Review article: the clinical pharmacology of proton pump inhibitors

Comparison of the efficacy and safety of pantoprazole magnesium and pantoprazole sodium in the treatment of gastro-oesophageal reflux disease: a randomized, double-blind, controlled, multicentre trial

BACKGROUND

Proton pump inhibitors (PPIs) are well established as first-line agents for the treatment of moderate-to-severe gastro-oesophageal reflux disease (GORD). Although all PPIs heal oesophageal lesions and provide symptomatic relief, breakthrough symptoms may occur as acidity levels rebound. Pantoprazole magnesium (pantoprazole-Mg) has a longer elimination half-life than pantoprazole sodium (pantoprazole-Na), resulting in prolonged drug exposure.

OBJECTIVE

This study compares the clinical efficacy and safety of once-daily pantoprazole-Mg 40 mg with that of once-daily pantoprazole-Na 40 mg in the management of GORD.

METHODS

This was a randomized, double-blind, controlled, multicentre study of non-inferiority design in outpatients with GORD. The study was conducted in 53 centres in Germany from 12 May 2003 to 18 September 2003. Male or female outpatients (aged ≥18 years) with endoscopically confirmed GORD stage I-III (according to the Savary-Miller classification modified by Siewert) were enrolled. Using a computer-generated randomization list, patients were randomized to treatment with pantoprazole-Mg 40 mg plus placebo or pantoprazole-Na 40 mg plus placebo, both given once daily for 4 or 8 weeks depending on healing of oesophagitis. The primary objective was endoscopic healing at 8 weeks.

RESULTS

The intent-to-treat (ITT) group consisted of 636 patients (322 receiving pantoprazole-Mg and 314 receiving pantoprazole-Na). Endoscopically confirmed healing of reflux oesophagitis after 8 weeks occurred in 87.3% (95% CI 83.1, 90.7) of patients receiving pantoprazole-Mg and 85.0% (95% CI 80.6, 88.8) of patients receiving pantoprazole-Na (ITT population). The lower bound of the 95% CI for the between-group treatment difference was -1.3, which was within the predefined margin of non-inferiority of -10% to 0%. Healing rates after 4 weeks were superior in the pantoprazole-Mg group (72.7% [95% CI 67.5, 77.5]) compared with the pantoprazole-Na group (66.2% [95% CI 60.7, 71.5]), and the one-sided (lower bound) of the 95% CI for the difference between healing rates for the two treatments was within the predefined non-inferiority margin of -10% to 0%. Both treatments had a similar effect on GORD healing in subgroups of patients based on baseline oesophagitis grade and Helicobacter pylori status. Pantoprazole-Mg had similar efficacy to pantoprazole-Na in relieving a broad range of GORD-related symptoms across the course of the study, although symptomatic relief at 4 weeks was numerically higher in the pantoprazole-Mg group than in the pantoprazole-Na group (statistical analyses were not performed). Both treatments were well tolerated; most adverse events were of mild or moderate severity and unrelated to the study medication, and there were no unexpected safety concerns.

CONCLUSION

Pantoprazole-Mg is clinically as effective and well tolerated as pantoprazole-Na in the treatment of GORD stages I-III, demonstrating non-inferiority for oesophageal healing at 8 weeks and superior healing rates at 4 weeks associated with high levels of symptomatic relief.

Long-term acid inhibition: benefits and harms

Proton pump inhibitors (PPIs) are the drugs of choice in the therapy of acid-related disorders. PPIs are as a class remarkably safe. Serious adverse events such as acute interstitial nephritis are extremely rare. Some reports in recent years have placed some concern on the long-term use of PPIs. Long-term therapy with PPIs can cause hypochlorhydria, hypergastrinemia and has interactions on hepatic cytochrome P450 enzymes which might increase the risk of infectious complications, nutritional deficiencies and drug-drug interactions. The vast majority of data came from retrospective case-control or cohort studies which are prone to confounders. At the moment we cannot conclude that long-term PPI use causes anemia, osteoporosis and bone fractures, increases the risk for pulmonary or enteric infections, has an effect on GUT mucosa, polyp or tumor formation, or that PPI use increases the risk of cardiovascular events in patients on PPIs and clopidogrel. We need prospective randomized trials to be able to definitely answer the questions raised in epidemiologic studies. Maintenance therapy with PPIs should be started only if strict indications for that therapy are fulfilled.

New pharmacologic approaches in gastroesophageal reflux disease

This article highlights current and emerging pharmacological treatments for gastroesophageal reflux disease (GERD), opportunities for improving medical treatment, the extent to which improvements may be achieved with current therapy, and where new therapies may be required. These issues are discussed in the context of current thinking on the pathogenesis of GERD and its various manifestations and on the pharmacologic basis of current treatments.

Ilaprazole, a new proton pump inhibitor, is primarily metabolized to ilaprazole sulfone by CYP3A4 and 3A5

Ilaprazole is a new proton pump inhibitor, designed for treatment of gastric ulcers, and developed by Il-Yang Pharmaceutical Co (Seoul, Korea). It is extensively metabolised to the major metabolite ilaprazole sulfone. In the present study, several in vitro approaches were used to identify the cytochrome P450 (CYP) enzymes responsible for ilaprazole sulfone formation. Concentrations of ilaprazole sulfone were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Incubation of ilaprazole with cDNA-expressed recombinant CYPs indicated that CYP3A was the major enzyme that catalyses ilaprozole to ilaprazole sulfone. This reaction was inhibited significantly by ketoconazole, a CYP3A inhibitor, and azamulin, a mechanism-based inhibitor of CYP3A, while no substantial effect was observed using selective inhibitors for eight other P450s (CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP2E1). In addition, the formation of ilaprazole sulfone correlated well with CYP3A-catalysed testosterone 6β-hydroxylation and midazolam 1'-hydroxylation in 20 different human liver microsome panels. The intrinsic clearance of the formation of ilaprazole sulfone by CYP3A4 was 16-fold higher than that by CYP3A5. Collectively, these results indicate that the formation of the major metabolite of ilaprazole, ilaprazole sulfone, is predominantly catalysed by CYP3A4/5.

Dexlansoprazole MR: a review

Dexlansoprazole MR is the R-enantiomer of lansoprazole that is delivered by a novel system, the dual delayed release formulation. The drug has been shown to be efficacious in healing erosive esophagitis as compared with lansoprazole. When compared to placebo, dexlansoprazole provided significantly higher maintenance rates for healed esophageal mucosa in patients with erosive esophagitis and symptom control in patients with non-erosive reflux disease. Dexlansoprazole could be taken without regard to food. Overall, dexlansoprazole is well tolerated and has a comparable side-effect profile to lansoprazole.

Proton pump inhibitor-associated pneumonia: Not a breath of fresh air after all?

Over the past two decades, proton pump inhibitors (PPIs) have emerged as highly effective and relatively safe agents for the treatment of a variety of gastrointestinal disorders. Unfortunately, this desirable pharmacological profile has also contributed to superfluous and widespread use in both the inpatient and outpatient settings. While generally well-tolerated, research published over the last decade has associated these agents with increased risks of Clostridium difficile disease, fractures likely due to calcium malabsorption and both community-acquired (CAP) and hospital-acquired pneumonias (HAP). The mechanism behind PPI-associated pneumonia may be multifactorial, but is thought to stem from compromising the stomach’s “acid mantle” against gastric colonization of acid-labile pathogenic bacteria which then may be aspirated. A secondary postulate is that PPIs, through their inhibition of extra-gastric H⁺/K⁺-ATPase enzymes, may reduce the acidity of the upper aerodigestive tract, thus resulting in increased bacterial colonization of the larynx, esophagus and lungs. To date, several retrospective case control studies have been published looking at the association between PPI use and CAP. Some studies found a temporal relationship between PPI exposure and the incidence of pneumonia, but only two could define a dose-response relationship. Furthermore, other studies found an inverse correlation between duration of PPI use and risk of CAP. In terms of HAP, we reviewed two retrospective cohort studies and one prospective study. One retrospective study in a medical ICU found no increased association of HAP in PPI-exposed patients compared to no acid-lowering therapy, while the other in cardiothoracic surgery patients showed a markedly increased risk compared to those receiving H₂RAs. The one prospective study in ICU patients showed an increased risk of HAP with PPIs, but not with H₂RAs. In conclusion, the current literature shows a slight trend toward an association between PPI use and pneumonia and an increased risk with PPIs over H₂RAs, but the findings are not consistent across all studies. Larger controlled trials still need to be done to better identify the risk that PPIs impart towards patients contracting CAP or HAP. Until these are completed, we will have to continue to extrapolate across smaller controlled trials to predict the associated risks in our respective patient populations. In the interim, it appears prudent to limit the use of PPIs to situations where they are clinically indicated and, in such cases, use them at the lowest effective dose. In the case of prescribing for stress ulcer prophylaxis in ICU patients, perhaps H₂RAs should be used as the preferred agents over PPIs.

The resurgence of covalent drugs

Covalent drugs have proved to be successful therapies for various indications, but largely owing to safety concerns, they are rarely considered when initiating a target-directed drug discovery project. There is a need to reassess this important class of drugs, and to reconcile the discordance between the historic success of covalent drugs and the reluctance of most drug discovery teams to include them in their armamentarium. This review surveys the prevalence and pharmacological advantages of covalent drugs, discusses how potential risks and challenges may be addressed through innovative design, and presents the broad opportunities provided by targeted covalent inhibitors.

Intragastric acidity during administration of generic omeprazole or esomeprazole - a randomised, two-way crossover study including CYP2C19 genotyping

BACKGROUND

Generic omeprazole has been approved in many countries for the treatment of acid-related gastrointestinal disorders. However, clinical studies comparing generic to original proton pump inhibitors are limited.

AIMS

To compare the effect of generic omeprazole 20 mg/day with esomeprazole 20 mg/day on intragastric acidity and to investigate the influence of the CYP2C19 metabolizer status.

METHODS

In this randomised, single-blinded, two-way crossover study, 24 healthy Helicobacter pylori-negative subjects, received generic omeprazole (Omep; Hexal AG, Holzkirchen, Germany) 20 mg once daily or esomeprazole 20 mg once daily for five consecutive days. Twenty-four-hour intragastric pH was recorded on day 5 of each treatment. CYP2C19 status was determined by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

Over all, there were no statistically significant differences between generic omeprazole and esomeprazole with respect to median intragastric pH (3.5 and 3.9, P = 0.07), the total hours with intragastric pH >4 (10.4 and 11.3, P = 0.29), and during upright (9.6 and 9.1, P = 0.77) or supine (2.2 and 2.2, P = 0.94) position. However, in CYP2C19 rapid metabolizers, esomeprazole was superior to omeprazole, with the percentage of time with intragastric pH >3.0 and pH >3.5 being higher with esomeprazole than with generic omeprazole [Δ = 9% (P = 0.026) and Δ = 8% (P = 0.046), respectively].

CONCLUSIONS

Overall, generic omeprazole 20 mg appears to provide a similar intragastric acid control when compared with esomeprazole 20 mg. However, esomeprazole might be advantageous in subjects with a rapid CYP2C19 metabolizer status.

Appropriateness of treatment recommendations for PPI in hospital discharge letters

PURPOSE

The reasons for the dramatic increase in proton pump inhibitors (PPI) prescriptions remain unclear and cannot be explained solely by increased morbidity, new indications or a decrease in alternative medication. Inappropriate use and discharge recommendations in hospitals are considered to be possible explanations. As the quality of PPI recommendations in hospital discharge letters in Germany has not been investigated to date, we have studied the appropriateness of these referrals.

METHODS

Hospital discharge letters with recommendations for PPI medication from 35 primary care practices in the county of Mecklenburg-Western Pomerania (MV; North-east Germany) were collected and analysed, and the appropriateness of the PPI indication was rated.

RESULTS

No information justifying the recommendation for continuous PPI medication could be identified in 54.5% of the discharge letters; in 12.7%, the indication was uncertain, and in 32.7%, we found an evidence-based indication for PPI medication. The most common indication for adequate PPI use was nonsteroidal anti-inflammatory drug-prophylaxis in high-risk patients.

CONCLUSIONS

Inadequate recommendations for PPIs in discharge letters are frequent. This may lead to a continuation of this therapy in primary care, thereby unnecessarily increasing polypharmacy and the risk of adverse events as well as burdening the public health budget. Hospitals should therefore critically review recommendations for PPI medication and the dosage thereof in their discharge letters and clearly document the reason for PPI use and the need for continuous prescription in primary care.

Relative bioavailability and pharmacokinetic properties of two different enteric formulations of esomeprazole in healthy Bangladeshi male volunteers: An open-label, single-dose, randomized-sequence, two-way crossover study

BACKGROUND

In Bangladesh, a number of generic oral formulations of esomeprazole are marketed. Study of the relative bioavailability of these generic formulations has yet to be conducted in a Bangladeshi population.

OBJECTIVES

The aims of this study were to assess the relative bioavailability and pharmacokinetic properties of 2 formulations (test and reference) of esomeprazole 40 mg.

METHODS

This open-label, randomized, 2-way crossover study was conducted in healthy Bangladeshi male subjects in compliance with the Declaration of Helsinki and International Conference on Harmonisation guidelines. Subjects were randomly assigned to receive the test formulation followed by the reference formulation or vice versa, as a single dose of esomeprazole 40 mg after a 12-hour overnight fast. A washout period of 1 week was maintained between treatments. Following oral administration, blood samples were collected at 0, 0.5, 0.75, 1, 1.25, 1.5, 1.75, 2, 2.25, 2.5, 2.75, 3, 3.5, 4, 5, 7, 9, and 12 hour(s) after dosing and analyzed for esomeprazole concentrations using a validated HPLC method. Pharmacokinetic parameters, including C(max), AUC(0-12), and AUC(0-infinity), were determined with a non-compartmental method. The formulations were to be considered bioequivalent if the natural log (ln)-transformed ratios of the pharmacokinetic parameters were within the predetermined bioequivalence range of 80% to 125%, according to the US Food and Drug Administration (FDA) requirement. The within- and between-group differences were examined using ANOVA. Tolerability was assessed by monitoring vital signs and conducting subject interviews regarding adverse events. Interviewers were not blinded to study design.

RESULTS

A total of 24 nonsmoking, healthy, Bangladeshi male subjects (mean [SD] age, 22.8 [2.22] years [range, 20-29 years]; weight, 64.7 [6.9] kg [range, 55-79 kg]; height, 1.69 [0.05] m [range, 1.63-1.82 m]; and body mass index, 22.39 [2.16] kg/m(2) [range, 18.99-27.34 kg/m(2)]) were enrolled. From serum data, the mean (SD) values for the test and reference products were as follows: 5.26 (1.57) and 5.54 (2.94) micromol/L for C(max); 2.53 (0.67) and 2.07 (0.65) hours for T(max); 15.74 (6.50) and 16.68 (6.77) micromol/L/h for AUC(0-12); and 17.15 (7.58) and 18.26 (7.31) micromol/L/h for AUC(0-infinity), respectively. The mean T(max) was found to be significantly different between the test and reference formulations (2.53 [0.67] vs 2.07 [0.65] hours, respectively; P < 0.05). The point estimates (90% CI) for the test/reference ratios of the In-transformed AUC(0-infinity) and C(max) were 92.92% (84.02%-102.76%) and 102.36% (85.96%-121.90%), respectively, which were within the FDA-accepted limits for assuming bioequivalence. No adverse events were reported by the volunteers during the study.

CONCLUSION

This single-dose study found that the test and reference formulations of esomeprazole 40 mg met the FDA regulatory criteria for assuming bioequivalence in these healthy, fasting Bangladeshi male volunteers. A significant difference was found in T(max) between the 2 formulations. Both formulations were well tolerated in the studied population.

Interaction between clopidogrel and proton-pump inhibitors and management strategies in patients with cardiovascular diseases

Dual antiplatelet therapy (DAPT) with clopidogrel and aspirin has been successful in reducing ischemic events in a wide range of patients with cardiovascular diseases. However, the anti-ischemic effects of DAPT may also be associated with gastrointestinal (GI) complications including ulceration and bleeding particularly in ‘high risk’ and elderly patients. Current guidelines recommend the use of proton-pump inhibitors (PPIs) to reduce the risk of GI bleeding in patients treated with DAPT. However, pharmacodynamic studies suggest an effect of PPIs on clopidogrel metabolism with a resultant reduction in platelet inhibitory effects. Similarly, several observational studies have demonstrated reduced clopidogrel benefit in patients who coadministered PPIs. Although recent US Food and Drug Administration and European Medicines Agency statements discourage PPI (particularly omeprazole) and clopidogrel coadministration, the 2009 AHA/ACC/SCAI PCI guidelines do not support a change in current practice in the absence of adequately powered prospective randomized clinical trial data. The data regarding pharmacologic and clinical interactions between PPI and clopidogrel therapies are herein examined and treatment strategies are provided.

Safety of proton pump inhibitor exposure

Proton pump (H(+)/K(+)-adenosine triphosphatase) inhibitors (PPIs) are widely used to treat patients with acid-related disorders because they are generally perceived to be safe and effective. However, as with any pharmacologic agent, they have the potential for side effects. Many studies have examined the side effects of long-term or short-term PPI exposure. We review the mechanism of action of PPIs, focusing on recently released products that might have greater risks of adverse effects than older products because of increased potency and/or duration of action. We summarize the data available on the putative adverse effects of PPI therapy and propose guidelines for clinicians who prescribe these agents to limit the potential for adverse outcomes in users of these effective therapeutic agents.

Inhibiting gastric acid production does not affect intestinal calcium absorption in young, healthy individuals: a randomized, crossover, controlled clinical trial

Proton pump inhibitors (PPIs) are the most potent gastric acid suppressing drugs available, and their use is widespread. An emerging concern about chronic PPI therapy is whether these drugs impair intestinal calcium absorption, resulting in a negative calcium balance and thereby potentially causing bone loss. The objective of this study was to evaluate the acute effect of the PPI esomeprazole or placebo on intestinal calcium absorption in healthy adults. Twelve young adults participated in a placebo-controlled, double-blind, crossover study. There were two 3-week interventions that included a 14-day adjustment period (designed to stabilize calcium homeostasis) followed by 6 days of a diet containing 800 mg of calcium and 2.1 g/kg of protein (intervention). During the last 3 days of the adjustment period and throughout the intervention period, subjects consumed esomeprazole or placebo. Half the subjects underwent 24-hour continuous gastric acid pH monitoring. Intestinal calcium absorption was measured using dual-stable calcium isotopes at the end of each intervention. Treatment with esomprazole significantly increased gastric pH (mean pH on PPI 5.38 +/- 0.13, mean pH on placebo 2.70 +/- 0.44, p = .005). Neither calcium absorption (PPI 34.2% +/- 2.4%, placebo 31.5% +/- 2.1%, p = .24) nor urinary calcium (PPI 321 +/- 38 mg/34 hours, placebo 355 +/- 37 mg/34 hours, p = .07) differed between the PPI and placebo groups. It is concluded that short-term gastric acid suppression by PPIs does not attenuate intestinal calcium absorption in healthy young adults.

A randomized controlled trial comparing two different dosages of infusional pantoprazole in peptic ulcer bleeding

AIM

The optimal dosage of proton pump inhibitor in bleeding peptic ulcers remains controversial. The aim was to compare the clinical effectiveness of two doses of infusional pantoprazole in peptic ulcer bleeding.

METHODS

Peptic ulcer patients (n= 120) with bleeding stigmata were enrolled after successful endoscopic therapy. After an initial bolus injection of 80 mg pantoprazole, patients were randomized to receive continuously infused pantoprazole at either 192 mg day(-1) or 40 mg every 6 h (i.e. 160 mg day(-1)) for 3 days. Clinical outcomes between the two groups within 14 days were compared, with 14-day recurrent bleeding regarded as the primary end-point.

RESULTS

Both groups (n= 60 each) were well matched in demographic and clinical factors upon entry. Bleeding totally recurred in 11 (9.2%) patients, with six (10%) in the 192 mg day(-1) group and five (8.3%) in the 160 mg day(-1) group (relative risk of bleeding recurrence between two treatments 1.2; 95% CI 0.39, 3.72). All secondary outcomes between the two groups were similar, including the amount of blood transfusion (mean 1179 ml vs. 1203 ml, P > 0.1), hospital stay (mean 9.5 days vs. 9.9 days, P > 0.1), need for surgery (n= 1 vs. n= 0, P > 0.1), and mortality (n= 1 vs. n= 0, P > 0.1).

CONCLUSIONS

Following endoscopic haemostasis, infusional pantoprazole at either 192 mg day(-1) or 40 mg every 6 h appear similar.

New pharmacologic approaches in gastroesophageal reflux disease

This article highlights current and emerging pharmacological treatments for gastroesophageal reflux disease (GERD), opportunities for improving medical treatment, the extent to which improvements may be achieved with current therapy, and where new therapies may be required. These issues are discussed in the context of current thinking on the pathogenesis of GERD and its various manifestations and on the pharmacologic basis of current treatments.

E3710, a new proton pump inhibitor, with a long-lasting inhibitory effect on gastric acid secretion

We have investigated the pharmacology of sodium (R)-2-[4-(2,2-dimethyl-1,3-dioxan-5-yl) methoxy-3,5-dimethylpyridin-2-yl]methylsulfinyl-1H-benzimidazol (E3710), a new proton pump inhibitor (PPI), and its effect on gastric acid secretion. E3710 irreversibly inhibited H(+),K(+)-ATPase activity in pig gastric vesicles with an acidic internal environment with an IC(50) of 0.28 microM. Administration of E3710 (0.1, 0.2, 0.4, and 0.8 mg/kg; n = 6) intraduodenally in a gastric fistula model in dogs inhibited histamine-stimulated gastric acid secretion at 0 to 2 and 24 to 26 h after administration with ED(50) values of 0.18 and 0.22 mg/kg, respectively. The inhibition by E3710 was 2.3 times more potent than that of another representative PPI, esomeprazole (0.2, 0.4, 0.8, and 1.6 mg/kg; n = 6) at 0 to 2 h after administration (ED(50) = 0.40 mg/kg) and 2.8 times more potent at 24 to 26 h (ED(50) = 0.71 mg/kg). In the gastric fistula dogs, the intragastric pH was >or=4 for 17% (n = 27) of a 24-h period with vehicle alone, but when E3710 was administered, at 0.2 (n = 4), 0.4 (n = 8), and 0.8 mg/kg (n = 5), the pH was >or=4 for 40, 79, and 88% of a day, respectively. The corresponding values for esomeprazole at 0.8 (n = 4) and 1.6 mg/kg (n = 8) were 55 and 59%, respectively. In a crossover study with vehicle, E3710 at 0.4 mg/kg and esomeprazole at 1.6 mg/kg (n = 6), E3710 increased the intragastric pH to >4 for 82% of a day compared with 61% of a day with esomeprazole. These results show that E3710 is a long-acting inhibitor of gastric acid secretion and a promising novel therapy for acid-related diseases, such as gastroesophageal reflux disease.

The pharmacodynamics and pharmacokinetics of S-tenatoprazole-Na 30 mg, 60 mg and 90 mg vs. esomeprazole 40 mg in healthy male subjects

BACKGROUND

Racemic tenatoprazole 40 mg/day provides more prolonged acid suppression than esomeprazole 40 mg/day.

AIM

To compare pharmacodynamic and pharmacokinetic profiles of tenatoprazole and esomeprazole.

METHODS

A single-centre, double-blind, double-dummy, randomized, 4-way, cross-over study was conducted in 32 healthy male subjects. S-tenatoprazole-Na 30, 60 or 90 mg, or esomeprazole 40 mg was administered once daily for 5 days with 10-day washout intervals. The 24-h intragastric pH was recorded at baseline and on day 5 of each period.

RESULTS

On day 5, median pH (5.34 +/- 0.45 and 5.19 +/- 0.52 vs. 4.76 +/- 0.82, respectively, P < 0.002) and percentage time with pH > 4 (80 +/- 11 and 77 +/- 12, vs. 63 +/- 11 respectively, P < 0.0001) for 24-h were higher with S-tenatoprazole-Na 90 mg and 60 mg than esomeprazole. In nocturnal periods, S-tenatoprazole-Na 90 mg, 60 mg and 30 mg were superior to esomeprazole with regard to median pH (5.14 +/- 0.64, 4.94 +/- 0.65, 4.65 +/- 0.86 and 3.69 +/- 1.18 respectively, P < 0.0001) and percentage time with pH > 4 (77 +/- 12, 73 +/- 17, 64 +/- 17 and 46 +/- 17 respectively, P < 0.0001). Proportion of subjects with nocturnal acid breakthrough with S-tenatoprazole-Na 90 mg, 60 mg and 30 mg was significantly less than with esomeprazole (54.8, 43.3, 56.7 and 90.3 respectively, P < 0.04). The proportion of subjects with >16 hrs with pH >4 was significantly higher with S-tenatoprazole-Na 90 mg and 60 mg than with esomeprazole (87.1%, 83.3% and 41.9% respectively, P < 0.02).

CONCLUSIONS

S-tenatoprazole-Na produced significantly greater and more prolonged dose-dependent 24-h and nocturnal acid suppression than esomeprazole. S-tenatoprazole-Na may provide greater clinical efficacy compared with current PPIs for patients with ineffective once-daily therapy.

CYP2C19 genotypes in the pharmacokinetics/pharmacodynamics of proton pump inhibitor-based therapy of Helicobacter pylori infection

IMPORTANCE OF THE FIELD

Proton pump inhibitors (PPIs) are potent gastric acid inhibitors. Therapies with a PPI and antibiotics are used to cure Helicobacter pylori (H. pylori) infection, which is closely related to many gastrointestinal diseases. Most PPIs are mainly metabolized by cytochrome 2C19 (CYP2C19). The genetic polymorphisms of CYP2C19 may lead to the differences in pharmacokinetics (PK), pharmacodynamics (PD) and clinical efficacy of PPIs.

AREAS COVERED IN THIS REVIEW

The roles of PPIs on the eradication of H. pylori are summarized. The impact f CYP2C19 polymorphism on the PK and PD of PPIs is addressed and related to the present status of therapy for H. pylori infection. The opinions on the strategy of PPIs-based therapies of H. pylori infection are provided.

WHAT THE READER WILL GAIN

Update the factors that may influence the PPIs-based therapies of H. pylori infection.

TAKE HOME MESSAGE

The eradication rates of H. pylori infection are significantly different between patients who are CYP2C19 extensive metabolizers and poor metabolizers, partly because of the differences in the PK and PD of PPIs. Nonetheless, the differences can be improved by adjusting the regimens of PPIs and using antibiotics that have less H. pylori-resistance.

Proton pump inhibitor lansoprazole is a nuclear liver X receptor agonist

The liver X receptors (LXRalpha and LXRbeta) are transcription factors that control the expression of genes primarily involved in cholesterol metabolism. In the brain, in addition to normal neuronal function, cholesterol metabolism is important for APP proteolytic cleavage, secretase activities, Abeta aggregation and clearance. Particularly significant in this respect is LXR mediated transcriptional control of APOE, which is the only proven risk factor for late onset Alzheimer's disease. Using a transactivation reporter assay for screening pharmacologically active compounds and off patent drugs we identified the proton pump inhibitor Lansoprazole as an LXR agonist. In secondary screens and counter-screening assays, it was confirmed that Lansoprazole directly activates LXR, increases the expression of LXR target genes in brain-derived human cell lines, and increases Abca1 and Apo-E protein levels in primary astrocytes derived from wild type but not LXRalpha/beta double knockout mice. Other PPIs activate LXR as well, but the efficiency of activation depends on their structural similarities to Lansoprazole. The identification of a widely used drug with LXR agonist-like activity opens the possibility for systematic preclinical testing in at least two diseases--Alzheimer's disease and atherosclerosis.

Revisiting the parietal cell

The parietal cell is responsible for secreting concentrated hydrochloric acid into the gastric lumen. To fulfill this task, it is equipped with a broad variety of functionally coupled apical and basolateral ion transport proteins. The concerted scientific effort over the last years by a variety of researchers has provided us with the molecular identity of many of these transport mechanisms, thereby contributing to the clarification of persistent controversies in the field. This article will briefly review the current model of parietal cell physiology and ion transport in particular and will update the existing models of apical and basolateral transport in the parietal cell.

Preventing the gastrointestinal adverse effects of nonsteroidal anti-inflammatory drugs: from risk factor identification to risk factor intervention

Nonsteroidal anti-inflammatory drugs (NSAIDs) have huge prescription volumes, for two main reasons: the aging of the population is increasing the prevalence of diseases that respond to NSAIDs, such as osteoarthritis; and NSAIDs are highly effective drugs that contribute crucially to the management of many diseases. In France, the number of physician orders that include an NSAID is estimated at 25 to 30 million per year. Nevertheless, the use of NSAIDs is limited by adverse effects. The gastrointestinal tract is the main target of NSAID toxicity, and NSAID therapy is among the leading causes of bleeding from upper gastrointestinal ulcers. Adverse events targeting the lower gastrointestinal tract are also of concern, although they receive less attention. To effectively prevent NSAID toxicity, it must be recognized that the risk of adverse events can be diminished but not eliminated. Therefore, the risk/benefit ratio must be carefully evaluated at each prescription. A number of risk factors should be emphasized. Thus, the risk increases with age, and there is a sharp risk increase at 60 years of age. Other risk factors include a history of ulcers (most notably with bleeding), the use of high NSAID dosages, Helicobacter pylori infection, and the concomitant use of antiplatelet agents. Minimizing NSAID-related gastrointestinal toxicity requires a careful risk factor evaluation; selection of the most appropriate NSAID and NSAID dosage; and, in some patients, prophylactic gastroprotective therapy, for instance with a proton pump inhibitor. Gastrointestinal symptoms either have no value for predicting gastrointestinal events or occur too late to serve as alarm signals. The toxicity advantages of cyclooxygenase-2 inhibitors seem modest and do not eliminate the need for this rational prescription strategy.

The pharmacology of esomeprazole and its role in gastric acid related diseases

Esomeprazole (S-isomer of omeprazole) demonstrates a better pharmacokinetic/pharmacodynamic profile than the racemic product omeprazole. Esomeprazole's pharmacological activity of gastric acid secretion is through proton pump inhibition. The pharmacokinetic properties provide for an enhanced pharmacological effect. Esomeprazole is rapidly absorbed and the extent of absorption is higher resulting in higher systemic absorption of esomeprazole (bioavailability), which coupled with reduced clearance results in greater systemic exposure. This pharmacodynamic profile then provides for a prolongation of inhibition of gastric acid output and correlates well with its more beneficial therapeutic efficacy over omeprazole and some of the other proton-pump inhibitors. It has been well proven as an effective agent in the treatment of gastro-esophagitis reflux disease, (reflux esophagitis and non-erosive reflux disease), NSAID-induced gastric-intestinal symptoms and ulcers, Helicobacter pylori infection and Zollinger-Ellison syndrome. Esomeprazole has a good tolerability profile and a low potential for drug interaction.

A single dose of intravenous esomeprazole decreases gastric secretion in healthy volunteers

BACKGROUND

Data suggest that esomeprazole decreases gastric secretion.

AIMS

To assess the effect of a single i.v. esomeprazole dose on gastric secretion volume 3 h after drug administration, as a primary endpoint, and to evaluate, as secondary endpoints, the reduction 1 and 5 h after dosing; time when the gastric pH was <2.5 and esomeprazole's safety.

METHODS

In all, 23 healthy Helicobacter pylori-negative volunteers (10 men, 13 women, mean age 28.2 +/- 6) participated in this single-centre, randomized, double-blind, placebo-controlled, 2-way, single-dose cross-over study. In different sessions, volunteers received i.v. either esomeprazole 40 mg or placebo. An inserted double-lumen nasogastric tube perfused and aspirated gastric liquid. Mechanical fractioned aspiration measured secretion volume; aliquot spectrophotometry assessed gastric secretion volume lost to the duodenum.

RESULTS

Three hours post-i.v. esomeprazole, average gastric secretion decreased by 77.6% (vs. baseline) compared to placebo. Values 1 and 5 h after dosing were 73.5% and 74.5%. Five hours after esomeprazole, the gastric pH was <2.5 3.9% of the time and 73.3% after placebo (P < 0.002). Esomeprazole was well-tolerated. No serious adverse events occurred.

CONCLUSIONS

Intravenous esomeprazole decreases gastric secretions. The potential clinical impact in averting bronchoaspiration during anaesthesia induction and in intensive care patients should be investigated in further studies.

[Gastro-esophageal reflux through gastric antisecretory drugs]

During the 20th century, gastro-esophageal reflux moved from the status of a rare and severe disease to that of a frequent disease occurring mostly, in the absence of any significant lesions. Proton pump inhibitors (PPIs) are the mainstay of its therapy and are prescribed mainly in an empirical way. Extradigestive manifestations require more accurate diagnostic tests and therapeutic management. The modalities of prescription of the PPIs quickly progressed toward the on-demand therapy and over-the-counter PPIs should become widespread. The relative failures of PPIs led to a profusion of new antisecretory agents but clinical improvements are presently disappointing and the rationale of this escalation is questionable. The concept of non acid gastro-esophageal reflux opens more innovative diagnostic and therapeutic perspectives which, however, must be validated. In this respect, endoscopic treatment needs more reliable techniques and more rigorous trials. Gastro-esophageal reflux refractory to PPIs corresponds mainly to functional esophageal disorders that need diagnostic and therapeutic improvements. Barrett's esophagus constitutes a major challenge for the next few years. Its screening and its prevention seem, for the moment, inaccessible. Its survey and the prevention of its complications should benefit from progress of diagnostic and interventional endoscopy.

Characterization of mechanisms underlying the effects of esomeprazole on the impairment of gastric ulcer healing with addition of NSAID treatment

BACKGROUND

The efficacy of proton pump inhibitors in patients at high risk of gastrointestinal injury receiving non-steroidal anti-inflammatory drugs is currently debated.

AIMS

To evaluate the effects of esomeprazole on the impairment of gastric ulcer healing associated with non-steroidal anti-inflammatory drug treatment.

METHODS

Gastric ulcers were induced in rats by acetic acid. Four days later, animals were treated daily with equivalent acid-inhibiting doses of esomeprazole or famotidine, alone or in combination with indomethacin. At day 3 or 7 of treatment, ulcerated tissues were processed to assess: ulcer area; malondialdehyde; prostaglandin E(2); nuclear factor-kB; proliferating cell nuclear antigen and caspase-3 (Western blot).

RESULTS

In indomethacin-treated animals, esomeprazole was more effective than famotidine or the antioxidant melatonin in promoting ulcer healing. Malondialdehyde levels were increased by indomethacin, and this effect was counteracted by esomeprazole, but not famotidine. Esomeprazole and famotidine, given alone or in combination with indomethacin, increased proliferating cell nuclear antigen expression. Increased levels of prostaglandin E(2) were detected in ulcerated tissues. Ulcer prostaglandin E(2) production was reduced by indomethacin, alone or in combination with esomeprazole or famotidine, while it was enhanced when esomeprazole or famotidine were tested alone. The activation of caspase-3 was induced by indomethacin, and this effect was prevented by esomeprazole, but not famotidine. In the presence of indomethacin, esomeprazole, but not famotidine, enhanced nuclear factor-kB activation in gastric ulcers.

CONCLUSIONS

Esomeprazole counteracts the detrimental action of indomethacin on ulcer repair through both acid-dependent and acid-independent effects. The acid-independent actions are related to decrease in tissue oxidation and apoptosis and to enhancement of nuclear factor-kB activation.

Review article: dual delayed release formulation of dexlansoprazole MR, a novel approach to overcome the limitations of conventional single release proton pump inhibitor therapy

BACKGROUND

Proton pump inhibitors (PPIs) provide the most effective pharmacotherapy for treating acid-related disorders. However, PPIs do not completely control acid over 24 h with once-daily dosing.

AIMS

To discuss limitations inherent in the pharmacokinetics (PK) and pharmacodynamics of conventional PPI formulations, which provide a single drug release. Also, to consider approaches to extending the duration of acid suppression focusing on dexlansoprazole MR, a PPI with a novel Dual Delayed Release (DDR) formulation.

METHOD

We reviewed the available literature regarding marketed and investigational PPIs.

RESULTS

Non-standard dosing of currently marketed PPIs has produced incremental advances in acid control. Multiple approaches are being evaluated to enhance acid suppression with PPIs. Dexlansoprazole MR is a DDR formulation of dexlansoprazole, an enantiomer of lansoprazole, with two distinct drug release periods to prolong the plasma dexlansoprazole concentration-time profile and extend duration of acid suppression. Clinical studies show that dexlansoprazole MR produces a dual-peak PK profile that maintains therapeutic plasma drug concentrations longer than lansoprazole, with a single-peak PK profile, and increases the percentage of time that intragastric pH >4.

CONCLUSIONS

Novel drug delivery platforms, including the dexlansoprazole MR DDR formulation, may improve acid suppression and offer benefits over conventional single release PPI formulations.

Proton pump inhibitors: actions and reactions

Proton pump inhibitors are the second most commonly prescribed drug class in the United States. The increased utilization of PPIs parallels the rising incidence of reflux disease. Owing to their clinical efficacy and relative lack of tachyphylaxis, PPIs have largely displaced H-2 receptor antagonists in the treatment of acid peptic disorders. The elevation of intragastric pH and subsequent alterations of gastric physiology induced by PPIs may yield undesired effects within the upper GI tract. The ubiquity of the various types of H(+), K(+)-ATPase could also contribute to non-gastric effects. PPIs may influence physiology in other ways, such as inducing transepithelial leak.

Controversies in the treatment of gastroesophageal reflux disease in preterm infants

Gastroesophageal reflux (GER) is common in preterm infants and usually is a physiologic phenomenon with little clinical consequence. GER resulting in clinical signs and symptoms is considered pathologic gastroesophageal reflux disease (GERD). Correlation of clinical signs and symptoms with GER has been poor in most studies. The efficacy of GERD therapy has not been studied systematically in preterm infants. Furthermore, GERD therapy, particularly with prokinetic agents and surgery, carries potential risks that must be considered before initiation of therapy. Alternative diagnoses, pretreatment diagnostic testing, and desired treatment outcomes should be considered before initiating GERD therapy. Cessation of empiric GERD therapy should be considered, particularly if treatment does not result in the desired clinical outcome.

Effects of pantoprazole on ulcer healing delay associated with NSAID treatment

Nonsteroidal anti-inflammatory drugs delay gastric ulcer healing, and the ability of proton pump inhibitors to counteract this detrimental effect is debated. This study evaluates the effects of pantoprazole on experimental gastric ulcer healing in the presence of indomethacin. Rats with acetic-acid-induced gastric ulcers were orally treated for 3 or 7 days with pantoprazole (15 micromol/kg/day) or famotidine (20 micromol/kg/day), alone or in combination with indomethacin (3 micromol/kg/day). Ulcerated tissues were processed to assess ulcer area, malondialdehyde, proliferating cell nuclear antigen (PCNA) and cleaved caspase-3. Experiments on pylorus-ligated rats indicated that pantoprazole and famotidine were employed at equivalent inhibitory doses on gastric acid secretion (-67.9% and -64.5%, respectively). Indomethacin delayed ulcer healing both at days 3 and 7 (+22 and +35 mm(2) vs control ulcer, respectively). At day 3, pantoprazole was more effective than famotidine in promoting ulcer healing in indomethacin-treated animals (-53.6 and -31.6 mm(2) vs indomethacin, respectively). Malondialdehyde levels and caspase-3 activation in ulcers were increased by indomethacin (+79% and +3.7 folds vs control ulcer, respectively), and these effects were counteracted by pantoprazole (-77.9% and -3.5 folds vs indomethacin, respectively), but not famotidine. Increments of ulcer PCNA expression (+2.5 folds vs normal) were enhanced further by pantoprazole or famotidine, alone or in combination with indomethacin (+8.6 and +10.3 folds vs normal, respectively). Similar results were obtained after 7-day treatments of ulcerated animals with test drugs. It is concluded that, along with acid suppression, pantoprazole exerts acid-independent effects on ulcer healing, which can be ascribed to a decrease in tissue oxidation and apoptosis.

Clostridium difficile colitis: wash your hands before stopping the proton pump inhibitor

Proton pump inhibitors (PPIs) have revolutionized the management of acid-related disorders. The potential adverse effects related to PPI use fall into four main categories: idiosyncratic reactions, drug-drug interactions, drug-induced reflex hypergastrinemia, and drug-induced hypochlorhydria. Clostridium difficile (C. difficile) colitis, an epidemic of major importance among hospitalized individuals, is potentially facilitated by the fourth mechanism in PPI users. This article interprets the results of the accompanying study by Aseeri et al. that demonstrated a positive association between PPI exposure and C. difficile colitis by examining the findings according to the Bradford Hill criteria. Instead of stopping PPIs when patients are admitted to hospital, I propose continuing the therapy at the lowest effective maintenance dose and adhering to careful barrier nursing and hand washing among patients.

Proton pump inhibitors: an update of their clinical use and pharmacokinetics

BACKGROUND

Proton pump inhibitors (PPIs) represent drugs of first choice for treating peptic ulcer, Helicobacter pylori infection, gastrooesophageal reflux disease, nonsteroidal anti-inflammatory drug (NSAID)-induced gastrointestinal lesions (complications), and Zollinger-Ellison syndrome.

RESULTS

The available agents (omeprazole/esomeprazole, lansoprazole, pantoprazole, and rabeprazole) differ somewhat in their pharmacokinetic properties (e.g., time-/dose-dependent bioavailability, metabolic pattern, interaction potential, genetic variability). For all PPIs, there is a clear relationship between drug exposure (area under the plasma concentration/time curve) and the pharmacodynamic response (inhibition of acid secretion). Furthermore, clinical outcome (e.g., healing and eradication rates) depends on maintaining intragastric pH values above certain threshold levels. Thus, any changes in drug disposition will subsequently be translated directly into clinical efficiency so that extensive metabolizers of CYP2C19 will demonstrate a higher rate of therapeutic nonresponse.

CONCLUSIONS

This update of pharmacokinetic, pharmacodynamic, and clinical data will provide the necessary guide by which to select between the various PPIs that differ-based on pharmacodynamic assessments-in their relative potencies (e.g., higher doses are needed for pantoprazole and lansoprazole compared with rabeprazole). Despite their well-documented clinical efficacy and safety, there is still a certain number of patients who are refractory to treatment with PPIs (nonresponder), which will leave sufficient space for future drug development and clinical research.

Predictable prolonged suppression of gastric acidity with a novel proton pump inhibitor, AGN 201904-Z

BACKGROUND

AGN 201904-Z is a new, slowly absorbed, acid-stable pro-proton pump inhibitor (pro-PPI) rapidly converted to omeprazole in the systemic circulation giving a prolonged residence time.

AIM

To investigate pharmacodynamics and pharmacokinetics of AGN 201904-Z compared to esomeprazole.

METHODS

A randomized, open-label, parallel group, investigator-blinded intragastric pH study was conducted in 24 healthy Helicobacter pylori negative male volunteers. AGN 201904-Z enteric-coated capsules (600 mg/day) or esomeprazole delayed-release tablets (40 mg/day) were administered for 5 days. Twenty-four-hour intragastric pH recordings were acquired at baseline, days 1, 3 and 5 with blood levels of omeprazole, AGN 201904-Z and gastrin.

RESULTS

On day 1, median nocturnal pH and proportion of nocturnal time with pH >or=4 and 24-h and nocturnal time pH >or=5 were significantly higher with AGN 201904-Z than esomeprazole. At day 5, 24-h and median nocturnal pH were significantly higher for AGN 201904-Z than esomeprazole (P < 0.0001). There was also a marked reduction in periods of nocturnal pH <4.0. Area under curve of the AGN 201904-Z active metabolite (omeprazole) in the blood was twice that of esomeprazole at day 5.

CONCLUSIONS

AGN 201904-Z produced a significantly greater and more prolonged acid suppression than esomeprazole, and nocturnal acid suppression was more prolonged over all 5 days. AGN 201904-Z should provide true once-a-day treatment and better clinical efficacy than current PPIs.

The gastric HK-ATPase: structure, function, and inhibition

The gastric H,K-ATPase, a member of the P(2)-type ATPase family, is the integral membrane protein responsible for gastric acid secretion. It is an alpha,beta-heterodimeric enzyme that exchanges cytoplasmic hydronium with extracellular potassium. The catalytic alpha subunit has ten transmembrane segments with a cluster of intramembranal carboxylic amino acids located in the middle of the transmembrane segments TM4, TM5,TM6, and TM8. Comparison to the known structure of the SERCA pump, mutagenesis, and molecular modeling has identified these as constituents of the ion binding domain. The beta subunit has one transmembrane segment with N terminus in cytoplasmic region. The extracellular domain of the beta subunit contains six or seven N-linked glycosylation sites. N-glycosylation is important for the enzyme assembly, maturation, and sorting. The enzyme pumps acid by a series of conformational changes from an E(1) (ion site in) to an E(2) (ion site out) configuration following binding of MgATP and phosphorylation. Several experimental observations support the hypothesis that expulsion of the proton at 160 mM (pH 0.8) results from movement of lysine 791 into the ion binding site in the E(2)P configuration. Potassium access from the lumen depends on activation of a K and Cl conductance via a KCNQ1/KCNE2 complex and Clic6. K movement through the luminal channel in E(2)P is proposed to displace the lysine along with dephosphorylation to return the enzyme to the E(1) configuration. This enzyme is inhibited by the unique proton pump inhibitor class of drug, allowing therapy of acid-related diseases.

Proton pump inhibitors: do differences in pharmacokinetics translate into differences in clinical outcomes?

Acid-related disorders are common management problems in clinical practice. The key to effective management is successful suppression of gastric acid production. Proton pump inhibitors (PPIs) are the most potent acid suppressants available and are significantly more effective than histamine H(2) receptor antagonists. Although PPIs are highly effective as a class, differences in their pharmacokinetics, such as bioavailability, elimination half-life and metabolism, may translate into differences in clinical outcomes. A new immediate-release omeprazole has been introduced, which allows rapid absorption. This has been shown to produce significantly better nocturnal gastric acid control than delayed-release tablets. The bioavailability of rabeprazole on day 1 is greater than with other PPIs, and this may translate into faster onset of symptom relief for patients with gastro-oesophageal reflux disease. On the other hand, the bioavailability of esomeprazole increases 3-fold at day 5, and it has been shown that on day 5, esomeprazole provided significantly more effective control of gastric acid than other PPIs. The exact clinical significance of these observations remains to be determined. There is genetic polymorphism in PPI metabolism via cytochrome P450 2C19. In Helicobacter pylori eradication, a significantly lower eradication rate was seen in extensive metabolisers with omeprazole and lansoprazole but not with rabeprazole. The oesophagitis healing rate was lower in extensive metabolisers with lansoprazole but not with rabeprazole. The currently available PPIs have short elimination half-lives ranging from 1 to 1.5 hours. Tenatoprazole is a new PPI that has a 5- to 7-fold longer elimination half-life than current PPIs. It could be potentially more useful for the treatment of gastro-esophageal reflux disease and nocturnal acid breakthrough than other PPIs.

Systematic expression profiling of the gastric H+/K+ ATPase in human tissue

OBJECTIVE

The potassium-competitive acid blockers (P-CABs), comprise a new, innovative group of competitive and reversible inhibitors of the gastric H+/K+ ATPase. Our aim was to identify sites of expression of the H+/K+ ATPase that are potential targets of these compounds by examining the expression profile of the gastric H+/K+ ATPase in the human body from a broad range of tissues.

MATERIAL AND METHODS

Expression profiling was done by quantitative mRNA analysis (TaqMan PCR). Tissues that were mRNA-positive for the alpha subunit were investigated further by Western blot and immunohistochemistry (IHC) for the presence of gastric H+/K+ ATPase protein.

RESULTS

In addition to the very high expression levels in the stomach, the adrenal gland, cerebellum and pancreas gave unexpectedly positive mRNA signals for the alpha subunit of gastric H +/K+ ATPase. However, they were negative for mRNA of the beta subunit, and Western blot and IHC were negative for alpha and beta subunit protein. Another group of tissues with low alpha subunit mRNA expression including the frontal cortex, cortex grey matter, testis, thymus and larynx submucosa were also found negative for both alpha and beta subunit protein. In contrast to mouse kidney, no gastric H+/K+ ATPase could be detected in human kidney.

CONCLUSIONS

We therefore conclude that the only organ in humans expressing significant levels of the P-CAB target gastric H+/K+ ATPase is the stomach.

Treatment options in pediatric GERD

Gastroesophageal reflux (GER) is a common physiologic phenomenon in infants and children. GER that results in symptoms or complications--hence the evolution to GER disease (GERD)--warrants targeted evaluation and appropriate treatment. Judicious use of acid-suppression therapy remains the mainstay of pharmacologic treatment of GERD. However, recognition of treatment goals and potentials risks of acid suppression must be considered prior to initiation of therapy. The role of surgical intervention for GERD remains limited.

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.

Analysis of the gastric H,K ATPase for ion pathways and inhibitor binding sites

New models of the gastric H,K ATPase in the E1K and E2P states are presented as the first structures of a K+ counter-transport P2-type ATPase exhibiting ion entry and exit paths. Homology modeling was first used to generate a starting conformation from the srCa ATPase E2P form (PDB code 1wpg) that contains bound MgADP. Energy minimization of the model showed a conserved adenosine site but nonconserved polyphosphate contacts compared to the srCa ATPase. Molecular dynamics was then employed to expand the luminal entry sufficiently to allow access of the rigid K+ competitive naphthyridine inhibitor, Byk99, to its binding site within the membrane domain. The new E2P model had increased separation between transmembrane segments M3 through M8, and addition of water in this space showed not only an inhibitor entry path to the luminal vestibule but also a channel leading to the ion binding site. Addition of K+ to the hydrated channel with molecular dynamics modeling of ion movement identified a pathway for K+ from the lumen to the ion binding site to give E2K. A K+ exit path to the cytoplasm operating during the normal catalytic cycle is also proposed on the basis of an E1K homology model derived from the E12Ca2+ form of the srCa ATPase (PDB code 1su4). Autodock analyses of the new E2P model now correctly discriminate between high- and low-affinity K+ competitive inhibitors. Finally, the expanded luminal vestibule of the E2P model explains high-affinity ouabain binding in a mutant of the H,K ATPase [Qiu et al. (2005) J. Biol. Chem. 280, 32349-32355].

On-demand therapy for gastroesophageal reflux disease

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

Adéquation aux recommandations des prescriptions des inhibiteurs de la pompe à protons dans un service de médecine interne

INTRODUCTION

Proton pump inhibitors (PPIs) are an efficient therapy, being widely used by physicians. In 2004, cost of PPIs' therapy was as high as 748 millions of euros (for The Caisse primaire d'Assurance Maladie) in France. Although validated indications of PPIs are well known, numerous un-necessary prescriptions of PPIs are common. The aim of this prospective study was to evaluate PPIs' prescriptions of patients in a department of internal medicine.

PATIENTS AND METHODS

This is a 12-week assessment of medical charts of patients, receiving PPI therapy in patients in our department of internal medicine. Data were collected by a standardized questionnaire, with regards to: PPIs' nature and regimen, PPIs' indications as well as duration of therapy.

RESULTS

The medical charts of 729 consecutive patients, with a mean age of 67 years, were collected. Two hundred (and) twenty-four patients (30.7%) received PPI therapy; 157 of these patients were given PPI before admission in our department. Omeprazole was used in 71% of patients. Duration of PPI therapy was over one year in 45% of cases. Thirty-five per cent of family physicians' PPI prescription were validated and 23.8% of those of physicians working in the department of internal medicine. The main non-conform PPI's indications, by family physicians and internists were as follows: prevention of hemorrhagic risk of anti-platelet agent (21 vs 16.4%), anticoagulant (17.8 vs 16.4%), steroids (8.3 vs 13.4%) or non-steroid anti-inflammatory therapy without risk factor (1.9 vs 9%). Finally, in patients receiving PPI therapy before admission, this therapy was maintained in 76% of cases.

CONCLUSION

This prospective study confirms the frequent prescription of PPI therapy in a department of internal medicine (31% of patients). It also underscores the importance of PPIs' use by family physicians and physicians working in a department of internal medicine; this series further highlights the difficulties to interrupt this well tolerated therapy. To date, PPI therapy should be prescribed with a cautious consideration of cost and benefit.