Nocturnal intragastric acidity during and after a period of dosing with either ranitidine or omeprazole

Rebound Acid Hypersecretion after Withdrawal of Long-Term Proton Pump Inhibitor (PPI) Treatment-Are PPIs Addictive?

Proton pump inhibitors (PPIs) are widely used in the long-term treatment of gastroesophageal reflux disease (GERD) and other upper gastrointestinal disorders, such as the healing of peptic ulcers and/or prophylactic treatment of peptic ulcers. PPIs are also widely used as symptomatic treatment in patients with functional dyspepsia. One of the adverse effects of the long-term use of PPI is rebound acid hypersecretion (RAHS), which can occur after the withdrawal of PPI therapy due to a compensatory increase in gastric acid production. Mechanisms of the RAHS have been well established. Studies have shown that pentagastrin-stimulated acid secretion after the discontinuation of PPIs increased significantly compared to that before treatment. In healthy volunteers treated with PPIs, the latter induced gastrointestinal symptoms in 40-50% of subjects after the discontinuation of PPI therapy but after stopping the placebo. It is important for practicing physicians to be aware and understand the underlying mechanisms and inform patients about potential RAHS before discontinuing PPIs in order to avoid continuing unnecessary PPI therapy. This is important because RAHS may lead patients to reuptake PPIs as symptoms are incorrectly thought to originate from the recurrence of underlying conditions, such as GERD. Mechanisms of RAHS have been well established; however, clinical implications and the risk factors for RAHS are not fully understood. Further research is needed to facilitate appropriate management of RAHS in the future.

Clinical consequences of controversies in gastric physiology

Studies on the regulation of gastric acid secretion started more than 100 years ago at an early phase of experimental physiology. In nearly the whole last century there were disputes about the interpretation of the findings: the interaction between the three principle gastric acid secretagogues acetylcholine, gastrin and histamine, the cell producing the relevant histamine which turned out to be the ECL cell, the ability of the ECL cell to divide and thus develop into tumours, the classification of gastric carcinomas and the mechanism for Helicobacter pylori carcinogenesis. The elucidation of the central role of the ECL cell and thus its main regulator, gastrin, solve all these controversies, and gives a solid base for handling upper gastrointestinal diseases.

Risk Factors for Developing Peritonitis Caused by Micro-Organisms of Enteral Origin in Peritoneal Dialysis Patients

Objective

To investigate the risk factors associated with the development of peritonitis caused by enteral bacteria in peritoneal dialysis patients, including the prescription of gastric acid inhibitors as a potential risk factor.

Design

Retrospective single-center study.

Setting

Tertiary university hospital.

Patients an d Main Outcome Measures

Fifty-five patients who entered into our continuous ambulatory peritoneal dialysis (CAPD) program during the last 6 years were included. Multiple logistic regression analysis was used to establish the best determinants over the development of at least one episode of enteric peritonitis. The predictive variables included in the model were: age, gender, diabetic versus nondiabetic, polycystic versus nonpolycystic kidney diseases, history of constipation, presence or absence of moderate/severe malnutrition, peritoneal transport characteristics, peritoneal protein losses, rate of exit-site infections, rate of total peritonitis, intestinal abnormalities, and treatment with inhibitors of gastric acid secretion.

Results

The total number of peritonitis episodes during the studied period was 88, which clustered in 34 of 55 patients. Fourteen (16%) were caused by enteric microorganisms in 10 patients: Escherichia coli (6), Klebsiella sp (2), Enterobacter sp (1), and Enterococcus sp (5). Nine of 10 patients who developed enteric peritonitis were on gastric acid inhibitors (3 patients on omeprazole and 6 patients on H2-antagonists), while 15 of 45 patients who did not develop enteric peritonitis were on gastric acid inhibitors (all of them on H2-blockers). There were temporal relationships between the start of gastric acid inhibitors and the development of enteric peritonitis in 6 of 9 patients who were on this medication. Four of 10 patients who developed enteric peritonitis had diverticulosis. Ten of 45 patients who did not develop enteric peritonitis had been diagnosed with diverticulosis of the colon or sigmoid prior to entry to CAPD. The unique patient who was not on gastric acid inhibitors and developed enteric peritonitis, had been diagnosed with chronic atrophic gastritis with achlorhydria. By multiple logistic regression analysis, the treatment with gastric acid inhibitors was the only independent variable that entered into the best predictive equation over the development of enteric peritonitis (Iog likelihood ratio = -26.077, odds ratio = 18; 95% CI odds ratio: 2 - 155).

Conclusion

Gastric acid inhibitors may increase the risk for developing enteric peritonitis in peritoneal dialysis patients.

Gastric Acid Suppression and the Risk of Enteric Peritonitis in Peritoneal Dialysis Patients

Objective

Peritonitis caused by enteric organisms in peritoneal dialysis (PD) patients is associated with greater morbidity and mortality than peritonitis with non-enteric organisms. One reported risk factor for enteric peritonitis (EP) is gastric acid suppression, with two small studies providing conflicting results. The objective of this study was to determine, using a larger patient population, whether gastric acid suppressants are associated with an increased risk of EP.

Patients and Methods

Using a single-center case-control design, information on episodes of EP occurring between 2003 and 2006 was collected. Control episodes were all non-enteric episodes of peritonitis that occurred during the same time interval. Proton pump inhibitor (PPI) or H2-blocker (H2B) use prior to development of peritonitis was documented.

Results

A total of 228 peritonitis episodes among 137 patients met inclusion criteria. In 32% of episodes, the causative organism was enteric. Gastric acid suppressant use was documented in 46% of episodes, with the majority on PPIs. Overall, gastric acid suppression was not associated with a higher EP risk ( p = 0.17). In a post hoc analysis, PPIs were not associated with EP [odds ratio (OR) 1.3, 95% confidence interval (CI) 0.7 – 2.4; p = 0.42], whereas H2Bs were associated with a higher risk of EP (OR 2.9, 95% CI 1.1 – 7.7; p = 0.04), although the number of patients on H2Bs was small.

Conclusion

Overall, gastric acid suppression was not associated with an increased risk of peritonitis with enteric organisms. While PPI use appears to be safe for PD patients with appropriate indications, the potential risk of EP with H2Bs requires further investigation.

Adverse Effects of Proton Pump Inhibitors-Evidence and Plausibility

Proton pump inhibitors (PPIs) have been increasingly used over the last decades and there are concerns about overuse and the numerous reported side-effects. It is uncertain whether associations between PPI use and potential side effects are causal. However, important evidence from experimental and mechanistic studies that could support a causal relationship may have been underestimated by epidemiologists and meta-analysists. In the current manuscript we review the combined epidemiological and mechanistic evidence of the adverse effects of PPI use.

The regulation of gastric acid secretion - clinical perspectives

The purpose of this review, based upon 40 years of research, is to clear old controversies. The gastric juice is a strong acid with active enzymes (pepsin and lipase); ideal for killing swallowed microorganisms. Totally isolated rat stomach and histamine determination. Human gastric carcinomas were examined for ECL cell differentiation because tumours found in rodents after dosing with inhibitors of acid secretion were reclassified to be of ECL cell origin. The gastrin receptor is localized to the ECL cell only, where gastrin stimulates the function and growth. Drug-induced hypo-acidity induces hypergastrinaemia and ECL cell hyperplasia responsible for rebound acid hypersecretion. Every condition with long-term hypergastrinaemia disposes to ECL cell neoplasia. In man, both atrophic gastritis and gastrinoma lead to ECL cell carcinoids. Proton pump inhibitors induce hypergastrinaemia with ECL cell hyperplasia and ECL cell carcinoids that disappear when stopping treatment. The gastrin antagonist netazepide induces regression of ECL cell carcinoids due to atrophic gastritis. Human gastric carcinomas of diffuse type, particularly the signet-ring subtype, show ECL cell differentiation, suggesting involvement of gastrin in the carcinogenesis. Helicobacter pylori (Hp) causes gastritis and peptic ulcer, and when infecting the antrum only gives a slight hypergastrinaemia with acid hypersecretion predisposing to duodenal ulcer, but protecting from gastric cancer. When Hp infection spreads to oxyntic mucosa, it induces atrophy, reduced acid secretion and marked hypergastrinaemia and cancer.It is remarkable that the interaction between Hp and gastrin may explain the pathogenesis of most diseases in the upper gastrointestinal tract.

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.

Dyspeptic symptom development after discontinuation of a proton pump inhibitor: a double-blind placebo-controlled trial

OBJECTIVES

Conflicting data exist on whether discontinuation of proton pump inhibitors (PPIs) is associated with rebound secretion of gastric acid.

METHODS

A total of 48 healthy Helicobacter pylori-negative volunteers (24 females) were randomized in a double-blinded manner to treatment with either pantoprazole 40 mg or placebo once daily for 28 days. Dyspeptic symptoms were registered daily using the Glasgow dyspepsia score (GDS) 2 weeks before, during, and 6 weeks after treatment. Plasma levels of gastrin and serum levels of chromogranin-A levels were measured before, during, and after treatment.

RESULTS

During the 2 weeks before treatment, the placebo group had a mean GDS of 0.20 + or - 0.7 compared with the pantoprazole group score of 0.54 + or - 1.3 (NS). No significant differences between the symptom severity scores of the two groups were shown during the treatment period. During the first week after discontinuation of treatment, the pantoprazole group had a mean symptom score of 5.7 + or - 11.7 vs. 0.74 + or - 2.6 in the placebo group (P<0.01). A total of 11 out of 25 (44%) subjects in the pantoprazole group developed dyspepsia compared with 2 out of 23 (9%) in the placebo group (P<0.01). During the second week of follow-up, the pantoprazole group had a mean symptom score of 1.6 + or - 3.4 compared with 0 + or - 0 in the placebo group (P<0.05). There were no significant differences in the mean symptom score for the pantoprazole group (1.1 + or - 0.6) compared with the placebo group (0.4 + or - 0.3) during the third week of follow-up. Symptom scores during the first week after treatment correlated with basal (P<0.01) and meal-stimulated (P<0.01) gastrin levels at the end of treatment.

CONCLUSIONS

A 4-week course of pantoprazole seems to induce dyspeptic symptoms in previously asymptomatic healthy H. pylori-negative subjects. The correlation between symptom score and gastrin levels suggests that these symptoms are due to acid rebound hypersecretion and seem to be related to the degree of acid inhibition.

Clinical use of proton-pump inhibitors but not H2-blockers or antacid/alginates raises the serum levels of amidated gastrin-17, pepsinogen I and pepsinogen II in a random adult population

OBJECTIVE

Proton-pump inhibitors (PPIs), H(2) receptor antagonists (H(2)RAs) and antacids/alginates reduce intragastric acidity and may thus influence normal gastric physiology. The purpose of this study was to examine the effect of these compounds on serum levels of amidated gastrin-17 (G-17) and pepsinogens (PGI & PGII) in a large, random, adult Swedish population sample with uninfected stomach mucosa.

MATERIAL AND METHODS

The initial sample subjects (n=1000, mean age 50 years, range 20-80 years) completed a questionnaire on the use of acid inhibitory drugs 1 week and/or 3 months before study entry. All subjects (n=590) with normal gastric mucosa as delineated by serum biomarkers were included. Among them, serum levels of PGI, PGII and G-17 were compared between those who used acid inhibitory drugs and those who did not.

RESULTS

The serum levels of G-17 or pepsinogens in the subjects who reported use of H(2)RAs (n=18) or antacid/alginates (n=66) during the previous 3 months did not differ from those in non-users (n=471). However, the median levels of G-17 and pepsinogens were significantly (p<0.001) higher among the PPI users (n=35) than among non-users: the levels were approximately doubled. The ratio of PGI/PGII was, however, similar between PPI users and non-users, or those using antacids/alginates or H(2)RAs. Among subjects using PPIs, the serum levels of pepsinogens correlated positively (p<0.01) with the serum levels of G-17.

CONCLUSIONS

PPIs but not antacids/alginates or H(2)RAs markedly increase the fasting levels of serum amidated G-17 and pepsinogens among ordinary patients in everyday clinical practice.

On-demand therapy for gastroesophageal reflux disease

The following pages summarize the proceedings of a symposium held in May 2006 on the emerging role of on-demand therapy for gastroesophageal reflux disease (GERD). Medical therapy for GERD has undergone significant change in recent years with the advent of effective, but expensive, antisecretory agents. On-demand (patient-driven) therapy is attractive to payers and patients, because it appears to be both cost-effective and convenient. Many individuals appear to accept occasional symptomatic breakthrough in exchange for personal control of their disease. On-demand therapy should be distinguished from intermittent therapy, which is either patient- or physician-driven, but which requires intermittent episodes of continuous therapy followed by discontinuation until symptoms recur. Proton pump inhibitors appear to be effective on-demand agents despite theoretical pharmacodynamic limitations for this class of drug. The available data support the use of on-demand therapy for GERD in uninvestigated reflux disease, nonerosive reflux disease, and possibly mild esophagitis as well. On-demand therapy should not be considered for patients with severe esophagitis.

Systematic review: Rebound acid hypersecretion after therapy with proton pump inhibitors

BACKGROUND

The occurrence and the clinical relevance of rebound acid hypersecretion after discontinuation of proton pump inhibitors is unclear.

AIM

To perform a systematic review of rebound acid hypersecretion after discontinuation of proton pump inhibitors.

METHODS

PubMed, Embase and Central were searched up to October 2005 with indexed terms.

RESULTS

Eight studies were included, sample size was 6-32. The studies used both basal and stimulated acid output as parameters to study rebound acid hypersecretion and assessed these at different time points and with variable methods. Five studies (including four randomized studies) did not find any evidence for rebound acid hypersecretion after proton pump inhibitor therapy. Of the remaining three studies, the duration of proton pump inhibitor therapy was the longest and two of these studies were the only to assess Helicobacter pylori status of their study subjects. These two studies suggested that rebound acid hypersecretion may occur in H. pylori-negatives after 8 weeks of proton pump inhibitors.

CONCLUSIONS

Studies that have investigated rebound acid hypersecretion after cessation of proton pump inhibitor treatment are heterogenic in design, methods and outcome. There is some evidence from uncontrolled trials for an increased capacity to secrete acid in H. pylori-negative subjects after 8 weeks of treatment. There is no strong evidence for a clinically relevant increased acid production after withdrawal of proton pump inhibitor therapy.

Consequences of long-term proton pump blockade: insights from studies of patients with gastrinomas

Proton pump inhibitors are being increasingly used and for longer periods of time, especially in patients with gastroesophageal reflux disease. Each of these trends has led to numerous studies and reviews of the potential risk-benefit ratio of the long-term use of proton pump inhibitors. Both long-term effects of hypergastrinaemia due to the profound acid suppression caused by proton pump inhibitors as well as the effects of hypo-/achlorhydria per se have been raised and studied. Potential areas of concern that have been raised in the long-term use of proton pump inhibitors, which could alter this risk-benefit ratio include: gastric carcinoid formation; the development of rebound acid hypersecretion when proton pump inhibitor treatment is stopped; the development of tolerance; increased oxyntic gastritis in H. pylori patients and the possibility of increasing the risk of gastric cancer; the possible stimulation of growth of non-gastric tumours due to hypergastrinaemia; and the possible effect of the hypo/achlorhydria on nutrient absorption, particularly iron and vitamin B12. Because few patients with idiopathic gastro-oesophageal reflux disease/peptic ulcer disease have been treated long-term (i.e., >10 years), there is little known to address the above areas of potential concern. Most patients with gastrinomas with Zollinger-Ellison syndrome have life-long hypergastrinaemia, require continuous proton pump inhibitors treatment and a number of studies report results of >5-10 years of tratment and follow-up. Therefore, an analysis of Zollinger-Ellison syndrome patients can provide important insights into some of the safety concerns raised above. In this paper, results from studies of Zollinger-Ellison syndrome patients and other recent studies dealing with the safety concerns above, are briefly reviewed.

Rebound hypersecretion after inhibition of gastric acid secretion

Drugs inhibiting gastric acid secretion are widely used because of the high prevalence of acid-related disorders. However, from clinical experience it seems that symptom relapse is common after withdrawal of these drugs. Experimental as well as clinical studies have demonstrated an increased acid secretion after a period of treatment with either histamine 2 receptor antagonists or proton pump inhibitors. Rebound hypersecretion is likely to reflect the following sequence of events: Long-term inhibition of acid output is accompanied by elevated serum gastrin levels, leading to enterochromaffin-like cell activation and proliferation, resulting in increased amounts of histamine being mobilized from these cells to stimulate the parietal cells. The clinical consequences of rebound hypersecretion have not been settled.

Long-term safety of proton pump inhibitors: risks of gastric neoplasia and infections

After Helicobacter pylori eradication was introduced and largely eliminated the need for maintenance therapy for peptic ulcer disease, gastroesophageal reflux disease (GERD) became the main indication for prolonged gastric acid inhibition. The drug effect on GERD depends on the degree of acid inhibition, thus the efficacious proton pump inhibitors are preferred. The proton pump inhibitors have few immediate side effects, the main concern being the profound hypoacidity and hypergastrinaemia they induce. In short-term, hypergastrinaemia causes rebound hyperacidity, possibly worsening GERD and reducing the efficacy of histamine H(2) blockers. In the long-term, hypergastrinaemia causes enterochromaffin-like cell hyperplasia and carcinoids. Since enterochromaffin-like cells may be important in gastric carcinogenesis, iatrogenic hypergastrinaemia may predispose to carcinoma. Gastric hypoacidity also increases gut bacterial infections, and the barrier function of acid against viral and prion infections requires further assessment.

Nonprescription doses of ranitidine are effective in the relief of episodic heartburn

BACKGROUND

Many Americans have heartburn or related symptoms monthly and >20% experience heartburn at least once per day. Although many self-treat episodic heartburn with nonprescription antacids, newer treatments that decrease gastric volume and increase the pH of refluxed material are proving effective and popular in relieving heartburn.

AIM

To evaluate the safety and efficacy of low-dose regimens of ranitidine for the relief of heartburn.

METHODS

Adults with at least a 3-month history of heartburn were eligible for this randomized, double-blind, parallel group, multicenter dose-ranging study. Following a 1-week, open-label run-in phase to document baseline heartburn frequency, subjects were randomly assigned to receive treatment with one tablet of either ranitidine, 75 mg (n = 537); ranitidine, 25 mg (n = 539); or placebo (n = 544), to be taken as needed up to four times daily for 2 weeks for the relief of heartburn.

RESULTS

The ranitidine 75-mg regimen was statistically (P < 0.05) and clinically (as defined a priori as > or =10% improvement) more effective than placebo in relieving episodic heartburn and in reducing antacid consumption. Ranitidine, 25 mg, was also statistically superior (P < 0.05) to placebo in providing heartburn relief. In addition, both regimens were superior to placebo in providing heartburn relief within 30 to 45 minutes of dosing. Ranitidine continued to be as effective over placebo in the treatment of the last heartburn episode as in the treatment of the first heartburn episode. Ranitidine was also equally effective over placebo in the treatment of mild, moderate, and severe episodes of heartburn. Ranitidine, 75 mg, was statistically superior to placebo for the relief of nocturnal heartburn episodes, whereas ranitidine, 25 mg, was not. All treatments were well tolerated and adverse events occurred no more frequently with the ranitidine regimens than with placebo.

CONCLUSIONS

Low-dose ranitidine provides prompt and lasting relief of heartburn and has a safety profile comparable to that of placebo.

Does short-term treatment with proton pump inhibitors cause rebound aggravation of symptoms?

BACKGROUND

Rebound acid hypersecretion might occur after treatment with proton pump inhibitors. This study looks for a rebound aggravation of symptoms after short-term treatment with lansoprazole.

STUDY

Sixty-two patients (19 men and 43 women; mean age, 54 years; range, 32-77 years) with heartburn and regurgitation and normal upper endoscopy findings were studied in a randomized, double-blind, placebo-controlled trial with a crossover design. There were two 5-day treatment periods with lansoprazole 60 mg once daily or placebo in random order, separated by a 9-day washout period. Reflux, total, and antacid scores were calculated for each of the treatment periods. Higher scores during the placebo period in the group given lansoprazole first than in the group given placebo first indicated a rebound aggravation of symptoms.

RESULTS

The mean symptom scores during the placebo period in the groups given lansoprazole first and placebo first were as follows: reflux score, 21.5 and 17.6, respectively (not significant); total score, 11.2 and 10.3, respectively (not significant); and antacid score, 8.2 and 7.2, respectively (not significant).

CONCLUSIONS

There is no indication of a rebound aggravation of symptoms 12 to 14 days after a 5-day treatment with lansoprazole 60 mg once daily in patients with reflux symptoms.

Problems related to acid rebound and tachyphylaxis

Rebound acid hypersecretion after taking histamine H(2)-receptor antagonists is a now well-established class phenomenon. It has been demonstrated both basally and in response to meal and gastrin-releasing peptide stimulation, but not in response to peak pentagastrin stimulation. It is present by 3 days after treatment but has resolved by 10 days. A recent study in previously asymptomatic healthy volunteers has suggested that this phenomenon may be clinically relevant. Tachyphylaxis/tolerance after the use of H(2)-receptor antagonists is also now well established. It manifests as a loss of acid inhibitory efficacy and is also a class effect. It is present within a few doses but is not progressive after 29 days. Rebound acid hypersecretion after proton pump inhibitors has been shown for both basal and maximal acid output by 14 days after treatment. It is found in Helicobacter pylori -negative, but not positive, subjects, probably owing to the influence of the enhanced oxyntic gastritis that occurs during proton pump inhibitor therapy. It is a prolonged phenomenon, lasting for at least 2 months after a 2-month treatment course. This duration is likely to reflect its development as a result of trophic effects on the oxyntic mucosa. This trophism is caused by the marked hypergastrinaemia that occurs secondary to the profound acid suppression during proton pump inhibitor treatment. The clinical relevance of this phenomenon remains at present unknown. Tachyphylaxis/tolerance has not yet been shown in several short-term studies after taking proton pump inhibitors. A recent clinical study has, however, suggested that this phenomenon may merit longer-term evaluation.

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 prescribing of acid suppressants prior to the endoscopic diagnosis of Barrett's oesophagus and oesophagitis

BACKGROUND

There has been a dramatic rise in incidences of Barrett's oesophagus and oesophageal adenocarcinoma. It has been suggested that the introduction and use of acid suppression therapy may be a factor in the rising incidences of Barrett's oesophagus and oesophageal adenocarcinoma.

METHODS

This was a record linkage study, using a prescribing database and an endoscopy database. Patients who had undergone their first endoscopy during the period 1992-1995 and received the diagnosis of Barrett's oesophagus or oesophagitis were identified. The prescribing of acid suppressants was compared for the 3 years prior to endoscopy, between those with Barrett's oesophagus and those with oesophagitis.

RESULTS

There was no significant difference between the Barrett's patients and the oesophagitis patients in the proportion that had been exposed to acid suppression therapy (53.4% vs. 51.7%, P=0.704). The mean number of days of prescribing among those who had been exposed to acid suppression therapy was higher in the Barrett's group (340.5 vs. 237.0 days, P=0.001).

CONCLUSIONS

Patients with Barrett's oesophagus have received more acid suppressant therapy prior to diagnosis. The reasons for this are not clear. However, 46.6% of Barrett's patients have not been exposed to acid suppressant therapy.

Duration of effect of lansoprazole on gastric pH and acid secretion in normal male volunteers

AIM

A double-blind, placebo-controlled study to assess the duration of effect of lansoprazole 30 mg o.m. on intragastric pH, acid secretion, gastrin levels, the potential for rebound acidity, and the relationship between gastric acid and drug pharmacokinetic parameters.

METHODS

Sixteen subjects were treated with lansoprazole 30 mg daily or placebo for 14 days, followed by a 7-day post-dosing period and a post-study evaluation on day 28. Ambulatory 24-h pH was recorded and pentagastrin-stimulated acid secretion measured. Plasma kinetics of lansoprazole were determined.

RESULTS

Mean intragastric pH in the lansoprazole group increased significantly (P < 0.05) from baseline to day 14 compared to placebo. After cessation of treatment, secretory activity, as measured by intragastric pH, basal acid output and stimulated acid output, returned to baseline in 2 to 4 days without any overshoot, indicating the absence of acid rebound. Lansoprazole's terminal disposition half-life was 1.11 h. Mean pH and serum gastrin returned to baseline with half-lives of 22 and 19 h, respectively.

CONCLUSIONS

Lansoprazole 30 mg daily significantly increases mean intragastric pH without producing acid rebound. Regeneration of acid production depends primarily on de novo synthesis of the acid pump.

Gastroesophageal reflux: practical management of a common, challenging disorder

Gastroesophageal reflux (GER) occurs in 2 distinct forms that differ in pathophysiology, clinical presentation, natural history, and therapy: mild GER (with no or minimal esophagitis) and classic, severe reflux (at risk for erosive esophagitis). A minority of subjects (< 20%) have the classic, potentially severe pattern of GER caused by reduced lower esophageal sphincter (LES) pressure and prolonged acid reflux, particularly at night, but also during the day. Evaluation and management must be catered to patients with this pattern of reflux. In contrast, symptoms in mild reflux (the majority) often occur during the day after meals in an upright posture (upright reflux); resting LES pressure is usually normal (reflux episodes are related to transient relaxation of the LES) and little reflux occurs at night. Acid reflux, which occurs mostly during the day, overlaps with the normal range and esophagitis is rare; however, symptoms can be distressing. Optimal management is controversial because no outcome trials have been conducted to address management in primary care settings. However, clinical clues can help differentiate mild and severe reflux and guide management decisions. This article provides a detailed approach to current management of GER syndromes.

Rebound hypersecretion after omeprazole and its relation to on-treatment acid suppression and Helicobacter pylori status

BACKGROUND & AIMS

There have been conflicting reports regarding acid secretion after treatment with omeprazole. This study examined acid secretion after treatment with omeprazole and its relation to Helicobacter pylori status and on-treatment gastric function.

METHODS

Twelve H. pylori-negative and 9 H. pylori-positive subjects were examined before, on, and at day 15 after an 8-week course of 40 mg/day omeprazole. On each occasion, plasma gastrin, intragastric pH, and acid output were measured basally and in response to increasing doses of gastrin 17.

RESULTS

In the H. pylori-negative subjects at day 15 after omeprazole treatment, basal acid output was 82% higher (P < 0.007) and maximal acid output 28% higher (P < 0.003) than before omeprazole. The degree of increase in maximal acid output was related to both on-treatment pH and on-treatment fasting gastrin levels, being 48.0% in subjects with an on-treatment pH of >4 vs. 21. 0% in those with a pH of <4 (P < 0.02) and 49.2% in subjects with an on-treatment gastrin of >25 ng. L-1 vs. 19.8% in those with a fasting gastrin of <25 ng. L-1 (P < 0.006). At day 15 after omeprazole treatment, the H. pylori-positive subjects showed a heterogeneous response with some having increased acid output and others persisting suppression.

CONCLUSIONS

Rebound acid hypersecretion occurs in H. pylori-negative subjects after omeprazole treatment. Its severity is related to the degree of elevation of pH on treatment. Persisting suppression of acid secretion masks the phenomenon in H. pylori-positive subjects.

The effect of cisapride in maintaining symptomatic remission in patients with gastro-oesophageal reflux disease

BACKGROUND

Successful treatment of gastro-oesophageal reflux disease (GORD) has traditionally been assessed as healing of reflux oesophagitis, which may not be relevant in patients with moderate disease. In these patients symptom relief and patient satisfaction with therapy are of fundamental importance. Cisapride has well-documented prokinetic effects and may be well suited for long-term therapy of GORD, but its effectiveness in purely symptomatic treatment is unknown. We therefore compared two dosage regimens of cisapride with placebo over a period of 6 months in patients with evidence of gastrooesophageal reflux, initially treated with antisecretory medication, with regard to maintaining symptom relief and satisfaction with treatment.

METHODS

Five hundred and thirty-five patients with reflux oesophagitis grade 1 (n = 293) or 2 (n = 124) or with no reflux oesophagitis but pathologic 24-h pH-metry (n = 118) achieved satisfactory symptom relief with an H2-receptor antagonist or proton pump inhibitor within 4-8 weeks. In a double-blind randomized, parallel-group study, they were then treated with cisapride, 20 mg at night or 20 mg twice daily, or placebo and followed up for a maximum period of 6 months. Relapse was defined as dissatisfaction with therapy or an average consumption of more than two antacid tablets a day.

RESULTS

Median time to relapse was 63 days for cisapride, 20 mg twice daily; 59 days for cisapride, 20 mg at night; and 49 days for placebo. Time to relapse was not significantly different (P = 0.09). Presence and grade of oesophagitis at base line, type of therapy before randomization, and pattern of non-reflux symptoms at base line did not influence these findings significantly.

CONCLUSION

The study indicates that cisapride is of limited value in maintenance therapy of GORD in patients in whom symptom relief has been accomplished with potent antisecretory medication. This 'step-down' approach to therapy seems disadvantageous in the long-term therapy of GORD.

Marked increase in gastric acid secretory capacity after omeprazole treatment

BACKGROUND

In contrast with the histamine2 (H2) blockers, proton pump inhibitors have not been shown to give rebound hypersecretion of acid. Taking into consideration the hyperplasia of the enterochromaffin-like (ECL) cell provoked by hypergastrinaemia secondary to profound acid inhibition and the central role of histamine from ECL cells in the regulation of acid secretion, the lack of any rebound acid hypersecretion after treatment with proton pump inhibitors has been questioned.

AIMS

To reassess the effect of treatment with omeprazole on post-treatment acid secretion.

METHODS AND PATIENTS

Basal and pentagastrin stimulated acid secretion were determined in nine patients with reflux oesophagitis before and 14 days after termination of a 90 day treatment period with the proton pump inhibitor omeprazole (40 mg daily). Basal gastrin release were determined before and during omeprazole treatment. Furthermore, biopsy samples from the oxyntic mucosa were taken before and at the end of the treatment period for chemical (histamine and chromogranin A (CgA)) evaluation of the ECL cell mass.

RESULTS

A substantial increase in meal stimulated gastrin release during omeprazole treatment resulted in an increased ECL cell mass. Furthermore, CgA in serum increased during omeprazole treatment suggesting that serum CgA may be used as a test to evaluate ECL cell hyperplasia. A significant increase in basal and a marked (50%) and significant increase in pentagastrin stimulated acid secretion were found after treatment with omeprazole.

CONCLUSIONS

Increased acid secretion after a conventional treatment period with a proton pump inhibitor is probably due to ECL cell hyperplasia and may have negative consequences for acid related diseases.

Bacterial overgrowth during treatment with omeprazole compared with cimetidine: a prospective randomised double blind study

BACKGROUND

Gastric and duodenal bacterial overgrowth frequently occurs in conditions where diminished acid secretion is present. Omeprazole inhibits acid secretion more effectively than cimetidine and might therefore more frequently cause bacterial overgrowth.

AIM

This controlled prospective study compared the incidence of gastric and duodenal bacterial overgrowth in patients treated with omeprazole or cimetidine.

METHODS

47 outpatients with peptic disease were randomly assigned to a four week treatment regimen with omeprazole 20 mg or cimetidine 800 mg daily. Gastric and duodenal juice were obtained during upper gastrointestinal endoscopy and plated for anaerobic and aerobic organisms.

RESULTS

Bacterial overgrowth (> or = 10(5) cfu/ml) was present in 53% of the patients receiving omeprazole and in 17% receiving cimetidine (p < 0.05). The mean (SEM) number of gastric and duodenal bacterial counts was 6.0 (0.2) and 5.0 (0.2) respectively in the omeprazole group and 4.0 (0.2) and 4.0 (0.1) in the cimetidine group (p < 0.001 and < 0.01; respectively). Faecal type bacteria were found in 30% of the patients with bacterial overgrowth. Basal gastric pH was higher in patients treated with omeprazole compared with cimetidine (4.2 (0.5) versus 2.0 (0.2); p < 0.001) and in patients with bacterial overgrowth compared with those without bacterial overgrowth (5.1 (0.6) versus 2.0 (0.1); p < 0.0001). The nitrate, nitrite, and nitrosamine values in gastric juice did not increase after treatment with either cimetidine or omeprazole. Serum concentrations of vitamin B12, beta carotene, and albumin were similar before and after treatment with both drugs.

CONCLUSIONS

These results show that the incidence of gastric and duodenal bacterial overgrowth is considerably higher in patients treated with omeprazole compared with cimetidine. This can be explained by more pronounced inhibition of gastric acid secretion. No patient developed signs of malabsorption or an increase of N-nitroso compounds. The clinical significance of these findings needs to be assessed in studies with long-term treatment with omeprazole, in particular in patients belonging to high risk groups such as HIV infected and intensive care units patients.

Patterns of 24-hour oesophageal acid exposure after acute withdrawal of acid suppression

AIM

To measure 24-h ambulatory oesophageal pH data in patients with gastro-oesophageal reflux disease prior to, during and after acute treatment with comparable doses of omeprazole and ranitidine.

METHODS

The subjects were 20 adults with at least 8% acid contact time. Ten subjects were treated for 1 week with omeprazole 20 mg q.d.s. and 10 subjects with ranitidine 300 mg t.d.s. All subjects were examined at the end of 1 week of therapy and subsequent to cessation of treatment (1 day for ranitidine and 3 days for omeprazole).

RESULTS

Both drugs produced a statistically significant (P < 0.05) decrease in acid contact time with acute treatment. Omeprazole produced a significantly greater decrease in acid contact time when compared to ranitidine. Subsequent to treatment cessation, the total acid contact time for omeprazole remained significantly less than the baseline level, while ranitidine returned to levels which were not significantly different from the baseline.

CONCLUSION

These data provide no evidence for a 'reflux rebound' subsequent to the cessation of acute acid secretory suppression.

Effects of ranitidine on gastric vesicles containing H+,K(+)-adenosine triphosphatase in rats

BACKGROUND

To ascertain the mechanism for rebound acid hypersecretion after treatment with an H2-receptor blocker, we investigated the effects of ranitidine on gastric H+,K(+)-adenosine triphosphatase (ATPase) in rats.

METHODS

Male Wistar rats received ranitidine (1-50 mg/kg body weight intraperitoneally twice a day for 5 days). The rats were starved for 15 h after the last treatment and then killed, and gastric vesicles containing H+,K(+)-ATPase were prepared.

RESULTS

Treatment with ranitidine dose-dependently increased protein content in the gastric vesicular fraction purified from the gastric mucosa without changing total protein content. Ranitidine also increased the content of a 94,000-dalton protein, the catalytic subunit of H+,K(+)-ATPase. On the other hand, ranitidine did not affect the specific activity of the enzyme (mumol/min/mg of the gastric vesicular protein). Since gastric vesicles in the fasting state mainly consist of the tubulovesicular membrane, these results suggest that ranidine administration increases total tubulovesicular H+,K(+)-ATPase content (mumol/min/rat) by increasing the number of tubulovesicles per parietal cell. The ranitidine-induced increase in total tubulovesicular H+,K(+)-ATPase activity was still evident 1 week after treatment and returned to control level 1 month later.

CONCLUSIONS

All these findings suggest that the increased content and total activity of tubulovesicular H+,K(+)-ATPase after ranitidine treatment may contribute to the mechanism for acid rebound after H2-blocker therapy.

Treatment of peptic ulcers from now to the millennium

The present strategies for the management of peptic ulceration are well tolerated and clinically effective. Histamine H2-receptor antagonists can be used for mild to moderate disease, and proton pump inhibitors are of particular benefit for patients with severe peptic ulceration and the Zollinger-Ellison syndrome. However, none of these treatments provides protection against recurrent ulceration, except when taken as long-term continuous treatment. Long-term exposure to pharmacological agents raises problems of safety, particularly relating to a lack of intragastric acidity. In addition, the accelerated development of atrophic gastritis in patients receiving omeprazole requires investigation and assessment. It is unlikely that there will be any major development in the area of control of gastric acid secretion, except perhaps the introduction of specific immunization against gastrin. However, the clinical benefit of this strategy awaits assessment. The main area for development must be the introduction of convenient and effective regimens for the eradication of Helicobacter pylori infection. Existing regimens are either simpler and relatively ineffective, or too complicated for widespread application. Bearing in mind the long gestation period of any new drug, it seems likely that the only innovative drug that will be introduced for the management of peptic ulceration before the millennium will be ranitidine bismuth citrate, an antisecretory anti-H. pylori drug that will usually be used in combination with an antibiotic.

Duodenal bacterial overgrowth during treatment in outpatients with omeprazole

The extent of duodenal bacterial overgrowth during the pronounced inhibition of acid secretion that occurs with omeprazole treatment is unknown. The bacterial content of duodenal juice of patients treated with omeprazole was therefore examined in a controlled prospective study. Duodenal juice was obtained under sterile conditions during diagnostic upper endoscopy. Aspirates were plated quantitatively for anaerobic and aerobic organisms. Twenty five outpatients with peptic ulcer disease were investigated after a 5.7 (0.5) weeks (mean (SEM)) treatment course with 20 mg (nine patients) or 40 mg (16 patients). The control group consisted of 15 outpatients referred for diagnostic endoscopy without prior antisecretory treatment. No patient in the control group had duodenal bacterial overgrowth. In the omeprazole group bacterial overgrowth (> or = 10(5) cfu/ml) was found in 14 (56%) patients (p = 0.0003). The number of bacteria (log10) in duodenal juice in patients treated with omeprazole was distinctly higher (median 5.7; range < 2-8.7) when compared with the control group (median < 2; range < 2-5.0; p = 0.0004). As well as orally derived bacteria, faecal type bacteria were found in seven of 14 and anaerobic bacteria in three of 14 patients. Bacterial overgrowth was similar with the two doses of omeprazole. These results indicate that duodenal bacterial overgrowth of both oral and faecal type bacteria occurs often in ambulatory patients treated with omeprazole. Further studies are needed to determine the clinical significance of these findings, particularly in high risk groups during long term treatment with omeprazole.

Gastric acid secretion and intragastric acidity: measurement in health and disease

Gastric acid secretion tests have limited use in clinical practice. For practical purposes, a pH measurement on a fasting gastric aspirate will provide strong evidence of the presence or absence of achlorhydria. Tests of gastric acidity, in particular 24-h acidity studies, have provided considerable insight into normal and abnormal gastric physiology, and have largely determined the dosing regimens for the management of acid-peptic diseases. Acid tests may be simple to perform, so much so that they have been suggested as 'practicals' for student teaching (Nicol et al, 1991). However, reproducible and meaningful results require careful attention to detail, and the appropriate mathematical analysis is still subject to some debate. It is important that the presentation of the data should allow the reader to assess the response over the 24-h period, and also the range of individual responses. Despite the many years of research into gastric acid secretion, only recently have the effects of age, sex, diet, smoking and mental stress been identified. In addition, many data need to be reviewed in the light of the effects of H. pylori infection on gastrin release. H2-receptor antagonists had been studied extensively before and since their first clinical use in 1974, but surprisingly only recently have the issues of tolerance and rebound been defined. The 24-h intragastric acidity profile remains an essential study before the start of clinical trials on any new drug to be used for the treatment of acid-peptic diseases.

Does the stomach adapt to Helicobacter pylori?

To shed some light on the question of gastric adaptation to Helicobacter pylori infection, an overview is given of the various histopathological and clinical consequences of H. pylori infection in man. H. pylori infection can be considered as a chronic bacterial infection. For many individuals there is a balance between a low degree of infection and a low degree of inflammation. The microbial or host factors in adaptation of this balance are largely unknown. If and how 'downregulation' of the inflammatory/immune response does occur need further study.

Acid secretion, 1932-92: advances, adaptations, and paradoxes

This paper reviews the evolution of our understanding of various aspects of gastric acid secretion over the past 60 years. Embryologic aspects and neonatal acid secretion are considered, and the relationship between parietal cell mass and acid secretion and the changing concepts of parietal cell activation are discussed. The effect of aging on acid secretion and the relevance of acid secretion in health and disease are reviewed, and current views on adaptation to therapeutic inhibition of acid secretion presented. The aetiologic link between acid secretion and ulcer disease is re-examined, and the role of pepsin, growth factors, and Helicobacter pylori briefly considered.

Rebound intragastric hyperacidity after abrupt withdrawal of histamine H2 receptor blockade

In a series of 24 hour studies, intragastric acidity and plasma gastrin concentration were measured simultaneously in 46 healthy subjects before, during, and 24 to 48 hours after abrupt withdrawal of a histamine H2 receptor antagonist regimen. For 34 days subjects were given either cimetidine 800 mg at night (n = 8), ranitidine 150 mg twice daily (n = 10), ranitidine 300 mg at night (n = 12), nizatidine 300 mg at night (n = 8), or famotidine 40 mg at night (n = 8). All subjects responded to H2 blockade by a decrease in 24 hour intragastric acidity. Withdrawal of H2 blockade resulted in a significant rise in median nocturnal integrated intragastric acidity in 42 of 46 subjects (+36%; 95% CI +19, +55%) compared with prestudy values, but this rise was not associated with a significant change in the median integrated plasma gastrin concentration (+1%; 95% CI -12, +13%). A statistically significant rise in nocturnal acidity was observed after all regimens, except after dosing with famotidine. After stopping, median daytime integrated acidity and plasma gastrin concentrations in the whole group were raised, but not significantly: values were +15% (95% CI +4, +34%) and +5% (95% CI -2, +12%), respectively. A statistically significant increase in daytime acidity was observed only after dosing with ranitidine. In conclusion, intragastric hyperacidity occurs in most subjects after abrupt withdrawal of a histamine H2 receptor blocker, but this phenomenon is not associated with hypergastrinaemia.

Rebound hypersecretion after H2-antagonist withdrawal--a comparative study with nizatidine, ranitidine and famotidine

Our previous study demonstrated rebound nocturnal acid hypersecretion after a 4-week course of nizatidine. Nocturnal acid output was increased by 77% two days after discontinuing treatment compared with pretreatment values. To confirm this effect with other H2-blockers we assessed daytime intragastric pH, fasting and meal-stimulated plasma gastrin and nocturnal acid output in 9 duodenal ulcer patients in remission before, during and two days after treatment with three different drugs. Each patient received 4-week courses of 300 mg ranitidine, 40 mg famotidine or 300 mg nizatidine, taken at 20.00 hours in randomized order with a 'washout' period of 4 weeks between each course of drug. Median nocturnal acid output (mmol/10 h) decreased during treatment with ranitidine to 3 (range 0-17), famotidine to 4 (1-12) and nizatidine 6 (0-40) compared with the respective pre-treatment values, 49 (20-126; P less than 0.01), 52 (22-105; P less than 0.01) and 32 (23-114; P less than 0.01). Two days after discontinuing treatment nocturnal acid output was increased after ranitidine at 77 (28-237; P less than 0.04) and after nizatidine at 64 (17-130; P less than 0.05) compared with pre-treatment values. There was no significant change in nocturnal acid output after famotidine at 57 (27-107) compared with the pre-treatment value. There was no change in daytime intragastric pH with any drug during or after treatment compared with the pre-treatment values. Fasting and meal-stimulated plasma gastrin concentrations were increased on the final treatment day with ranitidine and famotidine but had returned to pretreatment levels two days after treatment. The rebound acid hypersecretion may contribute to the high ulcer relapse rate after discontinuation of H2-receptor antagonists.