Inhibition Of Acid Secretion Research Articles

Soraprazan: Setting New Standards in Inhibition of Gastric Acid Secretion

After treatment of millions of patients suffering from gastroesophageal reflux disease (GERD) and other acid-related ailments with proton pump inhibitors, there are still unmet medical needs such as rapid and reliable pain relief, especially for nocturnal acid breakthrough. In this work, we introduce and characterize the biochemistry and pharmacology of the potassium-competitive acid blocker (P-CAB) soraprazan, a novel, reversible, and fast-acting inhibitor of gastric H,K-ATPase. Inhibitory and binding properties of soraprazan were analyzed together with its mode of action, its selectivity, and its in vivo potency. This P-CAB has an IC(50) of 0.1 microM if measured with ion leaky vesicles and of 0.19 microM in isolated gastric glands. With a K(i) of 6.4 nM, a K(d) of 26.4 nM, and a B(max) of 2.89 nmol/mg, this compound is a highly potent and reversible inhibitor of the H,K-ATPase. Soraprazan shows immediate inhibition of acid secretion in various in vitro models and in vivo and was found to be more than 2000-fold selective for H,K-ATPase over Na,K- and Ca-ATPases. Soraprazan is superior to esomeprazole in terms of onset of action and the extent and duration of pH elevation in vivo in the dog. Rapid and consistent inhibition of acid secretion by soraprazan renders the P-CABs a promising group of compounds for therapy of GERD.

Are gastroprotective drugs useful for gastric ulcer healing: Re-evaluation using current ICH E9 guidelines

Most of the gastroprotective drugs which had been marketed in Japan were considered to have insufficient rationale for use as ulcer treatments. Such drugs may have a crucial role in maintaining mucosal integrity by the mechanisms other than inhibition of acid secretion. We re-evaluated the effect of gastroprotective drugs on gastric ulcer healing using current ICH E9 guidelines. We collected reports of pivotal trials on healing rate of gastric ulcer with 9 kinds of gastroprotective drugs submitted in New Drug Applications. In the comparative trial of cetraxate vs. placebo, the healing rate of gastric ulcer at 8-week endoscopy in the cetraxate was significantly higher than that in the placebo groups (88.6% and 62.2%, p = 0.0062). Non-inferiority to cetraxate was confirmed for 8 kinds of gastroprotective drugs. In conclusion, the superiority of cetraxate over placebo and non-inferiority to cetraxate for 7 drugs was established in the respect of effect on ulcer healing.

Inhibition of Neutrophil Activation by Lafutidine, an H2-receptor Antagonist, Through Enhancement of Sensory Neuron Activation Contributes to the Reduction of Stress-Induced Gastric Mucosal Injury in Rats

Sensory neuron activation reduces water-immersion restraint stress (WIR)-induced gastric mucosal injury by inhibiting neutrophil activation through increase in endothelial production of prostacyclin. This study was designed to examine whether lafutidine, which is an H(2)-receptor antagonist and activates sensory neurons, inhibits neutrophil activation, thereby reducing WIR-induced gastric mucosal injury. Lafutidine enhanced WIR-induced increases in gastric tissue levels of calcitonin gene-related peptide (CGRP) and 6-keto-PGF(1alpha), a stable metabolite of prostacyclin, whereas famotidine, another H(2)-receptor antagonist, did not. Such lafutidine-induced increases in gastric tissue levels of 6-keto-PGF(1alpha) were reversed by pretreatment with capsazepine, an inhibitor of sensory neuron activation, CGRP(8-37), a CGRP antagonist, and indomethacin. Lafutidine inhibited acid-induced exacerbation of gastric mucosal injury in animals subjected to WIR by inhibiting neutrophil activation, whereas famotidine did not. Lafutidine synergistically increased CGRP release from isolated rat dorsal root ganglion neurons in the presence of anandamide, but famotidine did not. These observations suggest that lafutidine might reduce WIR-induced gastric mucosal injury not only by inhibiting acid secretion but also by inhibiting neutrophil activation through enhancement of sensory neuron activation.

Dyspepsia and Helicobacter pylori

#### Practical tips Dyspepsia is common; up to 40% of adults in the United Kingdom have the condition. A general practitioner will see on average 210 patients with dyspepsia each...

Therapeutic Approaches Towards the Treatment of Gastrointestinal Disorders

The Society for Medicines Research gathered an international panel of speakers and about 60 delegates for their symposium September 21, 2006, on Therapeutic Approaches Towards the Treatment of Gastroinstestinal Disorders, at the National Heart and Lung Institute, in London, U.K. The focus of the conference was to discuss therapeutic strategies taken towards the treatment of inflammatory bowel disease, acid related disorders and irritable bowel syndrome. Key note lectures addressed the development of tegaserod, a 5-HT(4) receptor agonist, for the treatment of constipation dominant irritable bowel syndrome (cIBS), the use of tumor necrosis factor alpha (TNFalpha) inhibitors in the treatment of chronic inflammatory diseases, including Crohn's disease, the development of effective inhibitors of gastric acid secretion, the role of alpha(4)beta(7) integrin in the development of Crohn's disease and ulcerative colitis, the parts played by the neuropeptides ghrelin and motilin in the control of gastrointestinal motility, and the role of bacteria in functional gastrointestinal disease.

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.

Corticosteroid therapy in Henoch-Schönlein gastritis

Henoch-Schönlein purpura (HSP) is the most common vascular disease of childhood. It is a multisystem disease most commonly affecting the skin,joints, gastrointestinal tract, and kidneys, but other organs may be affected, too. Gastrointestinal involvement occurs in approximately 65-90% of patients, ranging from mild symptoms such as abdominal pain, nausea, and vomiting, to more severe manifestations such as gastrointestinal bleeding and intussusception. In most cases, HSP spontaneously resolves without treatment. The use of corticosteroids is controversial and usually reserved for severe systemic manifestations. Some authors suggest that the abdominal pain and gastrointestinal hemorrhage of HSP may respond to steroids, with some suggesting that there is a benefit in their use and describing a regimen. This is a case report of HSP in a fourteen-year-old boy with abdominal pain and hematemesis. Upper endoscopy showed an edematous and erythematous change in the body of the stomach and purpuric lesions in the duodenum, while multiple erosions were found in the antral area. Parenteral corticosteroid therapy with gastric acid secretion inhibitor administration led to regression of gastrointestinal symptoms on the seventh day, with relapses on the fourth and sixth day. Peroral administration of corticosteroids and gradual decrease of daily doses started on the eighth day of abdominal symptoms. New purpuric skin rashes appeared during six weeks. Corticosteroid therapy with gastric acid secretion inhibitors showed a positive effect in our patient with a severe form of HSP accompanied by abdominal pain and gastrointestinal hemorrhage.

Diets and Circadian Rhythms: Challenges from Biology for Medicine

Autoimmune diseases such as rheumatoid arthritis and gastrointestinal disorders such as stomach ulcers are often treated with drugs. NSAIDs, a common treatment in rheumatoid arthritis, may cause stomach ulcers which call for additional medications, notably antacids in the sense of drugs that suppress acid secretion by the stomach. Infection with Helicobacter pylori also plays a role in the ulcers. The infection is typically treated with antibiotics added to antacids. Considering NSAIDs and antacids, we suspect that overmedication is common to the extent that particular diets are a better option. Current research and current treatments with these drugs are also problematic since circadian rhythms are mostly disregarded. All the processes involved in the disorders treated show marked variations in the course of the day. Hence experiments conforming to the guidelines of evidence-based medicine, and treatments in line with them, have outcomes strongly depending on the time factor. This calls for reforms in medicine with fresh inputs from biology.

Molecular pharmacological approach to drug actions on the afferent and efferent fibres of the vagal nerve involved in gastric mucosal protection in rats

Gastric mucosal protection is associated with the actions of anti-ulcer drugs or agents affecting on the afferent and/or efferent nerve fibres of the vagal nerve. 1. To identify the dose-response curves of drugs (compounds) on the afferent vanilloid-receptor (capsaicin or resiniferatoxin-sensitive) and on efferent secretion (atropine, pirenzepine, cimetidine, ranitidine, famotidine, omeprazole, esomeprazole) basal gastric acid and stimulated gastric secretion in relation to the chemically-induced gastric mucosal damage in rats; 2. To determine the ED50 (pD2) and pA2 on the calculation of affinity and intrinsic affinity curves for these agonists/antagonists, as an indication of relative potency of effects. The observations were carried out in rats (30 different models). The ED50 values for affinities of capsaicin, resiniferatoxin were obtained in nmol/kg b.w. range, whereas the values were in the nmol/kg to micromol/kg b.w. ranges for effects on the gastric basal, stimulated (bethanechol, pentagastrin, histamine) gastric secretion, and the gastric mucosal damage-produced by different ulcerogenic agents (ethanol, HCl, aspirin, indomethacin). From the observations, that agents acting on vanilloid (capsaicin) receptors were the most potent inhibitors of acid secretion and gastric lesions from necrotizing agents, suggests that the capsaicin sensitive afferent nerves have a primary place in the efferent regulated events leading to initiation of gastric mucosal damage.

Validation of a New Endoscopic Technique to Assess Acid Output in Zollinger–Ellison Syndrome

To safely manage the hypersecretory state in patients with Zollinger-Ellison syndrome, both upper endoscopy and gastric analysis are required to titrate optimal medical therapy. Conventional gastric analysis requires more than 1 hour to perform and results in significant patient dissatisfaction. In this study, we have validated endoscopic gastric analysis as a novel technique that can effectively replace conventional gastric analysis. In a prospective, cross-over study, 12 patients with Zollinger-Ellison syndrome underwent gastric analysis, first by the conventional method and then by an endoscopic technique performed on the same day. Acid concentration was determined by titration, volume output was recorded, and acid output was calculated using standard methodologies and formulas. Agreement was assessed following the Bland-Altman method. To assess repeatability, both techniques were repeated on the same day in a subset of patients. Excellent agreement was reported between acid output (95% limits of agreement, -1.27 to 1.61 mEq/h) and acid concentration (95% limits of agreement, -0.01 to 0.01 mEq/mL), although poor agreement was observed between volume output measured. Endoscopic gastric analysis showed greater reproducibility regarding acid and volume output measured. We introduce a new, rapid, reproducible, and accurate endoscopic technique to measure acid output in patients with Zollinger-Ellison syndrome who require both annual endoscopy and gastric analysis. The data presented here suggest that endoscopic gastric analysis would be equally effective in determining acid output in other hypersecretory states. Additional analysis of cost effectiveness is needed to evaluate its use as a screening tool in select populations.

Inhibition of the gastric H +,K +-ATPase by plectrinone A, a diterpenoid isolated from Plectranthusbarbatus Andrews

This work assessed the mechanism underlying the antisecretory gastric acid effect of Plectranthus barbatus Andrews (Lamiaceae) and active constituents. Popularly known as “false-boldo”, this plant is used in Brazilian folk medicine to treat gastrointestinal and hepatic ailments. The plant aqueous extract (AE) and isolated compounds were assayed in vivo in pylorus-ligated mice, and in vitro on acid secretion measured as [ 14C]-aminopyrine ([ 14C]-AP) accumulation in rabbit gastric glands and gastric H +,K +-ATPase preparations. Injected into the duodenal lumen, the AE of the plant leaves (0.5 and 1.0 g/kg) decreased the volume (62 and 76%) and total acidity (23 and 50%) of gastric acid secretion in pylorus-ligated mice. Bioguided purification of the AE yielded an active fraction (IC 50 = 24 μg/ml) that inhibited acid secretion in rabbit gastric glands with a potency 10 to 18 times greater than that of the originating extract, on both the basal and stimulated acid secretion by histamine (His) (1 μM) or bethanechol (100 μM). At the same concentrations the gastric H +,K +-ATPase activity was also inhibited. The active constituent was chemically identified as the abietanoid dienedione plectrinone A which reduced the H +,K +-ATPase activity with IC 50 = 171 μM. The results indicate that inhibition of the gastric proton pump by this diterpenoid may account for the antisecretory acid effect and reputed antiulcer activity of Plectranthus barbatus.

Treatment of gastroesophageal reflux disease

To review the literature on the treatment of gastroesophageal reflux disease (GERD) with emphasis on pharmacological aspects. To identify particularities of pharmacological treatment of esophageal and extraesophageal manifestations of the disease. Electronic search of the PubMed/MEDLINE and Cochrane Collaboration databases. Controlled and randomized studies published since 2000 and reviews representing consensus positions and directives published within the last 10 years were identified. The drugs currently available for the treatment of GERD do not act in the primary mechanism of the disease, i.e. transitory relaxation of the lower esophageal sphincter. Pharmacological treatment of GERD with symptoms or with esophageal injury is based on the suppression of acid secretion, particularly with proton pump inhibitors. When the hyperreactivity of the lower airways coexists with esophageal GERD symptoms, suppression of acid secretions should be of benefit in managing the respiratory disease in the presence of a causal relationship; however, this is not usual. When esophageal symptoms are not present, esophageal 24-hour pH study should be carried out prior to starting pharmacological treatment for GERD. Improvement of respiratory symptoms may be delayed with relation to esophageal symptoms. It is common for GERD to recur and pharmacological treatment should be repeated or continued indefinitely, depending on clinical presentation of the disease. The strategies that have been proposed for the pharmacological treatment of GERD in children are primarily based on studies of case series or on studies with adults. There have been very few controlled and randomized studies in children. Undertaking a greater number of these studies might reinforce existing aspects or establish new aspects of management.

Tratamento da doença do refluxo gastroesofágico

OBJETIVO: Rever a literatura sobre tratamento da doença do refluxo gastroesofágico (DRGE) com ênfase nos aspectos farmacológicos. Identificar particularidades do tratamento farmacológico nas manifestações esofágicas e extra-esofágicas da doença. FONTES DE DADOS: Busca eletrônica na base de dados PubMed/MEDLINE e Cochrane Collaboration. Procurou-se identificar estudos controlados e randomizados publicados a partir de 2000, bem como revisões que representassem consensos e diretrizes publicados nos últimos 10 anos. SÍNTESE DOS DADOS: Nenhuma das drogas atualmente usadas no tratamento da DRGE altera comprovadamente o mecanismo principal da doença, ou seja, os relaxamentos transitórios do esfíncter esofágico inferior. O tratamento farmacológico da DRGE com sintomas ou com lesões esofágicas é baseado na inibição da secreção ácida, em particular pelos inibidores da bomba de prótons (IBP). Nas situações em que a hiper-reatividade das vias aéreas inferiores coexiste com sintomas esofágicos da DRGE, a inibição da secreção ácida deve trazer benefícios na condução da doença respiratória se houver uma relação causal; contudo, essa situação não é comum. Quando não coexistem sintomas esofágicos, a pHmetria esofágica de 24 h deve ser realizada previamente ao tratamento farmacológico da DRGE. A melhora dos sintomas respiratórios pode ser tardia em relação aos sintomas esofágicos. A DRGE freqüentemente recorre, e o tratamento farmacológico deve ser repetido ou mantido indefinidamente, conforme a apresentação clínica da doença. CONCLUSÃO: As condutas propostas para o tratamento farmacológico da DRGE na criança são oriundas principalmente de estudos de séries de casos ou de estudos em adultos. Existem poucos estudos controlados e randomizados em crianças. A realização de um número maior desses estudos poderá reafirmar ou introduzir novos aspectos nas condutas propostas.

Molecular mechanisms involved in anti-inflammatory effects of proton pump inhibitors

Interleukin (IL)-8 has been reported to participate in neutrophil infiltration in Helicobacter pylori (H. pylori)-induced gastritis in humans. In this study, we investigated the anti-inflammatory actions beyond the suppression of acid secretion by proton pump inhibitors (PPI), such as omeprazole and lansoprazole, on IL-8 production by gastric epithelial cells (MKN45) and human umbilical vein endothelial cells (HUVEC) and on the transendothelial migration of polymorphonuclear neutrophils (PMN). MKN45 and HUVEC were stimulated with H. pylori water extract (HPE) and IL-1beta, respectively, and nuclear factor kappa B (NFkappaB) activation and subsequent IL-8 production was assessed in the absence or presence of PPI. We also assessed the effect of PPI on IL-8-induced PMN transendothelial migration and on the alteration of cytoplasmic calcium concentration in formyl-methionyl-leucyl-phenylalanine (fMLP)-stimulated PMN. HPE and IL-1beta induced a significant increase in IL-8 production by MKN45 and HUVEC, respectively, along with NFkappaB activation, which was significantly inhibited by PPI. PPI also inhibited the IL-8-induced transendothelial migration of PMN and the fMLP-induced cytosolic calcium increase in PMN. PPI attenuate PMN-dependent gastric mucosal inflammation partly by interfering with NFkappaB activation in vascular endothelial cells and gastric epithelial cells, and partly by modulating the calcium concentration of PMN.

Implementation of an Algorithm for Intravenous Pantoprazole: Impact on Prescription Compliance in Quebec University Hospitals

Background: Intravenous pantoprazole is used at Centre Hospitalier de l'Université de Montréal (CHUM) for the adjuvant treatment of nonvariceal upper gastrointestinal bleeding (UGB) and for inhibiting acid secretion among patients unable to tolerate oral intake (NPO). Since it was added to the CHUM formulary, the use of intravenous pantoprazole has steadily increased, and at times it has been used without endoscopic documentation of a nonvariceal UGB or even when the patient could have received a proton pump inhibitor orally. Objective: To assess the impact of an algorithm for intravenous pantoprazole on prescription compliance. Methods: Using a pre–post intervention specification, the use of pantoprazole was audited on a retrospective (January 1, 2002, to April 30, 2002) and prospective (January 1, 2003, to April 30, 2003) basis. We reviewed the medical records of all patients having received intravenous pantoprazole during these periods, assessing the compliance of prescriptions as specified by the algorithm. Cost of therapy and the step-down regimen were also reviewed. Results: In total, 150 patients were identified in the retrospective phase and 109patients in the prospective phase. The subjects were organized into 2 groups: UGB and NPO. In the UGB group, rates of compliance with indication, dose, and duration of treatment in the retrospective phase were 8.8%, 76.5%, and 58.8%, respectively; the corresponding rates for the prospective phase were 26.5% (p < 0.01), 80.9% (p = 0.53), and 69.1% (p = 0.78), respectively. The total rates of compliance (including indication, dose, and duration) were 4.4% in the retrospective phase and 11.8% in the prospective phase (p = 0.12). In the NPO group, the rate of compliance at the initiation of pantoprazole was 42.7% in the retrospective phase and 36.6% in the prospective phase (p = 0.51). The cost of noncompliance with the indication in the UGB group was estimated at $12 270 CDN (in the retrospective phase) and $7829 (in the prospective phase). In the NPO group, the cost figures were $8048 (retrospective phase) and $5929 (prospective phase). Conclusions: This study demonstrates that intravenous pantoprazole is being used in a suboptimal manner in our institution. Despite explicit criteria for use, in the prospective phase, we observed only 11.8% total compliance in the UGB group and 36.6% compliance at the initiation of pantoprazole in the NPO group. Even though these results were not statistically significant, in the prospective phase, we saw improvement in most compliance rates.

A Mannose-Binding Lectin-Defective Haplotype Is a Risk Factor for Gastric Cancer

El-Omar et al. (1) reported that interleukin (IL)-1 gene cluster variants that enhance the production of IL-1β (a powerful inhibitor of gastric acid secretion) increase the risk of gastric cancer in Helicobacter pylori (HP)-infected patients. IL-1β production is down-regulated by mannose-binding lectin (MBL) (2), an acute-phase glycoprotein that has a high affinity for gram-negative lipopolysaccharide and exerts immunological activity (3)(4). Variants in the promoter, the 5′UTR, and exon 1 of the MBL2 gene reduce the synthesis and activity of MBL (5). To assess the relationships between MBL2 gene variants and HP-related gastric cancer, we analyzed the whole coding region and the 5′UTR of the MBL2 gene in DNA extracted (QIAamp, Qiagen) from neoplastic cells embedded in paraffin sections (used for histological diagnosis) from 145 unrelated patients (90 males) affected by noncardia gastric cancer. Eighty-seven (60.0%) had intestinal-type; 47 (32.4%), diffuse-type; and 11 (7.6%), mixed-type adenocarcinoma. All patients had HP-positive serology. For 75 patients, we …

Roles of Protease-Activated Receptor-2 (PAR-2), a G Protein-Coupled Receptor, in Modulation of Exocrine Gland Functions

Protease-activated receptor-2 (PAR-2), a G protein-coupled receptor, is activated by proteolytic unmasking of the N-terminal extracellular tethered ligand that presumably binds to the extracellular loop 2 of the receptor itself. PAR-2 is widely distributed in the mammalian body and plays various roles in biological events in the cardiovascular, respiratory, alimentary, and central neurons systems. PAR-2-activating peptides administered systemically to mice and rats trigger prompt salivation in vivo. In an in vitro study, PAR-2 agonists including the endogenous PAR-2 activator trypsin induce secretion of amylase and mucin from isolated rat parotid glands and sublingual glands, respectively. PAR-2-activating peptides administered systemically also modulate pancreatic exocrine secretion in vivo as well as in vitro. In the gastric mucosa, PAR-2 stimulation enhances secretion of mucus and pepsinogen and suppresses acid secretion. Tear secretion can also be caused by PAR-2-related peptides in PAR-2-dependent and -independent manners. PAR-2 thus plays a general or key role in the regulation of exocrine secretion. This review focuses on the physiologic and/or pathophysiologic roles of PAR-2 in glandular exocrine secretion. The possibility of PAR-2 as a target for drug development is also discussed.

Advantages and disadvantages of lumping together gastroesophageal reflux disease and dyspepsia

The aim of this article is to identify and to balance the arguments in favor of and against lumping together gastroesophageal reflux disease and functional dyspepsia. In at least half of the patients diagnosed with gastroesophageal reflux disease no organic abnormalities are found. Hypersensitivity of the esophagus to various stimuli plays a key role in the genesis of symptoms in these patients. The association between symptoms and acid reflux events can be quantified by 24-h esophageal pH monitoring. It has also become possible to detect non-acid reflux, using the intraluminal impedance monitoring technique. Functional dyspepsia is still defined by a combination of symptoms for which no organic cause can be found. No positive diagnostic tools have yet become available and treatment with acid secretion inhibitors, Helicobacter pylori eradication or prokinetic drugs remains marginally effective. Gastroesophageal reflux disease is a well defined disease which can be diagnosed objectively with endoscopy or 24-h pH/impedance monitoring with symptom association analysis. Functional dyspepsia is a functional disorder for which no objective test has yet been discovered. Treatment of gastroesophageal reflux disease is based on objectively identified abnormalities and highly effective. Treatment of functional dyspepsia is empiric and marginally effective. For these reasons, the lumping together of gastroesophageal reflux disease and functional dyspepsia is not to be advised.

Clinical impact of CYP2C19 polymorphism on the action of proton pump inhibitors: a review of a special problem

Proton pump inhibitors (e.g. omeprazole/esomeprazole, lansoprazole, pantoprazole, rabeprazole) have a prominent role in the short- and long-term management of acid-related intestinal disease. They are eliminated by the hepatic route and the polymorphic CYP2C19 is involved in their metabolism. Three phenotypes have been identified in various populations: extensive metabolizers (homEM), poor metabolizers (PM) and individuals carrying one wild type and one mutant allele (hetEM). Therefore, systemic drug exposure (AUC) varies widely between these three populations and the AUC for omeprazole, lansoprazole and rabeprazole are approximately 7.5-, 4.5- and 4-fold higher in PM than in homEM. Since the pharmacodynamic response to proton pump inhibitors (PPIs) is related to their AUC, intragastric pH is much more elevated in PM (median around 6) and hetEM (4 - 5) than in homEM (3 - 4). This genotype-dependent increase in AUC and intragastric pH has clinical consequences because the healing rate in peptic ulcer (PU, target pH > or = 3) and gastroesophageal reflux disease (GERD, target pH > or = 4) and the eradication of Helicobacter pylori (Hp) depend on a long-lasting (> or = 16 hours) and effective inhibition of acid secretion. Several clinical studies have shown that PM and hetEM benefit from an approximately 18% higher Hp eradication rate compared to homEM when standard dosages of PPIs are administered orally. In our own study with lansoprazole (+ amoxicillin, clarithromycin, metronidazole) the eradication rates were 100, 98 and 80% in PM, hetEM and homEM, respectively, and in patients with GERD treated with lansoprazole (30 mg/day) the healing rates after 8 weeks were much higher in PM (85 - 100%) and hetEM (68 - 95%) than in homEM (46 - 77%). In a further study with esomeprazole (40 mg/day) in 205 patients with GERD we were surprised to observe that the healing rate after 4 weeks was not dependent on the CYP2C19 genotype. In an accompanying pharmacokinetic trial in 10 patients with GERD, both esomeprazole and 5-OH-esomeprazole (formed by CYP2C19) plasma levels and those of omeprazole-sulfone (formed by CYP3A4) were determined. Based on the calculated metabolic ratios it could be shown that CYP3A4 plays a major role in kinetics of esomeprozale, particularly after multiple dosing when there is a metabolic shift in favor of the formation of the sulfone. In conclusion, for most PPIs the activity of CYP2C 19 determines the level of drug exposure (AUC), pharmacodynamic response (elevation of intragastric pH and serum levels of gastrin) and clinical outcome (Hp eradication, healing rates of PU and GERD). Thus, a genotype-adjusted dosage regimen will improve therapeutic efficacy of PPIs.

Characteristics of the K+-competitive H+,K+-ATPase inhibitor AZD0865 in isolated rat gastric glands

The gastric H+,K+-ATPase of the parietal cell is responsible for acid secretion in the stomach and is the main target in the pharmacological treatment of acid-related diseases. Omeprazole and other benzimidazole drugs, although having delayed efficacy if taken orally, have high success rates in the treatment of peptic ulcer disease. Potassium competitive acid blockers (P-CAB) compete with K+ for binding to the H+,K+-ATPase and thereby they inhibit acid secretion. In this study, the in vitro properties of AZD0865, a reversible H+,K+-ATPase inhibitor of gastric acid secretion, are described. We used a digital-imaging system and the pH sensitive dye BCECF to observe proton efflux from hand-dissected rat gastric glands. Glands were stimulated with histamine (100 microM) and exposed to a bicarbonate- and Na+-free perfusate to induce an acid load. H+,K+-ATPase inhibition was determined by calculating pHi recovery (dpH/dT) in the presence of omeprazole (10-200 microM) or AZD0865 (0.01-100 microM). The efficacies of both drugs were compared. Our data show that acid secretion is inhibited by both the proton pump inhibitor omeprazole and the P-CAB AZD0865. Complete inhibition of acid secretion by AZD0865 had a rapid onset of activation, was reversible, and occurred at a 100-fold lower dose than omeprazole (1 microM AZD0865 vs. 100 microM omeprazole). This study demonstrates that AZD0865 is a potent, fast-acting inhibitor of gastric acid secretion, effective at lower concentrations than drugs of the benzimidazole class. Therefore, these data strongly suggest that AZD0865 has great potential as a fast-acting, low-dose inhibitor of acid secretion.