The clinical importance of proton pump inhibitor pharmacokinetics

Different dosages of vonoprazan for gastroesophageal reflux disease: study protocol for a pragmatic, crossover-cluster, randomized controlled trial with patient preference arms

BACKGROUND

Vonoprazan results in more potent acid suppression for gastroesophageal reflux disease (GERD) than proton pump inhibitors. It has only been approved for treating erosive esophagitis in China, but 30-40% of GERD patients cannot achieve the goal of treatment with vonoprazan 20 mg daily. This study aims to investigate whether vonoprazan could relieve the symptoms of Chinese patients with non-erosive reflux disease (NERD) and whether increased dosage or different times of dosing could increase the response rate of GERD.

METHODS

This study is a pragmatic, open-label, crossover-cluster, randomized controlled trial with patient preference arms. Two thousand eight hundred eighty patients with GERD from 48 hospitals in China will be enrolled. These hospitals will be divided into a compulsory randomization cluster (24 hospitals) and a patient preference cluster (24 hospitals). Patients in the compulsory randomization cluster will be randomized to three regimens according to the crossover-cluster randomization. Patients in the patient preference cluster may choose to receive any regimen if they have a preference; otherwise, patients will be randomly assigned. The three treatment regimens will last 4 weeks, including (1) vonoprazan 20 mg p.o. after breakfast, (2) vonoprazan 20 mg p.o. after dinner, and (3) vonoprazan 20 mg p.o. after breakfast and after dinner. Patients will attend a baseline visit, a 4-week e-diary, a fourth-week visit, and a sixth-month visit online. The primary outcome is the symptom relief rate of all patients after 4-week therapy. Secondary outcomes include the healing rate of EE patients, the severity of symptoms, compliance with the therapy at the fourth-week follow-up visit, recurrent symptoms, and the frequency of self-conscious doctor visits at the sixth-month follow-up visit.

DISCUSSION

This trial will explore the effectiveness of different regimens of vonoprazan that will be implemented with GERD patients in China. The randomization with patient preferences considered and the crossover-cluster component may improve the robustness and extrapolation of study conclusions.

TRIAL REGISTRATION

https://www.chictr.org.cn ChiCTR2300069857. Registered on 28 March 2023.

PROTOCOL VERSION

February 18, 2023, Version 2.

Night-time gastric acid suppression by tegoprazan compared to vonoprazan or esomeprazole

AIM

Nocturnal acid breakthrough has been considered an unmet need of proton pump inhibitors. Tegoprazan, a novel potassium-competitive acid blocker, is expected to show improved properties for this unmet need. This study was aimed to compare night-time acid suppression by tegoprazan with that by vonoprazan or esomeprazole, and to explore the effect of CYP2C19 phenotypes on acid-suppressive effects.

METHODS

A randomized, open-label, three-period, six-sequence crossover study was conducted. A single oral dose of tegoprazan 50 mg, vonoprazan 20 mg or esomeprazole 40 mg was administered at night in each period. Continuous intragastric pH was monitored at baseline and after each dosing.

RESULTS

16 healthy subjects (6 CYP2C19 extensive metabolizers, 5 intermediate metabolizers, 5 poor metabolizers) completed the study. After a single dose of tegoprazan, intragastric pH increased more rapidly to over 4 at approximately 1 hour compared to the other treatments, and elevated intragastric pH was maintained stably at night. Tegoprazan exhibited night-time acid suppression for slightly but not significantly longer than vonoprazan, and greater than esomeprazole; % Time pH ≥4 at night-time was 66.0%, 60.5% and 36.1% for tegoprazan, vonoprazan and esomeprazole, respectively. Night-time acid suppression by tegoprazan and vonoprazan was not dependent on CYP2C19 phenotypes, while that by esomeprazole tended to be influenced by CYP2C19 phenotypes.

CONCLUSIONS

Tegoprazan produced more rapid, potent and well sustained night-time acid suppression versus vonoprazan or esomeprazole when administered at night. Furthermore, tegoprazan showed no CYP2C19 phenotype dependency in acid suppression. It suggests the potential of tegoprazan, especially in preventing nocturnal acid breakthrough.

CYP2C19 Phenotype and Risk of Proton Pump Inhibitor-Associated Infections

OBJECTIVES

Proton pump inhibitors (PPIs) are often used in pediatrics to treat common gastrointestinal disorders, and there are growing concerns for infectious adverse events. Because CYP2C19 inactivates PPIs, genetic variants that increase CYP2C19 function may decrease PPI exposure and infections. We tested the hypothesis that CYP2C19 metabolizer phenotypes are associated with infection event rates in children exposed to PPIs.

METHODS

This retrospective biorepository cohort study included individuals aged 0 to 36 months at the time of PPI exposure. Respiratory tract and gastrointestinal tract infection events were identified by using International Classification of Diseases codes in the year after the first PPI mention. Variants defining CYP2C19 *2, *3, *4, *8, *9, and *17 were genotyped, and all individuals were classified as CYP2C19 poor or intermediate, normal metabolizers (NMs), or rapid or ultrarapid metabolizers (RM/UMs). Infection rates were compared by using univariate and multivariate analyses.

RESULTS

In all, 670 individuals were included (median age 7 months; 44% girls). CYP2C19 NMs (n = 267; 40%) had a higher infection rate than RM/UMs (n = 220; 33%; median 2 vs 1 infections per person per year; P = .03). There was no difference between poor or intermediate (n = 183; 27%) and NMs. In multivariable analysis of NMs and RM/UMs adjusting for age, sex, PPI dose, and comorbidities, CYP2C19 metabolizer status remained a significant risk factor for infection events (odds ratio 0.70 [95% confidence interval 0.50-0.97] for RM/UMs versus NMs).

CONCLUSIONS

PPI therapy is associated with higher infection rates in children with normal CYP2C19 function than in those with increased CYP2C19 function, highlighting this adverse effect of PPI therapy and the relevance of CYP2C19 genotypes to PPI therapeutic decision-making.

Proton pump inhibitors: from CYP2C19 pharmacogenetics to precision medicine

Introduction: Proton Pump inhibitors (PPIs) are commonly used for a variety of acid related disorders. Despite the overall effectiveness and safety profile of PPIs, some patients do not respond adequately or develop treatment related adverse events. This variable response among patients is in part due to genotype variability of CYP2C19, the gene encoding the CYP450 (CYP2C19) isoenzyme responsible for PPIs metabolism.

Areas covered: This article provides an overview of the pharmacokinetics and mechanism of action of the currently available PPIs, including the magnitude of CYPC19 contribution to their metabolism. Additionally, the role of CYP2C19 genetic variability in the therapeutic effectiveness or outcomes of PPI therapy is highlighted in details, to provide supporting evidence for the potential value of CYP2C19 genotype-guided approaches to PPI drug therapy.

Expert opinion: There is a large body of evidence describing the impact of CYP2C19 variability on PPIs and its potential role in individualizing PPI therapy, yet, CYP2C19 pharmacogenetics has not been widely implemented into clinical practice. More data are needed but CYP2C19 genotype-guided dosing of PPIs is likely to become increasingly common and is expected to improve clinical outcomes, and minimize side effects related to PPIs.

Institutional profile: University of Florida Health Personalized Medicine Program

The University of Florida (UF) Health Personalized Medicine Program launched in 2012 with CYP2C19 genotyping for clopidogrel response at UF Health Shands Hospital. We have since expanded CYP2C19 genotyping to UF Health Jacksonville and established the infrastructure at UF Health to support clinical implementation for five additional gene-drug pairs: TPMT-thiopurines, IFNL3 (IL28B)-PEG IFN-α-based regimens, CYP2D6-opioids, CYP2D6/CYP2C19-antidepressants and CYP2C19-proton pump inhibitors. We are contributing to the evidence based on outcomes with genotype-guided therapy through pragmatic studies of our clinical implementations. In addition, we have developed a broad array of educational programs for providers, trainees and students that incorporate personal genotype evaluation to enhance participant learning.

Proton Pump Inhibitors Decrease Soluble fms-Like Tyrosine Kinase-1 and Soluble Endoglin Secretion, Decrease Hypertension, and Rescue Endothelial Dysfunction

Preeclampsia is a severe complication of pregnancy. Antiangiogenic factors soluble fms-like tyrosine kinase-1 (sFlt-1) and soluble endoglin are secreted in excess from the placenta, causing hypertension, endothelial dysfunction, and multiorgan injury. Oxidative stress and vascular inflammation exacerbate the endothelial injury. A drug that can block these pathophysiological steps would be an attractive treatment option. Proton pump inhibitors (PPIs) are safe in pregnancy where they are prescribed for gastric reflux. We performed functional studies on primary human tissues and animal models to examine the effects of PPIs on sFlt-1 and soluble endoglin secretion, vessel dilatation, blood pressure, and endothelial dysfunction. PPIs decreased sFlt-1 and soluble endoglin secretion from trophoblast, placental explants from preeclamptic pregnancies, and endothelial cells. They also mitigated tumor necrosis factor-α-induced endothelial dysfunction: PPIs blocked endothelial vascular cell adhesion molecule-1 expression, leukocyte adhesion to endothelium, and disruption of endothelial tube formation. PPIs decreased endothelin-1 secretion and enhanced endothelial cell migration. Interestingly, the PPI esomeprazole vasodilated maternal blood vessels from normal pregnancies and cases of preterm preeclampsia, but its vasodilatory effects were lost when the vessels were denuded of their endothelium. Esomeprazole decreased blood pressure in a transgenic mouse model where human sFlt-1 was overexpressed in placenta. PPIs upregulated endogenous antioxidant defenses and decreased cytokine secretion from placental tissue and endothelial cells. We have found that PPIs decrease sFlt-1 and soluble endoglin secretion and endothelial dysfunction, dilate blood vessels, decrease blood pressure, and have antioxidant and anti-inflammatory properties. They have therapeutic potential for preeclampsia and other diseases where endothelial dysfunction is involved.

Pharmacogenomic testing: the case for CYP2C19 proton pump inhibitor gene-drug pairs

The use of proton pump inhibitors (PPIs) in the treatment of gastroesophageal reflux and related diseases is increasing, especially in the pediatric population. Prolonged use of PPIs has been associated with several adverse effects, including potentially life-threatening gastric and respiratory infections, which are related to dose or to the degree of gastric acid suppression. Genetic variation in the CYP2C19 gene gives rise to poor and extensive metabolizer phenotypes, which influence PPI clearance, efficacy and exposure. A recent paper linked lansoprazole-associated respiratory infections in children with the poor metabolizer phenotype. The case is made for implementing pharmacogenomic testing for the CYP2C19-PPI gene-drug pair and to dose accordingly in order to minimize PPI-associated infections.

The role of the pharmacist in the selection and use of over-the-counter proton-pump inhibitors

Background Heartburn and other symptoms of gastro-oesophageal reflux occur in ~30 % of survey respondents in multiple countries worldwide. Heartburn and acid regurgitation are common complaints in the pharmacy, where patients frequently seek relief through medication and advice. The growing number of proton-pump inhibitors available in the over-the-counter setting provides an efficacious choice to patients experiencing frequent heartburn. Pharmacists can assist patients in their treatment decisions whilst inquiring about alarm symptoms that should prompt a physician referral. Aim of the review Provide pharmacists with a review of current clinical research and expert guidelines on use of over-the-counter proton-pump inhibitors. Methods This narrative review was conducted to identify publications relevant to the following themes: overview of available treatments for frequent episodes of heartburn/acid regurgitation; treatment algorithms providing guidance on when to use over-the-counter proton-pump inhibitors; and the role of the pharmacist in the use of over-the-counter proton-pump inhibitors. Results Frequent symptoms of acid reflux, such as heartburn and acid regurgitation, can interfere substantially with daily life activities. Proton-pump inhibitors are the most efficacious treatment for frequent reflux symptoms and are recommended as an appropriate initial treatment in uncomplicated cases. Proton-pump inhibitors have varying pharmacokinetics and pharmacodynamics across the class; 20 mg esomeprazole has higher bioavailability and exposure than over-the-counter omeprazole, for example. However, differences in clinical efficacy for symptom relief have not been demonstrated. The safety and tolerability of proton-pump inhibitors have been well established in clinical trial and post-marketing settings, and use of a short regimen is associated with a very low likelihood of missing a more serious condition. Pharmacists can assist patients with accurate self-diagnosis by asking short, simple questions to characterize the nature, severity, and frequency of symptoms. Additionally, pharmacists can inquire about alarm symptoms that should prompt referral to a physician. Pharmacists should inform those patients for whom over-the-counter proton-pump inhibitors are appropriate on their proper use. Conclusion Over-the-counter proton-pump inhibitors have a valuable role in the treatment of frequent heartburn. Pharmacists have the opportunity to guide patients through selection of the best treatment option for their symptoms.

Effect of icosapent ethyl (eicosapentaenoic acid ethyl ester) on omeprazole plasma pharmacokinetics in healthy adults

Background

Icosapent ethyl (IPE) is a high-purity prescription form of eicosapentaenoic acid ethyl ester approved by the US Food and Drug Administration as an adjunct to diet to reduce triglyceride levels in adult patients with severe hypertriglyceridemia. Patients with high serum triglycerides may be taking concurrent medications for associated conditions such as obesity and/or diabetes mellitus.

Objective

To evaluate the effect of IPE on the plasma pharmacokinetics (PK) of omeprazole, a commonly used proton pump inhibitor and a substrate of cytochrome P450 (CYP) 2C19.

Study design

Omeprazole (40 mg/day for 7 days) was administered orally without and with 4 g/day IPE at steady state. The primary PK endpoint was area under the concentration-time curve from time 0 to 24 h (AUC_0–24); secondary endpoints included maximum observed plasma concentration (C_max). Safety was monitored in all subjects who received one or more dose(s) of the study drug.

Participants

Thirty healthy adult subjects were enrolled and 28 completed the study.

Results

IPE 4 g/day at steady state did not significantly change the AUC_0–24 or C_max of omeprazole when co-administered at 40 mg/day to steady state. The ratios of least squares geometric means (90 % confidence interval) for AUC_0–24 and C_max (omeprazole with IPE vs. omeprazole alone) were 0.84 (76.0–91.9) and 1.01 (87.4–116.3), respectively. There were no clinically significant findings from laboratory tests, vital signs, or physical examinations.

Conclusions

At steady-state concentrations, IPE 4 g/day did not inhibit the AUC_0–24 or C_max of omeprazole 40 mg/day, a CYP2C19 substrate. Co-administration of IPE with omeprazole was safe and well tolerated.

Therapeutic management of uncomplicated gastroesophageal reflux disease in france in 2005: Potential cost savings of omeprazole substitution

BACKGROUND

Proton pump inhibitors (PPIs) cost the French health care system >€1 billion in 2005, and ~50% of PPI prescriptions were for the treatment of gastroesophageal reflux disease (GERD).

OBJECTIVES

This study aimed to describe the current use of PPIs for GERD, to estimate the total annual costs of treatment, and to evaluate the economic impact of the various possible substitutions among PPIs available for this indication in France.

METHODS

Data from a sample of patients aged ≥20 years who visited their general practitioner (GP) at least once in 2005 for uncomplicated, symptomatic GERD were retrieved from the Thales database (a group of 1200 representative GPs connected to a computerized network). Costs of the prescriptions presented for reimbursement and costs of those reimbursed by the French health care insurance system were analyzed. We then evaluated the economic consequences of replacing full-dose generic omeprazole (after substitution from brand-name omeprazole by the pharmacists) with other compounds that are indicated for mild symptoms at half dose (ie, lansoprazole 15 mg, pantoprazole 20 mg, rabeprazole 10 mg, and esomeprazole 20 mg). The results were adjusted to account for the proportions of patients who had full health care coverage and the treatment duration as reported in the database. RESULTS are presented from the perspective of the French health care insurance system.

RESULTS

In 2005, a total of 122,571 patients (mean age, 55.7 years; 45.5% men; 13.8% with a history of at least 1 gastrointestinal disorder) met the inclusion criteria. Extrapolated to the French population, this sample corresponded to ≈5.7 million people (ie, 13% of the adult population who visited a GP during the year). PPIs were prescribed as first-line treatment for GERD in 84.1% of the consultations (14.3% in association with other antiulcer drugs). Omeprazole, as a proprietary or generic drug, was prescribed most often (78.9%) and at full dose (20 mg), while other compounds (lansoprazole, pantoprazole, rabeprazole, and esomeprazole) were prescribed at half dose in 64.3% of cases. The extrapolated annual cost of PPIs reimbursed for this indication was €465.02 million at a mean reimbursement level of 72.7%. Brand-name omeprazole still accounted for ≈11% of the total cost reimbursed. Complete replacement of brand-name omeprazole with its generic counterpart would have reduced costs by €18.35 million (a decrease of 4.3% in the total reimbursed expenditure). The switch from generic full-dose omeprazole to a half dose of other PPIs would have allowed further savings ranging from €2.59 million (with lansoprazole) to €13.19 million (with pantoprazole).

CONCLUSION

In accordance with recent recommendations for the treatment of uncomplicated GERD and based on the 2006 PPI pricing, switching from branded full-dose omeprazole to generic omeprazole or to the use of half doses of other PPIs may allow cost savings in France.

Exploring the potential effect of polypharmacy on the hematologic profiles of clozapine patients

INTRODUCTION

Clozapine, an atypical antipsychotic with documented efficacy in the management of treatment-resistant schizophrenia, is associated with the risk of adverse hematological outcomes. Of particular concern are reductions in white blood cells (WBC) and absolute neutrophil counts (ANC). Individuals who display moderate leukopenia (3000/mm(3) > WBC ≥ 2000/mm) upon initiation of clozapine therapy are at increased risk of developing agranulocytosis, defined as an ANC less than 500/mm. Complications of agranulocytosis can be severe and include increased risk of infection and mortality.

OBJECTIVES

The primary objective of this study was to examine data on clozapine recipients who experienced adverse drug reactions (ADRs) related to decreases in WBC or ANC and ascertain whether other drugs and/or drug interactions had played a role. The analysis included multiple classes of medications.

METHODS

A retrospective chart review was performed of open and closed medical records of all inpatient recipients of clozapine at a state psychiatric center between January 1, 2004 and June 30, 2011. Laboratory records of patients prescribed clozapine were examined for abnormal WBC counts or ANC. A hematological ADR was considered to have occurred if there was a substantial drop in either WBC or ANC or mild or moderate leukopenia or granulocytopenia. Each episode was analyzed for medications that might have contributed to the ADR. Data were collected for all scheduled and STAT medications started at any point during the clozapine patient's hospitalization. The following seven medication groups, based on the Therapeutic Classification System of the American Hospital Formulary System (AHFS), were chosen for analysis because they were consistently used in the majority of the patient population: antihistamines, anti-infectives, autonomic agents, cardiovascular agents, antipsychotics, vitamins, and gastrointestinal agents. Pearson correlation coefficients were calculated to identify associations between the presence of hematological ADRs and medications administered concomitantly with clozapine.

RESULTS

The following significant correlation coefficients were found between the use of a class of medications and the occurrence of a hematological ADR: antiinfective agents 0.409 (p < 0.01), gastrointestinal agents 0.329 (p < 0.01), and autonomic agents 0.309 (p < 0.01). In the subset of patients who were prescribed a proton-pump inhibitor or ranitidine concomitantly with clozapine, 24/26 (96%) experienced a hematological ADR.

CONCLUSIONS

Autonomic agents, anti-infective agents, and proton pump inhibitors and other gastrointestinal agents were all associated with hematological ADRs when co-prescribed with clozapine. Medications from these classes should be initiated cautiously in patients being treated with clozapine to avoid precipitous drops in ANC or WBC that may increase the risk of agranulocytosis.

Association of CYP2C19 polymorphisms and lansoprazole-associated respiratory adverse effects in children

OBJECTIVE

To determine whether cytochrome P450 (CYP)2C19 haplotype associates with lansoprazole-associated adverse event frequency.

STUDY DESIGN

Respiratory adverse events from a clinical trial of lansoprazole in children with asthma were analyzed for associations with extensive or poor metabolizer (PM) phenotype based on CYP2C19 haplotypes. Carriers of CYP2C19*2, *3, *8, or *9 alleles were PMs; carriers of 2 wild-type alleles were extensive metabolizers (EMs). Plasma concentrations of lansoprazole were determined in PM and EM phenotypes.

RESULTS

The frequency of upper respiratory infection among PMs (n = 45) was higher than that among EMs (n = 91), which in turn was higher than that in placebo subjects (n = 135; P = .0039). The frequency of sore throat (ST) was similarly distributed among EMs and PMs (P = .0015). The OR (95% CI) for upper respiratory infections in PMs was 2.46 (1.02-5.96) (P = .046); for EMs, the OR (95% CI) was 1.55 (0.86-2.79). The OR (95% CI) for ST in EMs and PMs was 2.94 (1.23-7.05, P = .016) vs 1.97 (1.09-3.55, P = .024), respectively. Mean ± SD plasma concentrations of lansoprazole were higher in PMs than in EMs: 207 ± 179 ng/mL vs 132 ± 141 ng/mL (P = .04).

CONCLUSIONS

Lansoprazole-associated upper respiratory infections and ST in children are related in part to CYP2C19 haplotype. Our data suggest that lansoprazole-associated adverse events in children may be mitigated by adjusting the conventional dose in PMs. Additional studies are required to replicate our findings.

Comparison of different regimens of proton pump inhibitors for acute peptic ulcer bleeding

BACKGROUND

Treatment with proton pump inhibitors (PPIs) improves clinical outcomes in patients with peptic ulcer bleeding. However, the optimal dose and route of administration of PPIs remains controversial.

OBJECTIVES

To evaluate the efficacy of different regimens of PPIs in the management of acute peptic ulcer bleeding using evidence from direct comparison randomized controlled trials (RCTs).We specifically intended to assess the differential effect of the dose and route of administration of PPI on mortality, rebleeding, surgical intervention, further endoscopic haemostatic treatment (EHT), length of hospital stay, transfusion requirements and adverse events.

SEARCH METHODS

We searched CENTRAL (in The Cochrane Library 2010, Issue 3), MEDLINE and EMBASE (from inception to September 2010) and proceedings of major gastroenterology meetings (January 2000 to September 2010), without language restrictions. Original investigators were contacted to request missing data.

SELECTION CRITERIA

RCTs that compared at least two different regimens of the same or a different PPI in patients with acute peptic ulcer bleeding, diagnosed endoscopically.

DATA COLLECTION AND ANALYSIS

Two reviewers independently selected studies, extracted data and assessed risk of bias. We synthesized data using the Mantel-Haenszel random-effects method and performed multivariate meta-regression with random permutations based on Monte Carlo simulation. We measured heterogeneity with the I² statistic and Cochrane Q test and assessed publication bias with funnel plots and Egger's test. We graded the overall quality of evidence using the GRADE approach.

MAIN RESULTS

Twenty two RCTs were included; risk of bias was high in 17 and unclear in 5. The main analysis included 13 studies (1716 patients) comparing "high" dose regimens (72-hour cumulative dose > 600 mg of intravenous PPI) to other doses; there was no significant heterogeneity for any clinical outcome. We found low quality evidence that did not exclude a potential reduction or increase in mortality, rebleeding, surgical interventions or endoscopic haemostatic treatment (EHT) with "high" dose regimens. For mortality, pooled risk ratio (RR) was 0.85 (95% confidence interval (CI) 0.47 to 1.54); pooled risk difference (RD) was 0 more deaths per 100 patients treated with "high" dose (95% CI from 1 fewer to 2 more deaths per 100 treated). For rebleeding, pooled RR was 1.27 (95% CI 0.96 to 1.67); pooled RD was 2 more rebleeding events per 100 patients treated with "high" dose (95% CI from 0 fewer to 5 more rebleeding events per 100 treated). For surgical interventions, pooled RR was 1.33 (95% CI 0.63 to 2.77); pooled RD was 1 more surgical intervention per 100 patients treated with "high" dose (95% CI from 1 fewer to 2 more surgical interventions per 100 treated). For further EHT, pooled RR was 1.39 (95% CI 0.88 to 2.18), pooled RD was 2 more events per 100 patients treated with "high" dose PPI (95% CI from 1 fewer to 5 more events per 100 treated). We found moderate quality evidence suggesting no important difference between the two regimens with regards to length of hospital stay (mean difference (MD) 0.26 days; 95% CI -0.08 to 0.6 days) or blood transfusion requirements (MD 0.05 units; 95% CI -0.21 to 0.3 units). There was visual and statistical evidence of "inverse" publication bias for mortality (missing small studies with favourable outcomes for "high" dose), but not for any other outcome. The results were similar for all subgroup analyses (according to risk of bias, geographical location, route of administration for non-"high" dose regimens, continuous infusion vs. bolus administration for intravenous non-"high" regimens group), sensitivity analyses (restriction to patients who had EHT for high risk stigmata, use of different dose thresholds for comparative regimens) and post hoc analyses (inclusion of all studies (N = 22) that compared at least two PPI regimens with different cumulative 72 hour doses; restriction of the previous analysis to patients who had EHT for high risk stigmata). Meta-regression analysis did not show any statistically significant associations between treatment effect (for the outcomes of mortality, rebleeding and surgical intervention) and the three study-level factors that were assessed (geographical location (Asia versus not Asia), route of PPI administration (intravenous versus oral), within-study ratio among the 72-hour cumulative doses of the two PPI regimens).

AUTHORS' CONCLUSIONS

There is insufficient evidence for concluding superiority, inferiority or equivalence of high dose PPI treatment over lower doses in peptic ulcer bleeding.

A Randomized, Controlled, Crossover Trial to Investigate Times to Onset of the Perception of Soothing and Cooling by Over-The-Counter Heartburn Treatments

This was a randomized, controlled, four-way crossover study in 45 subjects with a tendency to suffer from moderate heartburn following some meals. The study was designed to assess the time to onset of the perceived soothing and cooling effects of the alginate raft-forming products, Gaviscon Liquid (peppermint), Gaviscon Double Action Liquid (peppermint) and Gaviscon Powder Formulation (fresh tropical), compared with a non-active sublingual control. All three Gaviscon products provided significantly faster soothing and cooling effects compared with the control. Based on the upper 95% confidence limits for the median, time to onset of soothing was perceived within 3.15 min, 3.08 min and 4.05 min for Gaviscon Liquid, Double Action Liquid and Powder Formulation, respectively. Similarly, time to onset of cooling was perceived within 1.95 min, 1.23 min and 11.22 min for Gaviscon Liquid, Double Action Liquid and Powder Formulation, respectively. The results show that Gaviscon Liquid and Gaviscon Double Action soothe within 3.15 min and cool within 1.95 min.

Molecular mechanism and functional consequences of lansoprazole-mediated heme oxygenase-1 induction

AIM: To investigate the molecular mechanism and functional consequences of heme oxygenase-1 (HO-1) activation by lansoprazole in endothelial cells and macrophages.

METHODS: Expression of HO-1 mRNA was analyzed by Northern blotting. Western blotting was used to determine the HO-1 and ferritin protein levels. NADPH-dependent reactive oxygen species (ROS) formation was measured with lucigenin-enhanced chemiluminescence. HO-1 promoter activity in mouse fibroblasts, stably transfected with a 15-kb HO-1 gene that drives expression of the reporter gene luciferase, was assessed using in vivo bioluminescence imaging.

RESULTS: Lansoprazole increased HO-1 mRNA levels in endothelial cells and HO-1 protein levels in macrophages. In addition, lansoprazole-induced ferritin protein levels in both cell systems. Moreover, induction of the antioxidant proteins HO-1 and ferritin by lansoprazole was followed by a decrease in NADPH-mediated ROS formation. The radical scavenging properties of lansoprazole were diminished in the presence of the HO inhibitor, chromium mesoporphyrin IX. Induction of HO-1 gene expression by lansoprazole was not related to oxidative stress or to the activation of the mitogen-activated protein kinase pathway. However, the phosphatidylinositol 3-kinase inhibitor LY294002 showed a concentration-dependent inhibition of HO-1 mRNA and promoter activity.

CONCLUSION: Activation of HO-1 and ferritin may account for the gastric protection of lansoprazole and is dependent on a pathway blocked by LY294002.

Proton pump inhibitors reduce mycophenolate exposure in heart transplant recipients-a prospective case-controlled study

This prospective study investigates the impact of proton pump inhibitors (PPI) on mycophenolic acid (MPA) pharmacokinetics in heart transplant recipients receiving mycophenolate mofetil (MMF) and tacrolimus. MPA plasma concentrations at baseline (C(0 h)), 30 min (C(0.5 h)), 1(C(1 h)) and 2 h (C(2 h)) were obtained by high-performance liquid chromatography (HPLC) in 22 patients treated with pantoprazole 40 mg and MMF 2000 mg. Measurements were repeated 1 month after pantoprazole withdrawal. A four-point limited-sampling strategy was applied to calculate the MPA area under the curve (MPA-AUC). Predose MPA concentrations with PPI were 2.6 +/- 1.6 mg/L versus 3.4 +/- 2.7 mg/L without PPI (p = ns). Postdose MPA concentrations were lower with PPI at C(0.5 h) (8.3 +/- 5.7 mg/L vs. 18.3 +/- 11.3 mg/L, p = 0.001) and C(1 h) (10.0 +/- 5.6 mg/L vs. 15.8 +/- 8.4 mg/L, p = 0.004), without significant differences at C(2 h) (8.3 +/- 6.5 mg/L vs. 7.6 +/- 3.9 mg/L). The MPA-AUC was significantly lower with PPI medication (51.2 +/- 26.6 mg x h/L vs. 68.7 +/- 30.3 mg x h/L; p = 0.003). The maximum concentration of MPA (MPA-C(max)) was lower (12.2 +/- 7.5 mg/L vs. 20.6 +/- 9.3 mg/L; p = 0.001) and the time to reach MPA-C(max) (t(max)) was longer with PPI (60.0 +/- 27.8 min vs. 46.4 +/- 22.2 min; p = 0.05). This is the first study to document an important drug interaction between a widely used immunosuppressive agent and a class of drugs frequently used in transplant patients. This interaction results in a decreased MMF drug exposure which may lead to patients having a higher risk for acute rejection and transplant vasculopathy.

Comparison of p.o. or i.v. proton pump inhibitors on 72-h intragastric pH in bleeding peptic ulcer

BACKGROUND AND AIMS

After successful endoscopic hemostasis in bleeding peptic ulcer, addition of proton pump inhibitors reduce the rate of recurrent bleeding by maintaining intragastric pH at neutral level. The aim of the present study was to evaluate the effect of various proton pump inhibitors given through different routes on intragastric pH over 72 h after endoscopic hemostasis in bleeding peptic ulcer.

METHODS

Ninety consecutive patients who had successful endoscopic therapy of bleeding peptic ulcer underwent 72-h continuous ambulatory intragastric pH study, were randomly assigned to receive p.o. omeprazole 80 mg bolus followed by 40 mg every 12 h for 72 h or i.v. 80 mg omeprazole followed by infusion 8 mg/h for 72 h. Oral pantoprazole 80 mg bolus followed by 80 mg every 12 h for 72 h or i.v. 80 mg pantoprazole followed by infusion of 8 mg/h for 72 h. Oral rabeprazole 80 mg bolus followed by 40 mg every 12 h for 72 h or i.v. 80 mg rabeprazole followed by infusion 8 mg/h for 72 h. Five patients received no treatment after successful endoscopic therapy and underwent 72-h pH study.

RESULTS

Mean 72-h intragastric pH for p.o. omeprazole was 6.56 versus 6.93 for omeprazole infusion (P = 0.48). Mean 72-h intragastric pH for p.o. pantoprazole was 6.34 versus 6.32 for pantoprazole infusion (P = 0.62). Mean 72-h intragastric pH for rabeprazole p.o. was 6.11 versus 6.18 rabeprazole i.v. (P = 0.55). Mean 72-h pH for the no proton pump inhibitor group was 2.04.

CONCLUSION

There was no significant difference among various proton pump inhibitors given through different routes on raising intragastric pH above 6 for 72 h after successful endoscopic hemostasis in bleeding peptic ulcer.

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.

Population pharmacokinetics of intravenous pantoprazole in paediatric intensive care patients

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

The use of intravenous pantoprazole, a proton pump inhibitor, has been increasing in the paediatric intensive care unit. Despite this increased use, data on the disposition of intravenous pantoprazole in paediatric intensive care patients are very scarce.

WHAT THIS STUDY ADDS

Our population approach has determined the pharmacokinetic parameters of intravenous pantoprazole in paediatric intensive care patients and the relative importance of factors influencing its disposition. Pantoprazole clearance was significantly influenced by developmental changes and by the presence of systemic inflammatory syndrome, hepatic dysfunction and CYP2C19 inhibitors.

AIMS

To characterize the pharmacokinetics of intravenous pantoprazole in a paediatric intensive care population and to determine the influence of demographic factors, systemic inflammatory response syndrome (SIRS), hepatic dysfunction and concomitantly used CYP2C19 inducers and inhibitors on the drug's pharmacokinetics.

METHODS

A total of 156 pantoprazole concentration measurements from 20 patients (10 days to 16.4 years of age) at risk for or with upper gastrointestinal bleeding, who received pantoprazole doses ranging from 19.9 to 140.6 mg/1.73 m(2)/day, were analysed using a population pharmacokinetic approach (nonmem program).

RESULTS

The best structural model for pantoprazole was a two-compartment model with zero order infusion and first-order elimination. Body weight, SIRS, age, hepatic dysfunction and presence of CYP2C19 inhibitors were significant covariates affecting clearance (CL), accounting for 75% of interindividual variability. Only body weight significantly influenced central volume of distribution (V(c)). In the final population model, the estimated CL and V(c) were 5.28 l h(-1) and 2.22 l, respectively, for a typical 5-year-old child weighing 20 kg. Pantoprazole CL increased with weight and age, whereas the presence of SIRS, CYP2C19 inhibitors and hepatic dysfunction, when present separately, significantly decreased pantoprazole CL by 62.3, 65.8 and 50.5%, respectively. For patients aged between 6 months and 5 years without SIRS, CYP2C19 inhibitor or hepatic dysfunction, the predicted pantoprazole CL is faster than that reported in adults.

CONCLUSION

These results provide important information for physicians regarding selection of a starting dose and dosing regimens of pantoprazole for paediatric intensive care patients based on factors frequently encountered in this population.

Constituents and antiulcer effect of Alchornea glandulosa: activation of cell proliferation in gastric mucosa during the healing process

Alchornea glandulosa (Euphorbiaceae) is a plant used in folk medicine as an antiulcer agent. Rats pretreated with methanolic extract obtained from the leaves of A. glandulosa (AG) showed a dose-dependent effect and significant reduction of gastric ulcers induced by absolute ethanol at the doses of 500 (57%) and 1000 mg/kg (85%) in relation to the control group. Pretreatment of mice with AG (500, 1000 mg/kg, p.o.) showed dose-dependent activity and significantly decreased the severity of lesions caused by HCl/ethanol and by non steroidal anti inflammatory drug-induced gastric lesions. Pretreatment with AG also induced antisecretory action via local and systemic routes and a significant decrease in the total gastric acid content. The gastroprotective effects of AG involved the participation of nitric oxide and increased levels of endogenous sulfhydryl compounds, which are defensive mechanisms of the gastrointestinal mucosa against aggressive factors. The ability of AG to heal gastric ulcers was evaluated after 14 consecutive days of treatment. The results showed that single oral administrations of AG (250 mg/kg/once daily) potently stimulates gastric epithelial cell proliferation that contributes to the accelerated healing of gastric ulcers induced by acetic acid. In addition, no subacute toxicity (body weight gain, vital organs, and serum biochemical parameters) was observed during treatment with AG. Phytochemical investigation of AG led to the isolation of myricetin-3-O-alpha-L-rhamnopyranoside, quercetin-3-O-alpha-L-arabinopyranoside, quercetin-3-O-beta-D-galactopyranoside, quercetin, amentoflavone, methyl gallate, gallic acid, and pterogynidine. We also established the phytochemical profile of AG with the quantification of total phenolic compounds. These compounds may contribute to the observed antiulcerogenic effects of AG.

Hydroxyl radical scavenging reactivity of proton pump inhibitors

In addition to the established control of acid secretion of the class of proton pump inhibitors (PPI) reactivity from the pyridyl methyl sulphinyl benzimidazole type a second independent anti-inflammatory reactivity was observed in vitro. This inhibitory reactivity was clearly noticed using three different assays where the aggressive hydroxyl radicals were successfully trapped in a concentration dependent manner. There is unequivocal evidence that the proton pump inhibitors having the sulphoxide group are able to scavenge hydroxyl radicals which are generated during a Fenton reaction. By way of contrast, the corresponding thioethers were substantially less active. No detectable effect was seen in the superoxide radical scavenging system. In conclusion, pantoprazole as well as the other proton pump inhibitors have a pronounced inhibitory reactivity towards hydroxyl radicals.

Possible Interethnic Differences in Omeprazole Pharmacokinetics

BACKGROUND AND OBJECTIVE

Considerable ethnic differences have been reported in the incidence of the poor metaboliser (PM) genotype of cytochrome P450 (CYP) 2C19. The frequency of this genotype was found to be much higher in Oriental persons (13-23%) than in American or European populations (3-5%). There are, however, no valid data published for Arabic subjects. The present study was conducted to evaluate pharmacokinetic parameters of omeprazole after a single dose in healthy Jordanian Arabic subjects and to compare the results with data published for other populations.

METHODS

Seventy-four healthy male Jordanian Arabic volunteers contributed to the study, which was performed at Al Essra Hospital in Amman, Jordan. After an overnight fast, omeprazole was administered as a single Losec 20mg capsule. A total of 20 blood samples were collected over a 10-hour period after administration. Omeprazole pharmacokinetic parameters were determined from the plasma concentration-time profiles using the WinNonlin software. Kolmogorov-Smirnov's test and probit plots of omeprazole area under the plasma concentration-time curve (AUC) data were used to analyse the frequency distribution of phenotypic data.

RESULTS

The mean pharmacokinetic parameters and their corresponding coefficient of variation (CV%) for peak plasma concentration (Cmax), AUC from time zero to infinity (AUCinfinity), time to reach Cmax (tmax), apparent oral clearance (CL/F) and elimination half-life (t(1/2)) were 314.96 ng/mL (56%), 923.2 ng . h/mL (108.6%), 2.1h (44%), 0.66 L/h/kg (92%) and 1.5 h (56.6%), respectively. Interindividual differences in the current study were high for all pharmacokinetic parameters, yet comparable to CVs reported in nonphenotyped subjects identified within other ethnic groups (40.3-159% for AUC and 39-48.2% for Cmax). The frequency distribution of all parameters, particularly the AUC, was shown to be trimodal. This has proposed the presence of three distinct phenotypes, designated as extensive metabolisers (EMs), slow-extensive metabolisers (SEMs), and PMs, with corresponding frequency of 36.5%, 39.2% and 24.3%, respectively. After stratification, the relative mean AUCs of omeprazole in EMs, SEMs and PMs were 1 : 2.7 : 9.3 (all p < 0.001). Accordingly, the CL/F of omeprazole showed a ratio of 9.8 : 3.6 : 1 for three phenotype groups, respectively. For other pharmacokinetic parameters including Cmax, t1/2, AUC normalised for bodyweight (AUCN), Cmax/dose and AUC/dose, there were also significant differences between the three groups.

CONCLUSIONS

The current pharmacokinetic study revealed that the majority of the Jordanian Arabics seemed to be more properly classified within the EM phenotype. More specifically, the observed metabolic rates of heterozygous and homozygous Jordanian Arabic EMs were more comparable to those of Caucasian EMs than Oriental EMs. Consequently, higher dosage requirements can be expected among most of the Jordanian Arabics. Yet, the incidence of PMs is significant and they seemed to exhibit a similar pharmacokinetic pattern to Chinese PMs in terms of long-term exposure (clearance and AUC) as well as short-term exposure (Cmax) parameters, after adjustment for dose and bodyweight. Therefore, further clinical application of CYP2C19 polymorphism is anticipated in Jordanian Arabic mixed population, particularly if long-term use of omeprazole is intended.

A pharmacokinetic interaction study between omeprazole and the H2-receptor antagonist ranitidine

The effect of ranitidine pretreatment on the pharmacokinetics of omeprazole was investigated in 14 male human volunteers. Omeprazole (40 mg, gastroresistant pellets) was administered to the volunteers in a two-treatment study design, either alone or after 5 days pretreatment with b.i.d. doses of 150 mg ranitidine. Plasma concentrations of omeprazole were determined over a 24-hour period following drug administration, by a validated RP-HPLC method. Pharmacokinetic parameters were calculated with compartmental and non-compartmental analysis, using the computer program Kinetica (Inna Phase). In the two periods of treatments, the mean peak plasma concentrations Cmax were 730.8 ng/ml for omeprazole alone and 802.1 ng/ml for omeprazole co-administered with ranitidine (not significant). The time taken to reach the peak, Tmax, was 1.29 h and 1.42 h, respectively (not significant). The areas under the curve (AUC0-10) were 1,453.3 ng.h/ml and 1,736.8 ng.h/ml for the two periods of treatment; thus a greater AUC was obtained after pretreatment with multiple doses of ranitidine. Our data show that the pharmacokinetics of omeprazole might be inhibited by pretreatment with ranitidine; however, the clinical relevance of this interaction still has to be confirmed.

Effectiveness of omeprazole- versus lansoprazole-based triple therapy for Helicobacter pylori eradication

Triple therapy with a proton pump inhibitor (PPI), amoxicillin, and clarithromycin is widely accepted for Helicobacter pylori eradication. The choice of PPI for triple therapy in Israel is arbitrary, with no preference for any one PPI except for economic considerations. Direct comparison between omeprazole and lansoprazole for efficacy of H. pylori eradication has never been performed in an Israeli poplulation. Based on the pharmacokinetic data, lansoprazole-based therapy may be a better alternative than omeprazole-based therapy. The aim of this study was to compare the effectiveness of triple therapy regimens with omeprazole (Losec, AstraZeneca; or Omeradex, Dexxon) or lansoprazole (TAP Pharmaceuticals) in eradicating H. pylori infection. The database of the biggest health insurance provider in Israel was reviewed for all patients who received 1 week of treatment with omeprazole (n = 1293) or lansoprazole (n = 85) with additional amoxicillin and clarithromycin for H. pylori eradication in 2002. All patients underwent the 13C-urea breath test (13CUBT) for validation of eradication. A negative 13CUBT result was noted in 1026 of the patients treated with omeprazole (79.4%) and 61 treated with lansoprazole (71.8%). On logistic regression analysis, none of the confounding factors (sex, age, indication, chronic use of PPI, eradication protocol) were found to contribute to the discrimination between a negative (successful eradication) and a positive (failed eradication) 13CUBT. There is no statistically significant difference between omeprazole and lansoprazole as part of a PPI-based triple therapy for eradication of H. pylori.

Review article: relationship between the metabolism and efficacy of proton pump inhibitors--focus on rabeprazole

Proton pump inhibitors are now considered the mainstay of treatment for acid-related disease. Although all proton pump inhibitors are highly effective, the antisecretory effects of different drugs in this class are not completely consistent across patients. One reason for this is the acid-suppressing effect of Helicobacter pylori infection, which may augment the actions of proton pump inhibitors. A second important reason for interpatient variability of the effects of proton pump inhibitors on acid secretion involves genetically determined differences in the metabolism of these drugs. This article focuses on the impact of genetic polymorphism of cytochrome P450 (CYP)2C19 on the pharmacokinetics and pharmacodynamics of proton pump inhibitors, particularly rabeprazole. Results reviewed indicate that the metabolism and pharmacokinetics of rabeprazole differ significantly from those of other proton pump inhibitors. Most importantly, the clearance of rabeprazole is largely nonenzymatic and less dependent on CYP2C19 than other drugs in its class. This results in greater consistency of pharmacokinetics for rabeprazole across a wide range of patients with acid-related disease, particularly those with different CYP2C19 genotypes. The pharmacodynamic profile for rabeprazole is also characterized by more rapid suppression of gastric acid secretion than with other proton pump inhibitors, which is also independent of CYP2C19 genotype. The favourable pharmacokinetic/pharmacodynamic profile for rabeprazole has been shown to result in high eradication rates for H. pylori in both normal and poor metabolizers. Pharmacodynamic results have also suggested that rabeprazole may be better suited than omeprazole as on-demand therapy for symptomatic gastro-oesophageal reflux disease. Finally, the use of rabeprazole is not complicated by clinically significant drug-drug interactions of the type that have been reported for omeprazole.

Efficacy of Sildenafil Citrate at 12 Hours after Dosing: Re-exploring the Therapeutic Window

OBJECTIVE

This open-label study investigated the efficacy of sildenafil citrate at 12 hours postdose among prior treatment responders.

PATIENTS AND METHODS

Eight 100-mg doses of sildenafil were provided to 40 eligible patients with erectile dysfunction (ED), who were to record the results of each sexual attempt in a patient diary. Each patient was instructed to make a sexual attempt at 1 and 12 hours postdose on 4 occasions (part 1) and only at 12 hours postdose on 4 subsequent occasions (part 2).

RESULTS

Of 40 enrolled patients, 34 (85%) completed the study. In these evaluable patients, 97% and 74% of patients achieved erections that resulted in successful intercourse at 1 hour and 12 hours postdose, respectively. There was a nonsignificant reduction in the percentage of responders at 12 hours during part 1 versus part 2 of this study (71% versus 78%).

CONCLUSIONS

This study demonstrates that, in the majority of these patients with ED, sildenafil remains clinically active 12 hours after administration. Larger studies may be necessary to confirm and clarify the therapeutic window of sildenafil.

GERD 2004: issues from the past and a consensus for the future

In the early 1900's, gastroesophageal reflux disease (GERD) was an almost unknown entity with less than 200 cases reported worldwide. Currently the disease is regarded as almost endemic with as much as 25% of the population in some countries exhibiting signs or symptoms of reflux. Early therapies directed at chemical neutralization (milk drip, antacids) were of modest effect and required constant administration for efficacy. The introduction of histamine 2 receptor antagonists in the 1970's dramatically improved the management of GERD, but was limited by problems of tachyphylaxis and adverse events. The advent of the PPI class of drugs revolutionized medical care of GERD, given their efficacy and safety profile. As a consequence, the surgical approach with its pronounced dependence on individual operator skill and its high morbidity and even mortality has fallen into disregard. Thus, modest surgical outcome results as compared to the efficacy of PPIs has led to the widespread recognition that pharmacological therapy for GERD represents the platinum standard of care and the current consensus is that the PPI class of drugs provide the safest and most effective form of therapy for GERD. Furthermore, it is apparent based on acid suppression, symptom relief and healing rates, that all PPIs are on a milligram for milligram basis similarly efficacious for the management of GERD. While a consensus exists in regard to the current management of GERD with PPIs there is little agreement as to the management of the associated mucosal metaplastic process. At this time there is inadequate understanding of the biological basis of the mucosal transformation and minimal information about the mechanistic regulation of this event and its perpetuation. A future consensus thus requires the identification of the appropriate tools to detect Barrett's early, identify the specific molecular markers associated with neoplastic transformation and establish a definitive therapeutic algorithm.

GERD 2003 -- a consensus on the way ahead

Gastroesophageal reflux disease (GERD) has in recent times become an important public health issue owing to the considerable health care resources utilized in its management, its deleterious effect on quality of life and the increasing prevalence of a relatively rare complication of reflux disease - esophageal adenocarcinoma. We review here the major current challenges in the field of reflux disease and its complications, and provide some approaches that may be useful in management. The issues to be faced include the very limited comprehension of the reasons behind the increasing prevalence of the disease, difficulties in correlating symptoms with objective data of pathological gastroesophageal reflux and the relatively unsophisticated tools we are employing to investigate the underlying pathophysiology. It is certain that the lack of well-defined and characterized methodologies to compare the effects of therapy require the development of more effective questionnaire-type analytic tools. In regard to treatment, there is little doubt that the widely prescribed proton pump inhibitors have dose-equivalent efficacy and are the most highly effective agents capable of suppressing acid, controlling many of the symptoms of GERD and healing erosions. Nevertheless, many patients continue to experience symptoms on withdrawal or at night. Pharmacological agents that can effectively increase lower esophageal sphincter pressure or promote motility are as yet unavailable. Although the introduction of laparoscopic techniques has resulted in a modest revival in surgical intervention using a variety of 'wrap-type' operations, the indications are few and the procedure is associated with a significant morbidity and even mortality especially if the expertise of the surgeon is an issue. Endoscopic techniques of regulating reflux are at this time experimental and not applicable to the general population. Intestinal metaplasia in the lower esophagus is probably very common. Whether and how to, first, screen for, and then, perform surveillance in Barrett's esophagus remains highly problematic and contentious.

Bioequivalence and other unresolved issues in generic drug substitution

BACKGROUND

Substitution of generic drugs for brand-name products is highly controversial and often is met with suspicion by health care providers and patients. Historically, the debate has focused on the issue of bioequivalence, and clinical practice has identified a number of drug classes for which generic substitution should be approached with caution. Current bioequivalence requirements are based on a measure of average bioequivalence; however, there are fears that use of this measure may be inappropriate in the case of a drug with a narrow or wide therapeutic range or high intrasubject or intersubject variability. Under these circumstances, measures of individual and population bioequivalence are proposed to be more accurate than measures of average bioequivalence.

OBJECTIVE

This paper addresses issues of bioequivalence and other concerns with generic drug substitution.

METHODS

I conducted a MEDLINE search of the English-language literature containing the key terms generic, multisource, quality, and brand and published between 1973 and 2003. The names of branded pharmaceuticals whose patents had recently expired (eg, Ventolin HFA, Adalat, Capoten, Tagamet HB 200, and Valium) also were used to search for articles on generic substitution. Reference lists of relevant articles also were searched. Bioequivalence issues are presented together with more general concerns over generic drug substitution, such as consumer perception of risk, differences in product and packaging appearance, and differences in excipients.

RESULTS

The literature reviewed act to highlight a number of different drug categories and patient subpopulations for which generic substitution can still prove to be problematic.

CONCLUSION

I recommend that health care providers continue to exercise caution in the consideration of generic drug substitution under certain circumstances.