables potentially curative disease. Pentagastrin and calcium are the usual provocative agents used worldwide. We used endogenous gastrin (GT) release achieved by omeprazole, 20 mg b.i.d., to stimulate CT in 9 MTC, in 3 MEN 2A family members, and in 50 healthy control subjects. A steady and significant increase both in GT and CT levels was achieved in 9 MTC patients and 3 of the 14 family members tested, whereas in healthy controls the CT increase stimulated by GT was insignificant. Preliminary results showed that this new, safe, cheap, and outpatient-basis test can be used in MTC diagnosis, follow-up, and screening.

Ethnic and genetic determinants of omeprazole disposition and effect

OBJECTIVES

To compare the pharmacokinetics and dynamics of omeprazole in white and Chinese subjects.

METHODS

This double-blind two-stage study, performed in the clinical research center of a university hospital, evaluated 15 healthy nonsmoking men (eight white subjects and seven Chinese extensive metabolizers of mephenytoin). Blood samples were obtained over 24 hours after the eighth omeprazole dose (40 mg/day). Omeprazole, omeprazole sulfone, and hydroxyomeprazole pharmacokinetics were calculated from the respective plasma concentration-time curves. Twelve- and 24-hour integrated plasma gastriun (AUCgas12 and AUCgas24) were calculated from the respective plasma gastrin concentrations. A week before the initiation of omeprazole the activities of CYP2D6, CYP2C19, and CYP3A4 were determined by previously established methods.

RESULTS

Omeprazole concentrations were significantly lower (mean area under the plasma concentration time curve extrapolated to infinity [AUCO-infinity] +/- SEM; 7.53 +/- 1.21 versus 12.80 +/- 2.13 mumol.hr.L-1, respectively; p < 0.05) and its oral clearance greater (319 +/- 60 versus 183 +/- 35 ml/min, respectively; p < 0.05) in the white subjects than in the Chinese subjects. Omeprazole and omeprazole sulfone AUCO-infinity values were well correlated with the S/R mephenytoin ratio (r = 0.82 and r = 0.84, respectively; p < 0.001) and with urinary 4'-hydroxymephenytoin (r = -0.58 [p < 0.03] and r = -0.52 [p < 0.02], respectively). Fasting gastrin, AUCgas12, and AUCgas24 were significantly greater in the Chinese subjects than in the white subjects (30.0 +/- 6.4 versus 14.4 +/- 1.2 pmol, respectively [p < 0.02]; 661 +/- 114 versus 334 +/- 38 pmol.hr.L-1, respectively [p < 0.002]; and 1414 +/- 228 versus 747 +/- 99 pmol.hr.L-1, respectively [p < 0.004]). In addition, the S/R mephenytoin ratio and omeprazole AUCO-infinity correlated with the extent of omeprazole induced hypergastrinemia.

CONCLUSION

The metabolism of omeprazole and the rise in gastrin concentration after its administration is genetically determined and ethnically dependent.

Effects of pirenzepine on omeprazole-induced hypergastrinemia and acid suppression in peptic ulcer patients

Omeprazole effectively suppresses acid secretion, resulting in the long-term elevation of intragastric pH and serum gastrin level. Pirenzepine has been reported to inhibit gastrin secretion. This study was carried out to examine the effects of additional pirenzepine treatment on the hypergastrinemia and gastric acid suppression induced by omeprazole. Concentrations of serum gastrin and plasma somatostatin were measured in 28 peptic ulcer patients before treatment, after omeprazole treatment (20 mg/day) for 2 weeks, and after omeprazole and pirenzepine (100 mg/day) treatment for 2 weeks. The acid inhibitory effect of pirenzepine treatment in addition to omeprazole was evaluated by 24-h intragastric pH measurement in six healthy volunteers. Serum gastrin level was increased significantly, to 2.4-fold the pretreatment level, by omeprazole treatment. Additional treatment with pirenzepine suppressed serum gastrin level to 0.6-fold the omeprazole-treatment level. The serum somatostatin level was not altered significantly either by omeprazole treatment or by omeprazole and pirenzepine treatment. In healthy volunteers whose pH 3 holding time on 24-h intragastric pH monitoring was 70% by omeprazole treatment, omeprazole and pirenzepine treatment markedly increased the pH 3 holding time, to 89%. These findings suggest that pirenzepine is useful in reducing the undesirable effects of omeprazole-induced hypergastrinemia, i.e., the excessive trophic effect of omeprazole on the acid-secreting part of the stomach and the overstimulation of acid secretion. The additional pirenzepine treatment is also effective in suppressing acid secretion.

Pathophysiological effects of long-term acid suppression in man

A critical evaluation has been made of the available evidence in man of the effects of prolonged low acid states on the structure and function of the stomach. Various human models have been examined. 1. Ageing does not affect acid output from the normal male stomach, and there may be an increase in women. With progressive atrophy of the corpus mucosa, which is more frequent and rapid in patients with gastric ulcer, there is an associated loss of secretory function. Chronic gastritis and atrophy are the most important age-related changes, which in many cultures are hypothesized to develop via a prior Helicobacter pylori-related gastritis. However, H. pylori colonization of the mucosa decreases with increasing grades of gastric atrophy probably because intestinal metaplasia provides a hostile environment. Atrophy and intestinal metaplasia are associated with precancerous lesions and gastric cancer. Apparent hyperplasia of the gastric argyrophil endocrine cells is a common and spontaneous phenomenon in patients with atrophic gastritis, which in part may be related to the preferential loss of nonendocrine cells. 2. Pernicious anemia is associated with a complete lack of acid production, marked hypergastrinemia, and endocrine cell hyperplasia in the majority of patients. ECL-cell carcinoids and gastric cancer occur with a prevalence of 3-7%, and endoscopic surveillance in routine clinical practice is not warranted. 3. Gastric ECL-cell carcinoids are rare events that have been described in association with two diseases in man, pernicious anemia and Zollinger-Ellison syndrome as part of multiple endocrine neoplasia syndrome type I, and usually relate to marked hypergastrinemia and the presence of chronic atrophic gastritis with gastric antibodies or a genetic defect rather than the presence or absence of acid. Regression or disappearance of ECL-cell carcinoids, either spontaneously or after removal of the gastrin drive, has been recorded. Lymph node, and rarely hepatic, metastases are documented but death in these cases has been anecdotal. 4. Therapy with H2 antagonists may result in up to a twofold rise in serum gastrin levels but in man no endocrine cell hyperplasia has been recorded. However, the data for H2 antagonists on these aspects are very limited. There is no drug-related risk of gastric or esophageal cancer, although the incidence of the latter may be raised. Long-term treatment with omeprazole is associated with a two- to fourfold increase in gastrin levels over baseline values in one third of patients and apparent endocrine cell hyperplasia in 7% of cases overall.(ABSTRACT TRUNCATED AT 400 WORDS)

Omeprazole or ranitidine in long-term treatment of reflux esophagitis. The Scandinavian Clinics for United Research Group

BACKGROUND/AIMS

Patients with reflux esophagitis have rapid relapses after treatment withdrawal. This study was designed to investigate the relapse rate of symptomatic esophagitis during maintenance treatment with omeprazole or ranitidine.

METHODS

Patients with endoscopically verified acute erosive or ulcerative esophagitis were initially treated with 20-40 mg omeprazole daily for 8-12 weeks. After healing, the patients were randomized to maintenance treatment with omeprazole (20 or 10 mg each morning) or ranitidine (150 mg twice daily). Control endoscopy was performed at the end of the healing phase and after 12 months of maintenance treatment or symptomatic relapse.

RESULTS

Of 426 initially treated patients, 392 were healed and entered the maintenance study. The months of maintenance treatment with 20 mg omeprazole once daily (n = 131), 10 mg omeprazole once daily (n = 133), and 150 mg ranitidine twice daily (n = 128) were 72%, 62%, and 45%, respectively. Both the 10- and 20-mg doses of omeprazole were significantly better than the dose of ranitidine (P < 0.001 and P < 0.005, respectively). There was no significant difference between the 10- and 20-mg doses of omeprazole (P = 0.06).

CONCLUSIONS

Maintenance treatment with omeprazole (20 or 10 mg once daily) is superior to ranitidine (150 mg twice daily) in keeping patients with erosive reflux esophagitis in remission over a 12-month period.

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.

Inhibition of omeprazole induced hypergastrinaemia by SMS 201-995, a long acting somatostatin analogue in man

Whether the long acting somatostatin analogue SMS 201-995 (octreotide, Sandostatin) could inhibit the basal and meal stimulated hypergastrinaemia and hyperpepsinogenaemia induced by omeprazole was investigated. Eight healthy subjects were randomised to receive five day courses of SMS 201-995 (25 micrograms subcutaneously three times daily), omeprazole (40 mg once a day), a combination of both drugs, or placebo. Basal and meal stimulated serum gastrin and basal serum pepsinogen A and C values were measured the day before treatment, on day five of treatment, and the day after each course of treatment. Omeprazole caused significant increases in basal and meal stimulated peak and integrated serum gastrin values and pepsinogen A and C levels, which were still significantly raised the day after stopping omeprazole treatment. Giving SMS 201-995 with omeprazole significantly reduced any omeprazole induced increases in basal and meal stimulated peak and integrated serum gastrin levels; serum pepsinogen A and C values were significantly inhibited too. Serum gastrin values during combined therapy were not significantly different from those during placebo treatment, whereas pepsinogen A and C levels were still significantly raised. On the day after stopping combined therapy, basal and meal stimulated peak and integrated serum gastrin and serum pepsinogen C (but not pepsinogen A) levels were not significantly different from values obtained on the day after stopping omeprazole alone. SMS 201-995 without omeprazole significantly inhibited basal and meal stimulated peak and integrated serum gastrin levels. Pepsinogen A was also significantly inhibited by SMS 210-995, but the reduction in pepsinogen C failed to reach statistical significance. In conclusion, SMS 201-995 prevents basal and meal stimulated increases in serum gastrin during omeprazole therapy. This finding may have clinical importance in the few patients who have pronounced hypergastrinaemia because of profound long acting acid inhibition.

Effect of short- and long-term treatment with omeprazole on cell cycle distribution in the gastric mucosa. Results of a flow cytometric study

Omeprazole may exert an effect on gastric mucosal proliferation by inhibiting gastric acid secretion and increasing serum gastrin levels. It may also influence the kinetics of endocrine cells and the oxyntic mucosa. The aim of the present study was to evaluate the cell cycle in different gastric compartments following short- (1 month) and long-term (6 months) administration of two different dosages of omeprazole by means of a flow cytometric method. We also determined serum gastrin levels at the same time. No differences in cell cycle distribution of the antrum, body, and fundus were found in the two different dosage groups after 1 month of therapy, considering the synthetic phase (S-phase) of the cell cycle. A statistically significant increase in S-phase was reported after long-term therapy in the mucosa of the fundus and body of the stomach in both groups. Gastrin levels showed no clear correlation with cell cycle distribution variables. We postulate a proliferative adaptation of the oxyntic mucosa to long-term drug administration not mediated by gastrin influence.

Short report: high-dose omeprazole and amoxycillin in the treatment of Helicobacter pylori-associated duodenal ulcer

Thirteen consecutive patients with active duodenal ulcer disease were assigned to a treatment schedule with high-dose omeprazole and amoxycillin. Duodenal ulcer was diagnosed endoscopically in all patients, at which time antral biopsies were taken for culture and histology. All were positive for Helicobacter pylori and histological gastritis. Treatment was for 2 weeks: 80 mg omeprazole daily plus 500 mg amoxycillin syrup t.d.s. in the first week, followed by 40 mg omeprazole daily in the second week. Repeat gastroscopy was performed 4 weeks after completion of treatment in all patients. Duodenal ulcer healing occurred in 4/13 patients. H. pylori eradication was achieved in 2/4 patients with healed ulcers and in 3/9 patients with persistent ulceration. This study suggests that a short period of treatment with high-dose omeprazole and amoxycillin achieves low rates of ulcer healing and H. pylori eradication.

Pharmacology of gastric acid inhibition

Gastric acid secretion is precisely regulated by neural (acetylcholine), hormonal (gastrin), and paracrine (histamine; somatostatin) mechanisms. The stimulatory effect of acetylcholine and gastrin is mediated via increase in cytosolic calcium, whereas that of histamine is mediated via activation of adenylate cyclase and generation of cAMP. Potentiation between histamine and either gastrin or acetylcholine may reflect postreceptor interaction between the distinct pathways and/or the ability of gastrin and acetylcholine to release histamine from mucosal ECL cells. The prime inhibitor of acid secretion is somatostatin. Its inhibitory paracrine effect is mediated predominantly by receptors coupled via guanine nucleotide binding proteins to inhibition of adenylate cyclase activity. All the pathways converge on and modulate the activity of the luminal enzyme, H+,K(+)-ATPase, the proton pump of the parietal cell. Precise information on the mechanisms involved in gastric acid secretion and the identification of specific receptor subtypes has led to the development of potent drugs capable of inhibiting acid secretion. These include competitive antagonists that interact with stimulatory receptors (e.g. muscarinic M1-receptor antagonists and histamine H2-receptor antagonists) as well as non-competitive inhibitors of H+,K(+)-ATPase (e.g. omeprazole). The histamine H2-receptor antagonists (cimetidine, ranitidine, famotidine, nizatidine and roxatidine acetate) continue as first-line therapy for peptic ulcer disease and are effective in preventing relapse. Although they are generally well tolerated, histamine H2-receptor antagonists may cause untoward CNS, cardiac and endocrine effects, as well as interfering with the absorption, metabolism and elimination of various drugs. The dominance of the histamine H2-receptor antagonists is now being challenged by omeprazole. Omeprazole reaches the parietal cell via the bloodstream, diffuses through the cytoplasm and becomes activated and trapped as a sulfenamide in the acidic canaliculus of the parietal cell. Here, it covalently binds to H+,K(+)-ATPase, the hydrogen pump of the parietal cell, thereby irreversibly blocking acid secretion in response to all modes of stimulation. The main potential drawback to its use is its extreme potency which sometimes leads to virtual anacidity, gastrin cell hyperplasia, hypergastrinaemia and, in rats, to the development of carcinoid tumours. The cholinergic receptor on the parietal cell has recently been identified as an M3 subtype and that on postganglionic intramural neurones of the submucosal plexus as an M1 subtype.(ABSTRACT TRUNCATED AT 400 WORDS)

Helicobacter pylori and hypergastrinaemia during proton pump inhibitor therapy

The rise in serum gastrin and pepsinogen I after 5 days' treatment with the proton pump inhibitor pantoprazole (40 mg/day) was examined in eight duodenal ulcer patients with Helicobacter pylori infection and compared with eight in whom it had been eradicated. Before treatment, the post-prandial serum gastrin concentrations were higher in the H. pylori-positive than -eradicated patients (p less than 0.05). The median rise in pre-prandial serum gastrin concentrations on treatment was similar in the H. pylori-positive (41%) and -eradicated patients (45%). The rise in post-prandial serum gastrin was also similar in the H. pylori-positive (81%) and -eradicated patients (69%), resulting in significantly higher gastrin concentrations during treatment in the former. The median rise in serum pepsinogen I on treatment was greater in the H. pylori-positive (114%) than in the -eradicated patients (8%), resulting in significantly higher concentrations during treatment in the former. These observations indicate that eradication of H. pylori may be a means of moderating the hypergastrinaemia caused by acid-inhibitory therapy. They also indicate that H. pylori-related hypergastrinaemia is not due to an increase of the antral surface pH by the bacterium's urease activity.

Weekend treatment with 20 and 40 mg omeprazole: effect on intragastric pH, fasting and postprandial serum gastrin, and serum pepsinogens

Weekend treatment with 20 mg omeprazole reduces ulcer relapse rates but the results may improve with a higher dose regimen. We have evaluated three day weekend treatment with 20 and 40 mg doses of omeprazole in eight healthy subjects in a double blind crossover study. Twenty four hour ambulatory intragastric pH and basal and meal stimulated serum gastrin and serum pepsinogens A and C values were studied. The investigations began on the Friday before the third weekend course of omeprazole and were repeated on alternate days, except Sundays, for two weeks. When compared with values before the study, median 24 hour intragastric pH and basal and meal stimulated gastrin concentrations were significantly (p less than 0.01-0.05), but transiently, raised with both doses of omeprazole. Basal pepsinogen A and C values were significantly (p less than 0.01) increased on all study days, but did not return to their pre-study values before the next weekend dose, except for pepsinogen C in subjects treated with 20 mg omeprazole. A dose dependent effect was found for all parameters studied (p less than 0.05). In conclusion, weekend treatment with 20 and 40 mg omeprazole produces pronounced and dose dependent increases in intragastric pH, basal and meal stimulated serum gastrin, and basal serum pepsinogen A and C without inducing prolonged hypoacidity or hypergastrinaemia. Weekend treatment with 40 mg omeprazole merits further study in the prevention of peptic ulcer relapse.

The cephalic and gastric phases of gastric secretion during H2-antagonist treatment

The antisecretory effects of H2-receptor antagonists are limited by food ingestion. The contributions of the cephalic-vagal and gastrinergic mechanisms to this interaction were examined in two 14-hour randomized, cross-over studies in 24 healthy volunteers. In the first study, either ranitidine or placebo was administered IV by a pH-feedback-controlled infusion pump during fasting, modified sham feeding, or food ingestion. Sham feeding resulted in a well-defined and abrupt interaction with the antisecretory effect of ranitidine (lasting 2-3 hours), after which fasting pH levels were regained. The second study, with the same design, showed that gastrin release occurred during this cephalic-vagal phase but was not attenuated by the additional infusion of the anticholinergic pirenzepine. Following eating, intragastric acidity increased and remained elevated for more than 6 hours. This increase was accompanied by prolonged hypergastrinemia, which was not diminished by pirenzepine. Pirenzepine did, however, enhance the antisecretory effect of ranitidine after both sham feeding and food ingestion. The interaction of food or sham feeding with the antisecretory effect of H2 antagonists is a consistent phenomenon. In both the cephalic-vagal and the gastric phases of secretion, this interaction appears to be partially mediated by a noncholinergic release of gastrin.

Omeprazole. An updated review of its pharmacology and therapeutic use in acid-related disorders

Omeprazole is the first of a new class of drugs, the acid pump inhibitors, which control gastric acid secretion at the final stage of the acid secretory pathway and thus reduce basal and stimulated acid secretion irrespective of the stimulus. In patients with duodenal or gastric ulcers, omeprazole as a single 20 mg daily dose provides more rapid and complete healing compared with ranitidine 150 mg twice daily or 300 mg at nighttime, or cimetidine 800 or 1000 mg/day. Patients poorly responsive to treatment with histamine H2-receptor antagonists respond well to omeprazole--most ulcers healed within 4 to 8 weeks of omeprazole 40 mg/day therapy. Omeprazole 20 or 40 mg/day has been administered as maintenance therapy for peptic ulcer disease for up to 5.5 years with very few ulcer recurrences. In patients with erosive or ulcerative oesophagitis, omeprazole 20 or 40 mg/day produces healing in about 80% of patients after 4 weeks, and is superior to ranitidine with respect to both healing and symptom relief. Healing rates of greater than 80% are achieved after 8 weeks in patients with severe reflux oesophagitis unresponsive to H2-receptor antagonists. Maintenance therapy with a daily 20 mg dose prevents relapse in about 80% of patients over a 12-month period. Omeprazole is considered to be the best pharmacological option for controlling gastric acid secretion in patients with Zollinger-Ellison syndrome. Daily dosages of 20 to 360 (median 60 to 70 mg successfully reduce basal acid output to target levels (less than 10 mmol/h or less than 5 mmol/h in patients with severe oesophagitis or partial gastrectomy) during treatment for up to 4 years. Omeprazole is well tolerated in short term studies (up to 12 weeks); the reported incidence of serious side effects (about 1%) being similar to that seen in patients treated with an histamine H2-receptor antagonist. The longer term tolerability of omeprazole has been investigated in patients treated for up to 5.5 years. Slight hyperplasia, but no evidence of enterochromaffin-like (ECL) cell dysplasia or neoplasia or ECL cell carcinoids has been reported. ECL cell carcinoids have been observed in rats after life-long treatment with high doses of omeprazole or ranitidine, or in rats with partial corpectomy; the weight of experimental evidence indicates that this is a result of prolonged hypergastrinaemia.(ABSTRACT TRUNCATED AT 400 WORDS)

Repeated intravenous bolus injections of omeprazole: effects on 24-hour intragastric pH, serum gastrin, and serum pepsinogen A and C

We determined the effect of four times daily dosing with intravenous omeprazole on 24-h intragastric acidity, serum gastrin, and serum pepsinogen A and C in 10 fasting subjects (median age, 23.5 years). Two dose regimens (80-20-20-20 mg and 80-40-40-40 mg) were compared in a randomized placebo-controlled crossover study. Intragastric pH was continuously monitored during 24 h, using combined glass electrodes, and blood samples were taken every 6 h. Repeated boluses of omeprazole every 6 h significantly increased (p less than 0.01) the median 24-h intragastric pH compared with placebo (median pH, 3.7 (140 mg/day), 4.3 (200 mg/day), and 1.4 (placebo)) but failed to continuously raise pH levels above 4.0 in 8 (140 mg/day) or 9 (200 mg/day) of 10 subjects. No advantage of the 200-mg dose over the 140-mg dose was demonstrated. A cumulative effect of intravenous omeprazole was shown after repeated boluses but also a marked interindividual variation in response, which was correlated with the omeprazole area under the plasma concentration time curve. A significant elevation of serum gastrin coincided with the increased pH levels, which was followed after 12-18 h by a significant increase of both serum pepsinogens.

Omeprazole in elderly duodenal ulcer patients: relationship between reduction in gastric acid secretion and fasting plasma gastrin

The effect of omeprazole on acid secretion and gastrin levels has been investigated in 10 elderly duodenal ulcer patients in remission. Doses of 5, 10, 20 and 40 mg omeprazole were given once daily for 7 consecutive days and the basal (BAO) and peak (PAO) acid output and fasting plasma gastrin concentration were measured 24 h after the seventh dose. Omeprazole suppressed PAO significantly and dose-dependently after doses of 10, 20 and 40 mg, the suppression being 42%, 75% and 85%, respectively. No patient showed complete inhibition of PAO and at least 20 mg had to be given to obtain a marked inhibitory effect in all patients. Increasing the dose to 40 mg had only a slight additional effect compared to 20 mg. There was a relationship between degree of acid inhibition and the increase in fasting plasma gastrin. PAO had to be suppressed by more than 80% before a moderate increase in fasting plasma gastrin was observed. The optimal once-daily oral dose of omeprazole for inhibition of acid secretion in elderly patients appears to be 20 mg. Omeprazole 20-40 mg may cause a moderate increase in fasting plasma gastrin.

Ultrastructural morphometry of gastric endocrine cells before and after omeprazole. A study in the oxyntic mucosa of duodenal ulcer patients

Long-term toxicological experiments with inhibitors of acid secretion were found to induce hyperplasia and eventually carcinoid tumors of the enterochromaffin-like cells of the oxyntic mucosa. To evaluate the effects of 6 months' treatment with omeprazole in humans, the oxyntic endocrine cells were morphometrically investigated at the ultrastructural level in five patients with active duodenal ulcer. No omeprazole-induced changes were found in the volume density of the total endocrine cell population and specific cell types (including the enterochromaffin-like cell) as well as in the other cytological parameters investigated (number of cell profiles per unit area, mean cross-sectional area of cell profiles, nuclear-cytoplasmic ratio, and density of cytoplasmic secretory granules). Both pretreatment and post-treatment values in our patients with duodenal ulcer significantly differed from those of a previous investigation of healthy volunteers with regard to the volume density of enterochromaffin-like cells and non-granulated cells, which increased, and of D cells, which markedly decreased. The latter result may provide a cellular basis for impairment in the paracrine release of fundic somatostatin in peptic ulcer disease. Finally, morphometric data on endocrine cell volume density provided by electron microscopy were found to correlate with those obtained in the same patients using light microscopy techniques (Grimelius silver impregnation and chromogranin A immunostaining). It is concluded that 6 months' treatment with pharmacological doses of omeprazole is devoid of appreciable trophic effect on endocrine cells of human oxyntic mucosa.

Prevention of relapse of reflux esophagitis after endoscopic healing: the efficacy and safety of omeprazole compared with ranitidine

Ninety-eight patients with erosive and/or ulcerative esophagitis unhealed after at least 3 months' treatment with standard doses of cimetidine (greater than or equal to 1200 mg daily) or ranitidine (greater than or equal to 300 mg daily) were primarily included in an acute healing phase study, and 51 were allocated to 40 mg omeprazole once daily and 47 to 300 mg ranitidine twice daily. After 12 weeks of treatment, 46 (90%) patients given omeprazole were healed, compared with 22 (47%) allocated to ranitidine. Healed patients were then given maintenance treatment with either 20 mg omeprazole once daily or 150 mg ranitidine twice daily for 12 months. Plasma gastrin was determined and gastric mucosal biopsy specimens were obtained during the entire study to assess the structure of the exocrine and endocrine cell populations of the oxyntic mucosa. Sixty-seven per cent of the total number of patients randomized to omeprazole were maintained in clinical and endoscopic remission throughout the 12-month study period as compared with only 10% among those given ranitidine (p less than 0.0001). After 4 weeks of omeprazole treatment basal gastrin levels were slightly increased, with a 95% confidence interval for the change of from 8.6 to 16.9 pmol/l. No further increase in basal gastrin levels was observed during the ensuing study months. No significant histopathologic lesion was found in the oxyntic gland mucosa. In conclusion, omeprazole was far superior to ranitidine in preventing recurrence, a goal achieved without adverse events and significant abnormalities in the oxyntic mucosal exocrine or endocrine cells but with a moderate increase in basal gastrin levels.

24-hour intragastric acidity and plasma gastrin after omeprazole treatment and after proximal gastric vagotomy in duodenal ulcer patients

The relationship between suppressed gastric acidity and the increase in plasma gastrin levels after pharmacological and surgical treatment of peptic ulcer disease were compared in this study. Eight patients with chronic duodenal ulcer and referred for proximal gastric vagotomy were studied. 24-hour intragastric acidity and plasma gastrin levels were investigated in the same patients on three consecutive occasions: preentry without any treatment; after 4 weeks of administration of 20 mg of omeprazole daily, and 4-6 months after proximal gastric vagotomy. Intragastric acidity was slightly more reduced by omeprazole (94%) than after proximal gastric vagotomy (78%), with no difference found during the day or night with either. Plasma gastrin levels increased slightly more after proximal gastric vagotomy [284% (median, 2120 pmol.h/L; range, 733-2831 pmol.h/L)] than after omeprazole administration [186% (median, 1586 pmol.h/L; range, 495-2573 pmol.h/L)]. There is strong evidence that the increased plasma gastrin concentration following omeprazole treatment is caused by the reduced intragastric acidity. The slight increase in plasma gastrin concentration following proximal gastric vagotomy despite a lesser reduction in intragastric acidity may be the result of additional effects on gastrin release by the vagotomy. Both treatments resulted in a modest increase in plasma levels of gastrin that were far below the gastrin levels observed in achlorhydric patients, e.g., patients with pernicious anemia.

Tolerance to oral H2-receptor antagonists

The acid-inhibitory action of H2-receptor antagonists was shown to decrease after one to two weeks of dosing in healthy volunteers. This tolerance was evaluated in three randomized, placebo-controlled trials with the H2-receptor antagonists famotidine, 40 mg given after the evening meal for 28 days; ranitidine, 300 mg four times a day for seven days followed by 300 mg at night until day 28; and ranitidine, 300 mg three times a day vs 300 mg at night for 14 days. Continuous 24-hr pH monitoring with glass electrodes was performed under fed conditions. The median 24-hr pH decreased from 3.2 on day 1 with famotidine 40 mg to 1.9 on day 28 (P less than 0.0012). After seven days of dosing with ranitidine 300 mg four times a day the median 24-hr pH dropped from 5.0 on day 1 to 3.0 on day 7 (P less than 0.001) and then to 2.2 with ranitidine 300 mg at night on day 28. With ranitidine 300 mg three times a day the median 24-hr pH fell from 4.3 on day 1 to 2.4 on day 14 (P less than 0.0005). With ranitidine 300 mg at night the respective pH values were 2.5 and 1.8 (P less than 0.003). Tolerance to H2-receptor antagonists given in a single evening dose was only evident during the night, whereas tolerance occurred throughout the day and night with the three- and four-times-a-day regimens. A large increase in the interindividual variability of pH response was seen during the nighttime.

Serum gastrin levels during long-term omeprazole treatment

Serum gastrin was determined in 33 patients during treatment with the proton pump inhibitor omeprazole. After 4 weeks of therapy, gastrin levels increased to a median of 55 pg/ml compared to 15 pg/ml prior to omeprazole (P less than 0.001). There was a close correlation (r = 0.939; P less than 0.001) between pre-treatment gastrin and levels at 4 weeks. Comparison of serum gastrin concentrations at 1 month of omeprazole with levels at 6 (n = 21) and 12 months (n = 12) continuous therapy revealed a close correlation (r = 0.961 and r = 0.882, respectively; P less than 0.001) despite dose adjustment. In marked hypochlorhydria documented by continuous pH monitoring, serum gastrin varied from normal up to profound hypergastrinaemia. These results demonstrate that the serum gastrin increase under powerful acid-inhibitory drug therapy depends upon a number of variables. (a) Only in patients with elevated gastrin levels, prior to omeprazole treatment, can moderate to marked hypergastrinaemia during omeprazole be expected. (b) Gastrin increases reached during the initial period of omeprazole treatment remain constant during long-term therapy. (c) Acid inhibition itself is not necessarily associated with an increase in serum gastrin in every patient, which suggests that the individual sensitivity of the gastrin cell to acid inhibition is more important for serum gastrin changes than the degree of acid inhibition itself.