Rebound nocturnal hypersecretion after four weeks treatment with an H2 receptor antagonist

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.

Acid Suppressive Drugs

Histamine H₂ receptor antagonists (H₂RAs) suppress gastric acid production by blocking H₂ receptors in parietal cells. Studies have shown that proton pump inhibitors (PPIs) are superior to H₂RAs as a treatment for acid-related disorders, such as peptic ulcer disease (PUD) and gastroesophageal reflux disease (GERD). PPIs reduce gastric acid production by irreversibly inhibiting the H⁺/K⁺ ATPase pump, and they also increase gastric emptying. Although PPIs have differing pharmacokinetic properties, each PPI is effective in managing GERD and PUDs. However, PPIs have some limitations, including short plasma half-lives, breakthrough symptoms (especially at night), meal-associated dosing, and concerns associated with long-term PPI use. Potassium-competitive acid blockers (P-CABs) provide more rapid and profound suppression of intragastric acidity than PPIs. P-CABs are non-inferior to lansoprazole in healing erosive esophagitis and peptic ulcers, and may also be effective in improving symptoms in patients with non-erosive reflux disease. Acid suppressive drugs are the most commonly used drugs in clinical practice, and it is necessary to understand the pharmacological properties and adverse effects of each drug.

Mitigation of Gastric Damage Using Cinnamomum cassia Extract: Network Pharmacological Analysis of Active Compounds and Protection Effects in Rats

Gastritis is a common disease worldwide that is caused by various causes such as eating habits, smoking, severe stress, and heavy drinking, as well as Helicobacter pylori infections and non-steroidal anti-inflammatory drugs. Cinnamomum cassia is a tropical aromatic evergreen tree commonly used as a natural medicine in Asia and as a functional food ingredient. Studies have reported this species' anti-obesity, anti-diabetic, and cardiovascular disease suppression effects. We evaluated the potential effects of C. cassia using non-steroidal anti-inflammatory drugs (NSAIDs), ethanol (EtOH), and ethanol/hydrochloric acid (HCl)-induced gastric mucosal injury models. C. cassia extracts reduced the area of gastric mucosa injury caused by indomethacin, NSAID, EtOH, and EtOH/HCl. We also applied a network pharmacology-based approach to identify the active compounds, potential targets, and pharmacological mechanisms of C. cassia against gastritis. Through a network pharmacology analysis, 10 key components were predicted as anti-gastritis effect-related compounds of C. cassia among 51 expected active compounds. The NF-κB signaling pathway, a widely known inflammatory response mechanism, comprised a major signaling pathway within the network pharmacology analysis. These results suggest that the anti-gastritis activities of C. cassia may be induced via the anti-inflammatory effects of key components, which suppress the inflammation-related genes and signaling pathways identified in this study.

Gastroprotective Effects of Cudrania tricuspidata Leaf Extracts by Suppressing Gastric cAMP and Increasing Gastric Mucins

Cudrania tricuspidata has been used as an East Asian folk remedy to treat various symptoms. Recently, scientific evidence of the efficacy of C. tricuspidata has emerged. The objective of this study was to elucidate protective role of C. tricuspidata in the gastric mucosa using pylorus-ligated Sprague-Dawley rats and primary parietal cells. C. tricuspidata ethanol extracts attenuated gastric mucosal damage, secretion, and juice acidity in pylorus-ligated rats; however, it did not affect expression of gastric acid-related genes [muscarinic acetylcholine receptor M3 receptor (M3R), histamine H2-receptors (H2R), and cholecystokinin-2/gastrin receptors (CCK2R)] or serum gastrin concentrations. Furthermore, extracts greatly reduced levels of gastric cyclic adenosine monophosphate (cAMP) and significantly increased mRNA levels of gastric-type mucins (MUC5AC and MUC6). To identify the mode of action of C. tricuspidata extract in regulating gastric acid secretion, intracellular cAMP and mRNA for H2R, M3R, and CCK2R were measured in primary parietal cells. mRNA levels of H2R, M3R, and CCK2R did not significantly differ following treatment with C. tricuspidata extract, whereas cAMP induced by the H2R-specific agonist was significantly decreased. C. tricuspidata may therefore reduce gastric acid secretion by inhibiting H2R activity rather than regulating mRNA expression. These finding suggest that ethanol extracts of C. tricuspidata inhibit H2R-related gastric acid secretion and increase gastric mucus to help prevent gastric mucosal damage. Therefore, C. tricuspidata extract has potential to be used in foods and medicines to prevent diseases related to gastric mucosal damage, such as gastritis and functional dyspepsia.

Can H2 -receptor upregulation and raised histamine explain an anaphylactoid reaction on cessation of ranitidine in a 19-year-old female? A case report

The anaphylactoid reaction described follows cessation of ranitidine in a 19-year-old female with the disease cluster: mast cell activation syndrome, hypermobile Ehlers-Danlos syndrome and postural tachycardia syndrome. Anaphylaxis can give wide-ranging symptoms from rhinorrhoea and urticaria to tachycardia and system-wide, life-threatening, anaphylactic shock. Individuals with a disorder of mast cell activation can experience many such symptoms. H2 receptor antagonists, such as ranitidine, are commonly prescribed in this population. A mechanism for the reaction is proposed in the context of ranitidine, as an inverse agonist, causing upregulation of H2 histamine receptors and raised histamine levels due to enzyme induction. This effect, following extended and/or high antihistamine dosing, may have implications for other individuals with a disorder of mast cell activation, such as mastocytosis or mast cell activation syndrome. There are potential policy and patient guidance implications for primary and secondary care with respect to cessation of H2 antagonists.

The Effect of H2 Receptor Antagonist in Acid Inhibition and Its Clinical Efficacy

The first histamine H₂ receptor antagonists (H₂RAs) were developed in the early 1970s. They played a dominant role in treating peptic ulcer disease and gastroesophageal reflux disease (GERD). H₂RAs block the production of acid by H⁺, K⁺-ATPase at the parietal cells and produce gastric luminal anacidity for varying periods. H₂RAs are highly selective, and they do not affect H1 receptors. Moreover, they are not anticholinergic agents. Sequential development of H₂RAs, proton pump inhibitors (PPIs), and discovery of Helicobacter pylori infection changed the paradigm of peptic ulcer disease with marked decrease of morbidity and mortality. PPIs are known to be the most effective drugs that are currently available for suppressing gastric acid secretion. Many studies have shown its superiority over H₂RAs as a treatment for acid-related disorders, such as peptic ulcer disease, GERD, and Zollinger-Ellison syndrome. However, other studies have reported that PPIs may not be able to render stomach achlorhydric and have identified a phenomenon of increasing gastric acidity at night in individuals receiving a PPI twice daily. These nocturnal acid breakthrough episodes can be eliminated with an addition of H₂RAs at night. The effectiveness of nighttime dose of H₂RA suggests a major role of histamine in nocturnal acid secretion. H₂RAs reduce secretion of gastric acid, and each H₂RA also has specific effects. For instance, nizitidine alleviates not only symptoms of GERD, but also provokes gastric emptying, resulting in clinical symptom improvement of functional dyspepsia. The aim of this paper was to review the characteristics and role of H₂RAs and assess the future strategy and treatment of upper gastrointestinal disease, including acid related disorders.

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.

Anti-gastritis and wound healing effects of Momordicae Semen extract and its active component

Momordicae Semen, Momordica cochinchinensis Springer (Cucurbitaceae), has long been known to effectively relieve boils, rheumatic pain, and hemorrhoids. In this study, we investigated whether Momordicae Semen extract (MSE) has anti-gastritis effects in various rodent models and also explored possible mechanisms for the gastroprotective effects of MSE. MSE provided remarkable protective effects, comparable to those of rebamipide, in ethanol- and diclofenac-induced acute gastritis. In addition, it has demonstrated protective effect in a Helicobacter pylori-insulted chronic gastritis model. MSE also showed wound healing effect on cutaneous injury of mice and stimulated calcitonin gene-related peptide and somatostatin receptors, which may be related to its anti-gastritis effects. In a single oral dose toxicity study, the approximate lethal dose of MSE was determined at >2000 mg/kg/day. The NOAEL was set to be 2000 mg/kg/day from the repeated oral dose toxicity study. Moreover, momordica saponin I, a major ingredient of MSE, treatment decreased gastric mucosa damage indices in the ethanol- and diclofenac-induced acute gastritis models. The results suggest that MSE could be a promising gastroprotective herbal medicine and momordica saponin I might be used as an active marker compound for MSE.

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.

[Guidelines of treatment for non-bleeding peptic ulcer disease]

Over the past century, since the introduction of non steroidal anti-inflammatory drugs (NSAID), antacid, histamine H2-receptor antagonists (H2RA), proton pump inhibitors (PPI), and discovery of Helicobacter pylori infection, the paradigm of peptic ulcer disease has changed with marked decrease in morbidity and mortality. However, peptic ulcer disease still occupies a position as a major health problem with increase of aged population and NSAIDs usage. In daily general practice, the management of peptic ulcer disease is directed according to the presence of bleeding or not. For non-bleeding peptic ulcer disease, proper acid suppression and the correction of underlying causes such as Helicobacter pylori infection and NSAID use is the main stay of treatment. Though a complete understanding of pathophysiology and a perfect treatment strategy are still a challenge, this guideline aims to provide practical recommendations based on evidences or consensus of experts through in-depth literature review and expert meeting.

Pharmacodynamic and pharmacokinetic evaluation of CS-526 in cynomolgus monkeys

In the present study, we evaluated the effect of the novel acid pump antagonist 7-(4-fluorobenzyloxy)-2,3-dimethyl-1-{[(1S,2S)-2-methylcyclopropyl]methyl}-1H-pyrrolo[2,3-d]pyridazine (CS-526) on the intragastric acidity of cynomolgus monkeys. The study was performed in a crossover manner with five male animals. CS-526 was administered orally or intravenously at doses of 3.0, 10 and 30 mg/kg, or 0.3, 1.0 and 3.0 mg/kg, respectively. The time period in which the intragastric pH was 4.0 or more (Time(pH > or = 4.0)) and the median pH were calculated for 24 h after the administration. The intragastric pH was elevated after CS-526 treatment. The Time(pH > or = 4.0) was increased in a dose-dependent manner (p = 0.0292) in the oral administration, and the median pH was also increased in a dose-dependent fashion (p = 0.0491) in the intravenous administration. The plasma concentration of CS-526 and its metabolite R-130185 was increased after oral and intravenous administration of CS-526, except for one animal which did not show any detectable amount of R-130185 after intravenous administration at the lowest dose. The area under the time-concentration curve of the active component was increased in the dose proportional manner after oral and intravenous administration. The absolute bioavailability of the active component was estimated to be approximately 1%. Correlation between the pharmacodynamic parameters and the pharmacokinetic parameters was observed in oral (p = 0.0029-0.0745), but not in intravenous administration (p = 0.0558-0.2789). In conclusion, oral and intravenous administration of CS-526 showed inhibition on gastric acidity in cynomolgus monkeys using intragastric pH-metry and some pharmacokinetic and pharmacodynamic parameters were well correlated.

Physiological and clinical significance of enterochromaffin-like cell activation in the regulation of gastric acid secretion

Gastric acid plays an important role in digesting food (especially protein), iron absorption, and destroying swallowed micro-organisms. H+ is secreted by the oxyntic parietal cells and its secretion is regulated by endocrine, neurocrine and paracrine mechanisms. Gastrin released from the antral G cell is the principal physiological stimulus of gastric acid secretion. Activation of the enterochromaffin-like (ECL) cell is accepted as the main source of histamine participating in the regulation of acid secretion and is functionally and trophically controlled by gastrin, which is mediated by gastrin/CCK-2 receptors expressed on the ECL cell. However, long-term hypergastrinemia will induce ECL cell hyperplasia and probably carcinoids. Clinically, potent inhibitors of acid secretion have been prescribed widely to patients with acid-related disorders. Long-term potent acid inhibition evokes a marked increase in plasma gastrin levels, leading to enlargement of oxyntic mucosa with ECL cell hyperplasia. Accordingly, the induction of ECL cell hyperplasia and carcinoids remains a topic of considerable concern, especially in long-term use. In addition, the activation of ECL cells also induces another clinical concern, i.e., rebound acid hypersecretion after acid inhibition. Recent experimental and clinical findings indicate that the activation of ECL cells plays a critical role both physiologically and clinically in the regulation of gastric acid secretion.

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.

Rebound acid hypersecretion after long-term inhibition of gastric acid secretion

BACKGROUND

Rebound acid hypersecretion develops after the use of acid inhibitors.

AIM

To estimate the duration of hypersecretion and to elucidate the role of the enterochromaffin-like (ECL) cell in rebound acid hypersecretion.

METHODS

Patients waiting for anti-reflux surgery who had used a proton pump inhibitor daily > 1 year were included. All patients discontinued taking acid inhibiting drugs after the operation. Basal and pentagastrin stimulated acid output was measured at 4, 8, 16 and 26 weeks postoperatively. Oxyntic mucosal biopsies were collected before and 26 weeks after the operation for counting of histidine decarboxylase (HDC) immunoreactive cells. Serum chromogranin A (CgA) and gastrin were measured before and at 4, 8, 16 and 26 weeks after the operation.

RESULTS

Pentagastrin stimulated acid secretion was higher at 4 and 8 weeks than at 26 weeks after the operation. Gastrin and CgA were significantly reduced at 4 and 8 weeks, respectively. The number of HDC immunoreactive cells was reduced by 60% at 26 weeks postoperative.

DISCUSSION

Rebound acid hypersecretion lasts more than 8 weeks, but less than 26 weeks after long-term proton pump inhibition.

CONCLUSION

The findings indicate that not only the parietal cell mass, but also ECL cell mass and activity are involved in the mechanism of acid hypersecretion.

Review article: diagnosis and management of night-time reflux

Symptoms of gastro-oesophageal reflux disease (GERD) range from mild to severe and, when they occur during night-time hours, can interfere with sleep patterns and reduce overall quality of life. The clinical presentation of GERD is characterized by oesophageal as well as supra-oesophageal symptoms, including otolaryngologic and pulmonary complications. However, GERD may be overlooked as the cause of a patient's supra-oesophageal symptoms because these complaints can occur in the absence of oesophageal symptoms or endoscopic changes. The role of available tools used for GERD diagnosis, including endoscopy, oesophageal pH monitoring and an empirical course of proton pump inhibitor therapy, is discussed. Interventions available to achieve the therapeutic goals of symptom relief and prevention include specific lifestyle modifications and over-the-counter as well as prescription pharmacological agents. Patient-initiated, as-needed treatment may not be the best choice for managing persistent night-time reflux because it requires patient arousal from sleep. Proton pump inhibitor therapy remains the treatment of choice for patients with more severe symptoms and those with erosive oesophagitis. Few studies have specifically evaluated the role of pharmacological agents in the management of night-time reflux and comparisons are difficult due to the variability in study design and endpoints assessed.

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.

History of Acid Suppression: Focus on the Hospital Setting

In the hospital setting, prophylactic acid suppression is an important part of care for many critically ill patients. It may also prevent rebleeding in patients admitted with acute upper gastrointestinal tract bleeding. Effective treatments for these conditions stemmed from our increased understanding of the gastric acid secretory pathway and target pH values. The late 1970s saw the introduction of histamine2-receptor antagonists (H2RAs), which partially suppress basal and meal-stimulated acid secretion. Some of these agents can induce an intragastric pH greater than 3, lasting for approximately 10 hours/day when given twice/day at recommended doses. This level of acid suppression can facilitate healing of duodenal ulcers but has limited efficacy for other indications (e.g., gastrointestinal bleed). In the late 1980s a more potent class of acid-suppressing agents was developed, proton pump inhibitors (PPIs). The PPIs can induce an intragastric pH above 3 lasting for approximately 17 hours/day, and an intragastric pH above 5 for approximately 9 hours/day after once-daily oral administration of recommended doses. It is possible to attain even higher target pH values with large doses and with continuous intravenous infusion. Thus, PPIs are agents of choice for treatment of many acid-related disorders including peptic ulcer disease and moderate-to-severe gastroesophageal reflux disease, and for prevention of rebleeding in patients with upper gastrointestinal bleeding. Availability of an intravenous formulation, pantoprazole, enables hospitalized patients for whom oral administration is not feasible to benefit from the superior potency of PPIs. Preliminary data suggest that intravenous PPIs may be more effective than H2RA prophylaxis against stress-related ulcer bleeding for intensive care patients and should facilitate healing in those with bleeding ulcers of the upper gastrointestinal tract.

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.

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.

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.

Dyspepsia on withdrawal of ranitidine in previously asymptomatic volunteers

OBJECTIVE

H2 receptor antagonist therapy has been shown to produce rebound acid hypersecretion. The clinical significance of this phenomenon is not known. We performed this study to determine whether withdrawal of H2 receptor antagonist therapy results in dyspepsia in previously asymptomatic volunteers.

METHODS

Thirty-five Helicobacter pylori-positive asymptomatic volunteers were randomized in double-blind fashion to receive 2 months' treatment with either ranitidine 300 mg nocte or placebo. Dyspeptic symptoms were measured before starting treatment and over the course of 10 days after stopping treatment by means of a validated questionnaire.

RESULTS

Thirty-one subjects completed the study; 17 were randomized to ranitidine. The pretreatment median aggregate dyspepsia score of the placebo group was 0 (0-4), as was that of the ranitidine group (0-8) (N.S.). During the 10 days after completion of ranitidine, the median aggregate dyspepsia score was 1.4 (0-30), compared with 0 (0-6.3) after placebo (p < 0.01). Of those given ranitidine, 59% experienced dyspepsia after treatment, compared with only 14% who took placebo. In the subgroup that developed dyspepsia after active therapy, the median duration of symptoms was 2 days, symptom severity being maximal on the second day after completion of the tablets. On the days when dyspepsia was experienced, the median daily dyspepsia score was 5 (range, 2-10), which was similar to that of a control group with active duodenal ulcer disease (5; range, 0-11).

CONCLUSIONS

Withdrawal of a 2-month course of ranitidine 300 mg nocte results in the development of dyspeptic symptoms in a proportion of previously asymptomatic subjects. Patients receiving ranitidine should be warned about this rebound dyspepsia and advised not to immediately resume treatment, as rebound symptoms are likely to improve within a few days.

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.

Protective effects of oleanolic acid oligoglycosides on ethanol- or indomethacin-induced gastric mucosal lesions in rats

We examined the effects of various oleanolic acid oligoglycosides obtained from traditional herbs on ethanol- or indomethacin-induced gastric mucosal lesions in rats and on gastric secretion in pylorus-ligated rats. Test samples were given orally to fasted rats 1 h before absolute ethanol (1.5 ml/rat, p.o.) or indomethacin (30 mg/kg, s.c.) treatment, or ligation of the pylorus. Oleanolic acid 3-O-monodesmosides [oleanolic acid 3-O-glucuronide (1, 20-50 mg/kg), momordin Ic (2, 5-50 mg/kg), and 28-O-deglucosyl-chikusetsusaponins IV (5, 10-50 mg/kg) and V (7, 10-50 mg/kg)] were found to show protective effects on ethanol-induced gastric mucosal lesions, whereas oleanolic acid 3,28-O-bisdesmosides [momordin IIc (3), chikusetsusaponins IV (4) and V (6)], oleanolic acid 28-O-monodesmoside [compound O (8)], and their common aglycon [oleanolic acid (9)] showed no such effects. Oleanolic acid 3-O-monodesmosides (1, 2, and 5) also showed protective effects on indomethacin-induced gastric mucosal lesions. 28-O-Deglucosyl-chikusetsusaponin V (7) did not inhibit the indomethacin-induced lesions, while chikusetsusaponins V (6, 50 mg/kg) had the gastroprotective effect. These active saponins (1, 2, 4-7, 10-50 mg/kg) did not decrease the gastric secretion by oral administration in pylorus-ligated rats.

Role of gastric acid in the aetiology of dyspeptic disease and dyspepsia

The main diseases associated with dyspepsia are peptic ulcer disease, gastro-oesophageal reflux disease and non-ulcer dyspepsia. Increased gastric acid secretion is a characteristic of most duodenal ulcer patients and of a small minority of non-ulcer dyspepsia and gastro-oesophageal reflux disease patients. Although acid secretion is normal in most gastro-oesophageal reflux disease patients, the condition is mainly the result of excess exposure of the distal oesophagus to acid refluxing from the stomach. Increased mucosal sensitivity to acid is involved in the aetiology of dyspeptic symptoms in the majority of patients with peptic ulcer disease and gastro-oesophageal reflux disease, and in a minority of non-ulcer dyspepsia subjects. Gastric acid, therefore, plays an important role in both the aetiology of dyspeptic diseases and in the aetiology of dyspeptic symptoms.

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.

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.

Optimizing acid suppression for treatment of acid-related diseases

Gastric acid is of central importance in the pathogenesis of duodenal ulcer, gastric ulcer, and gastroesophageal reflux disease. Pharmacological reduction of acid secretion is, therefore, the mainstay of current treatment, but the optimal degree of acid suppression remains incompletely understood. This paper considers the ideal ways of assessing and reporting the pharmacological effectiveness of acid-inhibiting drugs and relating such data to clinical efficacy. Twenty-four-hour intragastric pH measurements are widely used for this purpose, although this technique cannot measure secretion quantitatively. Data on suppression of 24-hr intragastric acidity for groups of subjects have been successfully correlated with healing rates for duodenal ulcer, gastric ulcer, and gastroesophageal reflux disease. Three primary determinants of healing have been derived from antisecretory data. These are the degree of suppression of acidity, the duration of suppression of acidity, and the duration of treatment. The order of importance of these determinants varies depending on the disease. Data on 24-hr intragastric acidity should be accompanied whenever possible by data on 24-hr plasma gastrin levels, as the relationship between suppression of acidity and a rise in gastrin varies widely between individuals. It is not possible to predict the plasma gastrin level from the intragastric pH or any other measurement of intragastric acidity. Comparative data sets in groups of subjects may provide useful information. Proton pump inhibitors produce a greater and longer-lasting degree of suppression of acidity than conventional doses of H2-receptor antagonists. For this reason, they are more effective in healing duodenal ulcer and gastric ulcer. However, in view of the importance of duration of treatment, healing rates with the H2-receptor antagonists approach those obtained with proton pump inhibitors if treatment is continued for a longer time. In gastroesophageal reflux disease in particular, although the optimal degree of acid suppression is not yet defined, the consistently superior performance of proton pump inhibitors demonstrates that increased suppression of acidity is clinically beneficial.

Influence of initial therapy on outcome of peptic ulcer

Histamine 2 (H2) receptor antagonists, proton pump inhibitors, prostaglandin analogues, colloidal bismuth and sucralfate have all proved safe and effective in the initial treatment of peptic ulcer. Yet, most ulcers will recur when treatment is stopped. Continuous maintenance with H2 antagonists results in low symptomatic relapse, complications occur rarely, and such treatment is safe. An alternative is Symptomatic Self Care (on-demand therapy), which provides an economic option for patients with no concomitant disease or previous complications. Meta-analyses suggest a higher relapse rate after H2 antagonist therapy than that following sucralfate or bismuth. Whilst improved morphology and/or functional status of the gastro-duodenal mucosa ('quality of healing') has been claimed, the difference has not been explained. Successful prolonged eradication of Helicobacter pylori leads to a very low relapse rate, but more effective, predictable and safer eradication regimens are needed.

Acid inhibitory characteristics of nizatidine in man: an overview

The antisecretory activity of nizatidine, an H2-receptor antagonist, has been extensively investigated in man both by quantitative acid secretory tests and by means of 24-h continuous ambulatory pH monitoring. Studies have shown that nizatidine is a potent inhibitor of basal, nocturnal and stimulated acid secretion. Particular modalities of nizatidine administration, such as early evening intake with supper or morning dosing, have been recently defined. Further studies are needed to clarify if rebound nocturnal acid hypersecretion may develop after abrupt withdrawal of nizatidine or if tolerance may develop during prolonged administration.

A proposition for the diagnosis and treatment of gastro-oesophageal reflux disease in children: a report from a working group on gastro-oesophageal reflux disease. Working Group of the European Society of Paediatric Gastro-enterology and Nutrition (ESPGAN)

In this paper, a Working Group on Gastro-Oesophageal Reflux discusses recommendations for the first line diagnostic and therapeutic approach of gastro-oesophageal reflux disease in infants and children. All members of the Working Group agreed that infants with uncomplicated gastro-oesophageal reflux can be safely treated before performing (expensive and often unnecessary) complementary investigations. However, the latter are mandatory if symptoms persist despite appropriate treatment. Oesophageal pH monitoring of long duration (18-24 h) is recommended as the investigation technique of choice in infants and children with atypical presentations of gastro-oesophageal reflux. Upper gastro-intestinal endoscopy in a specialised centre is the technique of choice in infants and children presenting with symptoms suggestive of peptic oesophagitis. Prokinetics, still a relatively new drug family, have already obtained a definitive place in the treatment of gastro-oesophageal reflux disease in infants and children, especially if "non-drug" treatment (positional therapy, dietary recommendations, etc.) was unsuccessful. It was the aim of the Working Group to help the paediatrician with this consensus statement and guide-lines to establish a standardised management of gastro-oesophageal reflux disease in infants and children.

Quality of healing in peptic ulcer disease--are H2 receptor antagonists all we need?

The rapid relief of symptoms and ulcer healing can now be achieved in most patients with peptic ulcer. Histamine2 (H2) receptor antagonists, proton pump inhibitors, prostaglandin analogues, colloidal bismuth and sucralfate have all proved safe and effective for the initial treatment of peptic ulcer. However, most ulcers will recur when treatment is stopped. Meta-analyses suggest a higher relapse rate after H2 antagonist therapy than that following sucralfate or bismuth. This difference has not been explained although improved morphology and/or functional status of the gastroduodenal mucosa ("quality of healing") has been claimed. Eradication of Helicobacter pylori leads to marked reduction in relapse rate but more effective and safer eradication regimens are needed. Since most ulcers do recur, maintenance therapy with H2 antagonists remains a commonly used option. Continuous maintenance results in low symptomatic relapse, complications occur rarely, and such treatment is safe. An alternative is Symptomatic Self Care (on-demand therapy) which provides an economic option for patients with no concomitant disease or previous complications. Future research should decide the exact role of Helicobacter eradication; but for now, we can still rely on maintenance therapy with the widely-used and proven H2 receptor antagonists.

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.

Changes in nocturnal and peak acid outputs after duodenal ulcer healing with sucralfate or ranitidine

Changes in basal and stimulated acid secretion after duodenal ulcer healing have been previously shown to be influenced by the nature of the treatment. This study aimed to determine possible changes in nocturnal acid secretion on duodenal ulcer healing in patients treated with sucralfate or ranitidine. Nocturnal acid output and peak acid output in response to pentagastrin stimulation were studied in 20 patients before and after duodenal ulcer healing with sucralfate (n = 9) or ranitidine (n = 11). Details regarding cigarette smoking were obtained from each subject. Median 10 hour nocturnal acid output fell significantly (p less than 0.05) from 82.4 (29.1-188.3) mmol (median range) to 45.2 (14.7-144.4) mmol after healing with sucralfate, and rose significantly (p less than 0.05) from 54.7 (16.8-74.3) mmol to 86.2 (11.7-118.1) mmol after ulcer healing with ranitidine. Peak acid output fell from 39.6 (22.0-52.8) mmol/hour to 27.8 (13.8-38.2) mmol/hour (p less than 0.01) after healing with sucralfate and was unchanged after healing with ranitidine. There was no correlation between smoking and nocturnal acid output. These results provide further evidence that acid secretion decreases with sucralfate healing and remains the same or may even increase after ranitidine healing.

The H2-receptor antagonist era in duodenal ulcer disease

This paper reviews the remarkable impact of H2-receptor antagonists on duodenal ulcer management. The development and the scientific rationale of these agents are presented, and efficacy and safety aspects in the short- and long-term treatment of duodenal ulcer disease discussed. Attention is focused on the possible role of "acid rebound" in ulcer relapse following the withdrawal of therapy and on the clinical relevance of prolonged suppression of acid secretion in patients on long-term therapy.

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.

Tolerance and rebound to H2-receptor antagonists: intragastric acidity in patients with duodenal ulcer

Tolerance to the antisecretory effects of H2-receptor antagonists develops consistently in healthy volunteers. The aim of this study was to determine whether tolerance occurs with repeated dosing of H2-receptor antagonists in patients with duodenal ulcer. Continuous intragastric 24-hr pH measurements were performed in 12 patients with duodenal ulcer in symptomatic remission before, on days 1 and 29, and two days after receiving ranitidine 300 mg four times a day for 34 days. The 24-hr median intragastric pH (interquartile range) was 5.4 (4.4-6.1) on day 1 and 4.6 (4.0-5.2) on day 29 of dosing with ranitidine (not significant). Median nighttime pH was 6.8 (6.3-7.0) on day 1 and 6.8 (6.6-7.1) on day 29 (not significant). During the daytime, the median pH decreased marginally from 4.7 (3.8-5.2) on day 1 to 3.8 (3.0-4.6) on day 29 (P less than 0.03). There was no difference in median intragastric pH during 24-hr, day and night periods before and two days after ranitidine dosing. No significant tolerance or rebound to H2-receptor antagonists was observed in patients with duodenal ulcer disease. This contrasts with data gathered in healthy volunteers and may be due to defects in the regulation of acid secretion in duodenal ulcer disease.

Treatment of peptic ulcer disease with sucralfate: a review

Sucralfate has been used widely for the treatment of peptic ulcer. Healing rates for duodenal ulcer range from 60 to 90% at 4-6 weeks and up to 90% at 12 weeks for gastric ulcer. The small number of maintenance trials suggest that relapse of duodenal ulcer is reduced comparably to H2 receptor antagonists. There has been considerable interest in the possibility of lower relapse ratios after initial healing with sucralfate compared with H2 receptor antagonists, but more studies of the possible mechanisms as well as larger trials are still needed to confirm these observations.

Acid secretory responses and parietal cell sensitivity following duodenal ulcer healing with omeprazole, sucralfate, and Maalox

Acid secretory responses and parietal cell sensitivity (PCS) have been studied in 21 duodenal ulcer patients before and after successful treatment with omeprazole (n = 7), sucralfate (n = 7), or Maalox (n = 7). The second study was carried out 3 days after documented healing and withdrawal of treatment in the sucralfate- and Maalox-treated groups and 14 days after documented healing and withdrawal of treatment in the omeprazole-treated patients. Acid output (mmol/hour) was measured as basal secretion, and in response to 0.1 microgram/kg/hour pentagastrin (low-dose) and 6.0 micrograms/kg/hour pentagastrin (high-dose) stimulation. PCS was calculated as the ratio of low dose:high dose acid output (expressed as a percentage). Ulcer healing with sucralfate resulted in significant (p less than 0.05) decreases in low-dose acid output from 36.4% (13.2-51.0) (median [range]) to 8.4% (3.2-45.4) mmol/hour and PCS from 69.1% (44.9-91.4) to 22.0% (16.0-85.6), whereas no significant decreases in any of the measured parameters were noted following ulcer healing with Maalox. Ulcer healing with omeprazole resulted in significant (p less than 0.05) decreases in basal acid output from 6.3 (1.5-22.9) (median [range]) to 2.2 (0-6.9) mmol/hour, and low-dose acid output from 31.0 (6.0-58.0) to 23.0 (1.4-44.8) mmol/hour. These findings suggest that acid secretory responses following ulcer healing vary according to the therapeutic agent used.