Pharmacokinetic considerations in the eradication of Helicobacter pylori

Comparison of Amoxicillin Administered Twice versus Four Times a Day in First-Line Helicobacter pylori Eradication Using Tegoprazan, Clarithromycin, and Bismuth: A Propensity Score Matching Analysis

This study aimed to investigate the effects of different amoxicillin (AMX) dosing schedules on bismuth quadruple therapy in Helicobacter pylori treatment-naïve patients. A total of 139 H. pylori-infected patients received a 2-week eradication regimen consisting of 50 mg tegoprazan, 500 mg clarithromycin, and 300 mg bismuth tripotassium dicitrate twice daily, 1000 mg AMX twice daily (BID group), or 500 mg AMX four times daily (QID group). We performed a urea breath test to evaluate H. pylori eradication eight weeks after treatment and compared the H. pylori eradication rate, patient compliance, and adverse drug events between the BID and QID groups. Based on propensity score matching, 114 and 100 patients were included in intention-to-treat (ITT) and per-protocol (PP) analyses, respectively. The H. pylori eradication rate did not differ significantly according to the ITT (82.5% vs. 87.7%, p = 0.429) and PP (95.9% vs. 98.0%, p = 0.536) analyses between the BID and QID groups. No significant differences were found in treatment compliance or adverse drug event rates between the two groups. In conclusion, the eradication rate of first-line H. pylori therapy containing tegoprazan, clarithromycin, and bismuth was not affected by AMX dosing schedules administered twice and four times daily.

Evaluating physicians' awareness and prescribing trends regarding proton pump inhibitors: a cross-sectional study

Introduction: Proton pump inhibitors (PPIs) are commonly used to treat acid-related disorders. Their appropriate use depends on the correct indications from the clinician. Owing to the high incidence of use and misuse, PPIs have been identified as an essential pharmacological class for developing deprescribing recommendations. Therefore, assessing physicians' knowledge and practice regarding PPI usage is critical for paving the way toward targeted recommendations and efforts. Objective: This study aimed to assess Syrian physicians' perceptions of proton pump inhibitors adverse effects, their benefit in upper gastrointestinal bleeding (UGIB) prophylaxis, and how these perceptions are related to PPI prescription practice. Methods: A cross-sectional study was performed using a web-based questionnaire distributed among Syrian physicians in internal medicine between 28 November and 23 December 2022. The questionnaire assessed perceptions and experiences of PPIs, concerns about specific adverse effects, and their effectiveness for UGIB prophylaxis, in addition to the different scenarios used to determine the best practice for appropriate treatment to manage minimal, mild, moderate, and high-risk UGIB patients. Results: A total of 473 participants completed the questionnaire, with median age ±SD was (28.46 ± 4.58), and most participants (83.3%) were residents. Approximately half of the participants (45.5%) agreed that discussion assistance was provided to continue or terminate PPIs properly. Only 8.9% were very familiar with published evidence of PPI adverse effects. Bone weakening and vitamin B12 deficiency were the most frequently reported side effects (81.8% and 79.7%, respectively). However, dementia (0.4%) and mortality (1.9%) were the least reported adverse effects. More than half of the participants (64%) perceived using PPIs to prevent upper GI bleeding. Non-trainee physicians were less knowledgeable about appropriate GERD management than resident physicians (p < 0.001). Conclusion: The study showed a gap between Syrian physicians' perceptions and practices regarding PPI use, which necessitates spreading awareness of updated guidelines for PPI usage and their side effects.

Pharmacokinetics, Safety, and Tolerability of Vonoprazan- or Esomeprazole-Based Bismuth-Containing Quadruple Therapy: A Phase 1, Double-Blind, Parallel-Group Study in Adults with Helicobacter pylori Infection in China

Quadruple therapy comprising 2 antibiotics, a proton pump inhibitor, and bismuth, is recommended for Helicobacter pylori eradication in China. This Phase 1, double-blind, parallel-group study aimed to evaluate the pharmacokinetics, safety, and tolerability of bismuth-containing vonoprazan- or esomeprazole-based quadruple therapy in H. pylori-positive healthy subjects at a single site in China. Quadruple therapy comprising vonoprazan 20 mg or esomeprazole 20 mg with bismuth potassium citrate 600 mg (equivalent to bismuth 220 mg), clarithromycin 500 mg, and amoxicillin 1000 mg was administered twice daily for 2 weeks. Forty-four subjects were enrolled, 22 each in the vonoprazan (mean age, 34.5 years; men, 63.6%) and esomeprazole (mean age, 31.6 years; men, 59.1%) groups. Day 14 bismuth plasma pharmacokinetic parameters area under the plasma concentration-time curve during a dosing interval (geometric mean ratio, 1.07 [90% confidence interval, 0.82-1.40]) and maximum observed plasma concentration (geometric mean ratio, 1.30 [90% confidence interval, 0.94-1.81]) were similar between the treatment groups. At Day 42 follow-up, 100% and 94.4% of subjects were H. pylori negative in the vonoprazan and esomeprazole groups, respectively. The incidence of treatment-emergent adverse events was similar between the groups, with no serious adverse events. No new safety concerns were identified. In conclusion, vonoprazan had no significant effect on plasma bismuth exposure compared with esomeprazole.

A Modified 14-Day Dual Therapy with Vonoprazan and Amoxicillin Amplified the Advantages Over Conventional Therapies for Eradication of Helicobacter pylori: A Non-Inferiority Clinical Trial

Purpose

The emergence of resistant strains has greatly reduced the eradication rate of H. pylori (HP) in conventional bismuth-containing quadruple therapy. Meanwhile, the new 7-day dual therapy with vonoprazan (VPZ) and amoxicillin (AMO) failed to achieve the expected therapeutic effect in China.

Patients and Methods

A total of 256 untreated HP-infected patients are included in this non-inferiority clinical trial. The patients were randomly divided into three groups: 14-day dual therapy group (VPZ 20mg b.i.d + AMO 750mg t.i.d for 14 days, VA14), 14-day modified triple therapy group (VA14 + Jinghua Weikang Capsule 160mg t.i.d, VAC), and conventional bismuth-containing quadruple therapy group for 14 days (BCQ). Eradication rates, drug-related adverse events (AEs), patient compliance, and drug costs were compared among the three groups.

Results

The eradication rates in the BCQ, VA14, and VAC were 78.67, 77.33%, and 86.49% by intention-to-treat analysis, respectively, and 96.72%, 90.63%, and 92.75% by pre-protocol or modified intention-to-treat analysis, respectively. VA14 therapy indicated a non-inferiority eradication rate and advanced safety and economics to BCQ therapy. JWC further improved the eradication rate and reduced the incidence of AEs.

Conclusion

A modified 14-day dual therapy with VPZ and AMO provides satisfied efficacy as the first-line treatment for HP infection in China.

Proton pump inhibitor-induced gut dysbiosis and immunomodulation: current knowledge and potential restoration by probiotics

Proton pump inhibitors (PPIs) are the most commonly prescribed drugs for the treatment of non-erosive reflux disease (NERD), ulcers associated with non-steroidal anti-inflammatory drugs (NSAIDs), esophagitis, peptic ulcer disease (PUD), Zollinger-Ellison syndrome (ZES), gastroesophageal reflux disease (GERD), non-ulcer dyspepsia, and Helicobacter pylori eradication therapy. The drugs have the effect of inhibiting acid production in the stomach. According to research, PPIs can affect the composition of gut microbiota and modulate the immune response. Recently, there has been a problem with the over-prescription of such drugs. Although PPIs do not have many side effects, their long-term use can contribute to small intestinal bacterial overgrowth (SIBO) or C. difficile and other intestinal infections. Probiotic supplementation during PPIs therapy may provide some hope in the reduction of emerging therapy side effects. This review aims to present the most important effects of long-term PPI use and provides critical insights into the role of probiotic intervention in PPI therapy.

Vonoprazan and high-dose amoxicillin dual therapy for Helicobacter pylori first-line eradication: A single-arm, interventional study

Background

To date, no interventional trial has assessed the efficacy and safety of vonoprazan and high-dose (500 mg four times daily, 2000 mg/day) amoxicillin dual therapy in terms of Helicobacter pylori eradication. We explored whether this was an appropriate first-line treatment.

Methods

This prospective, dual-center, single-arm interventional study was performed in Japan. Twenty H. pylori-positive patients lacking any eradication history were treated with vonoprazan 20 mg twice daily and amoxicillin 500 mg four times daily (qid) for 7 days. Eradication was evaluated using a stool H. pylori antigen test. We evaluated safety using patient questionnaires. This study was registered in the jRCT database (jRCT031200128).

Results

The intention-to-treat and per-protocol eradication rates were 90% (95% confidence interval [CI] 68.3-98.8%, n = 20) and 94.4% (95% CI 72.7-99.9%, n = 18) respectively. No significant adverse event was recorded.

Conclusion

Vonoprazan/high-dose amoxicillin dual therapy can be a safe standard first-line therapy. We are now undergoing a randomized controlled trial comparing dual therapy and vonoprazan-based triple therapy.

Evaluation of pharmacokinetic interactions of amoxicillin with ranitidine in healthy human volunteers of Karachi, Pakistan

Polypharmacy may be considered as the customary practice to provide optimum care services to patients but inter resulted in augmented probability of multiple drug interaction. Keeping in view the importance of drug interaction possibility, this study was designed to evaluate the effect of ranitidine on pharmacokinetics of amoxicillin in the local population of Karachi, Pakistan. Amoxicillin and ranitidine are the most commonly prescribed drugs to treat duodenal ulcer caused by Helicobacter pylori. The current investigation was carried out as a single center, open label, two phase, single dose, randomized way in cross over manner to evaluate the potential of pharmacokinetic interaction among amoxicillin formulation and ranitidine in adult healthy male volunteers. Post dosing blood samples were collected at multiple time points that are 0.5, 1, 1.5, 2, 3, 4, 6, 8 and 10 hours after administering amoxicillin 250mg capsule with and without ranitidine. For estimation of amoxicillin concentration in plasma, an HPLC method was developed and validated. The solvent system consisted of 0.025M phosphate buffer: acetonitrile (94:6 v/v). C18 column was employed with a flow rate of 1.0 ml/minute and at 230nm. A linear pattern with a correlation coefficient of 0.999 in the concentration ranges of 25μg/mL to 0.097μg/mL for amoxicillin and 25μg/mL to 0.048μg/mL for ranitidine was observed. Amoxicillin retention time was about 8 minutes and ranitidine retention time was around 12 minutes. Amoxicillin levels were computed and the concentrations were applied to calculate the pharmacokinetic parameters. Pharmacokinetic parameters were estimated by Kinetica TM 4.4.1 (Thermo Electron Corp. USA). The analysis of variance (two way) and t test (two one sided) were applied on log transformed pharmacokinetic parameters of amoxicillin. The T_max was determined between amoxicillin alone and amoxicillin with ranitidine by Friedman test. The 90% confidence interval values for C_max(calc) (0.687–0.743) and T_max(calc) (1.148–1.742) for amoxicillin with or without ranitidine were not found within the FDA acceptable limits of 0.8–1.25. Study demonstrated the significant reduction in peak plasma levels of amoxicillin in presence of ranitidine. It is advisable to administer both drugs with time interval to avoid such interactions and increases in the bactericidal efficacy of amoxicillin.

Evaluation of safety and pharmacokinetics of bismuth-containing quadruple therapy with either vonoprazan or lansoprazole for Helicobacter pylori eradication

Aims

Helicobacter pylori (Hp) eradication plays a key role in the treatment and prevention of peptic ulcer diseases. Increasing clarithromycin resistance in Hp necessitates more effective treatments for eradication, such as bismuth‐containing quadruple therapy. We aimed to compare the safety and pharmacokinetics (PK) of bismuth between vonoprazan‐ and lansoprazole‐containing quadruple therapy in Hp‐positive subjects.

Methods

In this randomised, double‐blind, parallel‐group study, Hp‐positive subjects were randomised to receive vonoprazan‐ or lansoprazole‐containing quadruple therapy. Each subject received vonoprazan 20 mg or lansoprazole 30 mg combined with bismuth 220 mg, clarithromycin 500 mg and amoxicillin 1000 mg twice daily for 14 days. Blood sampling and urine collection for bismuth PK were conducted predose and up to 12 hours postdose at steady‐state. The PK parameters of bismuth were derived using a noncompartmental method and compared between treatments. An exploratory breath test for Hp was conducted at screening and at the follow‐up visit on day 42. Safety was assessed by adverse event monitoring, physical examinations, vital signs, 12‐lead electrocardiograms and clinical laboratory tests.

Results

A total of 30 subjects were randomised and 26 subjects completed the study (12 in the vonoprazan group and 14 in the lansoprazole group). The systemic exposure of bismuth in the 2 treatments was comparable (~5% difference). All subjects turned negative for Hp at the follow‐up visit. No significant difference in safety profiles was noted between the 2 treatments.

Conclusion

The systemic exposure of bismuth was similar between vonoprazan‐ and lansoprazole‐containing quadruple therapy. Vonoprazan‐containing quadruple therapy was safe and well tolerated.

Pharmacokinetics, Bioequivalence, and Safety Studies of Pantoprazole Sodium Enteric-Coated Tablets in Healthy Subjects

This study aimed to evaluate the bioequivalence of 2 pantoprazole sodium enteric-coated tablet formulations, a generic formulation and a branded formulation, and to investigate their pharmacokinetic and safety profiles. The study was designed as a single-center, randomized, open-label, single-dose, dual-period, and 2-sequence crossover trial, and was divided into fasting and postprandial human bioequivalence trials. In the first trial, 36 subjects were fasted overnight before they were given generic or branded tablets (during 2 separate administration periods). Separately, 42 subjects were provided a high-fat meal 1 hour before the drugs were administered. Blood specimens of each subject were obtained up to 24 hours after drug administration. No significant differences were observed between the pharmacokinetic profiles of the generic and branded pantoprazole sodium enteric-coated tablets. Bioequivalence was evaluated using 90% confidence intervals for the ratio of test/reference log area under the concentration-time curve over 24 hours, log area under the concentration-time curve to infinity (AUC_0-∞ ), and log peak concentration (C_max ). The 90% confidence intervals of the least squares geometric mean ratio of C_max , area under the concentration-time curve from time zero to the last measurable concentration (AUC_0-t ), and AUC_0-∞ of 36 subjects in the fasting trial and of 40 of 41 subjects in the postprandial trial (C_max [41], AUC_0-t [41], and AUC_0-∞ [40]) were in accordance with the bioequivalence criteria. No severe adverse effects were detected. The generic and branded pantoprazole sodium enteric-coated tablets were considered bioequivalent with similar safety profiles.

Efficacy of Reduced Dosage of Amoxicillin in an Eradication Therapy for Helicobacter pylori Infection in Patients on Hemodialysis: A Randomized Controlled Trial

BACKGROUND

An optimum Helicobacter pylori-eradication regimen for hemodialysis patients is yet to be established because of different pharmacokinetics of amoxicillin involved between hemodialysis patients and healthy subjects. We investigated to establish appropriate doses of amoxicillin for H. pylori infection eradication in hemodialysis patients.

METHODS

Of 409 hemodialysis patients screened for H. pylori infection, 37 H. pylori-positive patients were randomized to different 1-week eradication regimens: esomeprazole 20 mg twice a day (b.i.d.) and clarithromycin 200 mg b.i.d., plus amoxicillin at either 750 mg b.i.d. (group A; conventional) or 250 mg b.i.d. (group B; experimental). Sixty-three patients with normal renal function received the conventional regimen (group C). Successful eradication was confirmed by urea breath testing.

RESULTS

Eradication rates of group B (reduced amoxicillin-regimen) were 84.2% in intention-to-treat analysis and 88.9% in per-protocol analysis, which were similar with group A (77.8 and 77.8%) and group C (74.6 and 81.0%). However, the incidence of adverse events in group A was significantly higher than that in group C (22.2 vs. 5.1%, p = 0.027).

CONCLUSIONS

In H. pylori-positive hemodialysis patients, amoxicillin at 250 mg b.i.d. may be an appropriate scheme for eradication with equivalent effects to the conventional therapy and safety effects for adverse events.

Mass balance and metabolism of Z-215, a novel proton pump inhibitor, in healthy volunteers

The human mass balance of [¹⁴C]Z-215, a novel proton pump inhibitor, was characterised in six healthy male volunteers following single oral administration of [¹⁴C]Z-215 (20 mg, 3.7 MBq) to determine the elimination pathway of Z-215 and the distribution of its metabolites in plasma, urine, and faeces (NCT02618629). [¹⁴C]Z-215 was rapidly absorbed, with a C_max of 434 ng/mL at 0.38 h for Z-215 and 732 ng eq./mL at 0.5 h for total radioactivity. Means of 59.61% and 31.36% of the administered radioactive dose were excreted in urine and faeces, respectively, within 168 h post-dose. The majority of the dose was recovered within 24 h in urine and 96 h in faeces. Unchanged Z-215 was excreted in urine at trace levels but was not detected in faeces. The main components in plasma were Z-215 and Z-215 sulphone, accounting for 29.8% and 13.3% of the total circulating radioactivity, respectively. Additionally, Z-215 was metabolised through oxidation, reduction and conjugation. Our in vitro Z-215 metabolism study showed that the major isozyme contributing to the oxidation of Z-215, including the formation of Z-215 sulphone, was CYP3A4. In conclusion, Z-215 is well absorbed in humans and primarily eliminated via metabolism, where CYP3A4 plays an important role.

25 Years of Proton Pump Inhibitors: A Comprehensive Review

Proton pump inhibitors (PPIs) were clinically introduced more than 25 years ago and have since proven to be invaluable, safe, and effective agents for the management of a variety of acid-related disorders. Although all members in this class act in a similar fashion, inhibiting active parietal cell acid secretion, there are slight differences among PPIs relating to their pharmacokinetic properties, metabolism, and Food and Drug Administration (FDA)-approved clinical indications. Nevertheless, each is effective in managing gastroesophageal reflux disease and uncomplicated or complicated peptic ulcer disease. Despite their overall efficacy, PPIs do have some limitations related to their short plasma half-lives and requirement for meal-associated dosing, which can lead to breakthrough symptoms in some individuals, especially at night. Longer-acting PPIs and technology to prolong conventional PPI activity have been developed to specifically address these limitations and may improve clinical outcomes.

The effect of MDR1 C3435T polymorphism on the eradication rate of H. pylori infection in PPI-based triple therapy: A meta-analysis

BACKGROUND

Several studies have reported that multidrug resistance gene 1 (MDR1) C3435T polymorphism was associated with the rate of Helicobacter pylori (H. pylori) eradication in proton pump inhibitor (PPI)-based triple therapy. However, the conclusions were inconsistent. Therefore, this meta-analysis was conducted to evaluate the impact of MDR1 C3435T polymorphism on H. pylori eradication by PPI-based triple therapy.

METHODS

Seven eligible studies published up to August 2016 and including 1019 patients were identified by searching the Chinese Biomedical Literature database, Wan fang, PubMed, and the Web of Science electronic databases. Consequently, a meta-analysis was conducted with STATA software, using summary odds ratios (OR) and a 95% confidence interval (CI).

RESULTS

Overall, there was no significant difference between MDR1 C3435T polymorphism and the eradication rate of H. pylori in the entire genetic model, irrespective of the PPI used. Furthermore, in Asian populations, the TT genotype decreased H. pylori eradication (TT vs CT+CC: OR=0.411, 95% CI = 0.280-0.602, P = 0.000). In addition, a significantly low eradication rate was observed in a recessive model, in which either lansoprazole (TT vs CT+CC: OR = 0.305, 95% CI = 0.184-0.504, P = 0.000) or omeprazole (TT vs CT+CC: OR = 0.229, 95% CI = 0.069-0.763, P = 0.016) was taken, in a subanalysis of individual PPIs. In the analyses that were stratified by disease type, no significant difference was observed in the peptic ulcer group and the combined diseases subgroup.

CONCLUSION

This meta-analysis indicated that the TT genotype of the MDR1 C3435T polymorphism decreased H. pylori eradication in Asian populations and was also associated with a low cure rate of H. pylori in patients taking lansoprazole- and omeprazole-based triple therapies. However, future studies using larger sample sizes are required.

How May Proton Pump Inhibitors Impair Cardiovascular Health?

Proton pump inhibitors (PPIs) are among the most widely used drugs worldwide. They are used to treat a number of gastroesophageal disorders and are usually prescribed as a long-term medication or even taken without a prescription. There are a number of clinical studies that associate PPI use with an increased cardiovascular risk. In this article, we review the clinical evidence for adverse cardiovascular effects of PPIs, and we discuss possible biological mechanisms by which PPIs can impair cardiovascular health.

Proton pump inhibitors while belonging to the same family of generic drugs show different anti-tumor effect

CONTEXT

Tumor acidity represents a major cause of chemoresistance. Proton pump inhibitors (PPIs) can neutralize tumor acidity, sensitizing cancer cells to chemotherapy.

OBJECTIVE

To compare the anti-tumor efficacy of different PPIs in vitro and in vivo.

MATERIALS AND METHODS

In vitro experiments PPIs anti-tumor efficacy in terms of cell proliferation and cell death/apoptosis/necrosis evaluation were performed. In vivo PPIs efficacy experiments were carried out using melanoma xenograft model in SCID mice.

RESULTS

Lansoprazole showed higher anti-tumor effect when compared to the other PPIs. The lansoprazole effect lasted even upon drug removal from the cell culture medium and it was independent from the lipophilicity of the PPIs formulation.

DISCUSSION

These PPIs have shown different anti-tumoral efficacy, and the most effective at low dose was lansoprazole.

CONCLUSION

The possibility to contrast tumor acidity by off-label using PPIs opens a new field of oncology investigation.

Population pharmacokinetics of omeprazole in critically ill pediatric patients

BACKGROUND

To develop a population pharmacokinetic model for intravenous omeprazole in critically ill children.

METHODS

One hundred eighty-six omeprazole concentration-time data from 40 critically ill children were analyzed using the nonlinear mixed-effects approach with the nonlinear mixed-effects modeling software, version 7.2 software. Patients were randomized into 2 groups and received intravenous omeprazole at a dose of 0.5 or 1 mg/kg twice daily. Blood samples were drawn at 0.5, 2, 6, 12, 24, and 48 hours after the first infusion.

RESULTS

The pharmacokinetic profile was best described by a 2-compartment model with a first-order elimination process. Between-patient variability could only be associated with plasma clearance (CL). The typical values for plasma CL were 24.9 L·h·70 kg (10.08%), with a distributional clearance of 53.9 L·h·70 kg (11.00%) and central and peripheral compartment distribution volumes of 4.23 L/70 kg (19.62%) and 674 L/70 kg (0.89%), respectively. Allometric size models seemed to predict changes adequately in all the pharmacokinetic parameters. High values of between-patient variability of CL [75.50% (2.60%)] and residual variability [130.0% (5.26%)] were still found in the final model. Model-based simulations suggested that the most suitable dose was 1 mg/kg because this yielded similar exposure (defined by the area under the concentration-time curve) to that obtained in adults after a 20-mg dose of omeprazole intravenously.

CONCLUSIONS

An allometric size model allows changes to be predicted in all the pharmacokinetic parameters, making dose adjustment by body weight important to achieve the most effective omeprazole exposure. This is the first step toward a population pharmacokinetic study, including more data to develop a predictable model to be used during therapeutic drug monitoring.

Prediction of inter-individual variability in the pharmacokinetics of CYP2C19 substrates in humans

Significant inter-individual variability of exposure for CYP2C19 substrates may be only partly due to genetic polymorphism. Therefore, the in vivo inter-individual variability in hepatic intrinsic clearance (CL(int,h)) of CYP2C19 substrates was estimated from reported AUC values using Monte Carlo simulations. The coefficient of variation (CV) for CL(int,h) in poor metabolizers (PM) expected from genotypes CYP2C19*2/*2, CYP2C19*3/*3 or CYP2C19*2/*3 was estimated as 25.8% from the CV for AUC of omeprazole in PMs. With this, CVs of CL(int,h) in extensive metabolizers (EM: CYP2C19*1/*1), intermediate metabolizers (IM: CYP2C19*1/*2 or *3) and ultra-rapid metabolizers (UM), CYP2C19*17/*17 and *1/*17, were estimated as 66.0%, 55.8%, 6.8% and 48.0%, respectively. To validate these CVs, variability in the AUC of CYP2C19 substrates lansoprazole and rabeprazole, partially metabolized by CYP3A4 in EMs and IMs, were simulated using the CV in CL(int,h) for CYP2C19 EMs and IMs and 33% of the CV previously reported for CYP3A4. Published values were within 2.5-97.5 percentile range of simulated CVs for the AUC. Furthermore, simulated CVs for the AUC of omeprazole and lansoprazole in ungenotyped populations were comparable with published values. Thus, estimated CL(int,h) variability can predict variability in the AUC of drugs metabolized not only by CYP2C19 but also by multiple enzymes.

Effect of dosing schemes of amoxicillin on eradication rates of Helicobacter pylori with amoxicillin-based triple therapy

OBJECTIVES

In standard regimens for Helicobacter pylori infection, amoxicillin is dosed twice daily, although the bactericidal effect of amoxicillin depends on the %time-above-MIC. We aimed to examine whether dosing schemes of amoxicillin influenced eradication rates of amoxicillin-based regimens.

METHODS

One hundred eighty-seven patients infected with clarithromycin-sensitive strains of H. pylori were treated with PPI, clarithromycin 200 mg bid and amoxicillin 750 mg bid, 500 mg tid or 500 mg qid for 1 week and 125 infected with clarithromycin-resistant strains were treated with PPI, metronidazole 250 mg bid and amoxicillin 750 mg bid, 500 mg tid or 500 mg qid for 1 week.

RESULTS

Eradication rates (ITT) of the triple PPI/amoxicillin/clarithromycin therapy with bid, tid and qid dosings of amoxicillin were 77.8% (49/63), 93.5% (58/62), and 91.9% (57/62), respectively. Those of the triple PPI/amoxicillin/metronidazole therapy were 80.5% (33/41), 90.5% (38/42), and 95.2% (40/42), respectively. Eradication rates in regimens with tid and qid dosing of amoxicillin were higher than those of regimens with the bid dosing of amoxicillin.

CONCLUSIONS

The dosing scheme of amoxicillin significantly influenced eradication rates of triple therapies. Although amoxicillin is empirically dosed twice daily, amoxicillin should be dosed at least three times daily in amoxicillin-based triple therapies.

Severe hypoglycemia from Helicobacter pylori triple-drug therapy and insulin detemir drug interaction

Two drugs commonly used in triple-drug therapy for treatment of a Helicobacter pylori infection, clarithromycin and omeprazole, have rarely been associated with hypoglycemia when given alone. No documented interactions between H. pylori treatment with clarithromycin, amoxicillin, and omeprazole and insulin detemir have been previously reported. This case report describes an 82-year-old man with drug-controlled type 2 diabetes who experienced severe hypoglycemia during treatment for a H. pylori infection in an outpatient setting. His diabetes treatment included 32 units of insulin detemir once/day at bedtime and insulin aspart, determined by carbohydrate intake, 3 times/day with meals. After 5 days of clarithromycin 500 mg twice/day, amoxicillin 500 mg twice/day, and omeprazole 20 mg twice/day for treatment of the H. pylori infection, the patient experienced hypoglycemia and self-discontinued clarithromycin. Insulin detemir was decreased to 15 units and hypoglycemia reoccurred. Insulin detemir was further decreased to 10 units without further symptoms of hypoglycemia for the remainder of the H. pylori treatment. Once treatment was completed, the patient was instructed to resume taking 32 units of insulin detemir once/day. His blood glucose concentration returned to a baseline value, and he denied experiencing further hypoglycemic episodes. Health care practitioners should be aware of this possible drug interaction and anticipate that insulin detemir dosage adjustments may be required during treatment of H. pylori infection to avoid significant adverse events.

Gastric acid, calcium absorption, and their impact on bone health

Calcium balance is essential for a multitude of physiological processes, ranging from cell signaling to maintenance of bone health. Adequate intestinal absorption of calcium is a major factor for maintaining systemic calcium homeostasis. Recent observations indicate that a reduction of gastric acidity may impair effective calcium uptake through the intestine. This article reviews the physiology of gastric acid secretion, intestinal calcium absorption, and their respective neuroendocrine regulation and explores the physiological basis of a potential link between these individual systems.

Levofloxacin/amoxicillin-based schemes vs quadruple therapy for Helicobacter pylori eradication in second-line

Worldwide prevalence of Helicobacter pylori (H. pylori) infection is approximately 50%, with the highest being in developing countries. We compared cure rates and tolerability (SE) of second-line anti-H. pylori levofloxacin/amoxicillin (LA)-based triple regimens vs standard quadruple therapy (QT). An English language literature search was performed up to October 2010. A meta-analysis was performed including randomized clinical trials comparing 7- or 10-d LA with 7-d QT. In total, 10 articles and four abstracts were identified. Overall eradication rate in LA was 76.5% (95% CI: 64.4%-97.6%). When only 7-d regimens were included, cure rate was 70.6% (95% CI: 40.2%-99.1%), whereas for 10-d combinations, cure rate was significantly higher (88.7%; 95% CI: 56.1%-109.9%; P < 0.05). Main eradication rate for QT was 67.4% (95% CI: 49.7%-67.9%). The 7-d LA and QT showed comparable efficacy [odds ratio (OR): 1.09; 95% CI: 0.63-1.87], whereas the 10-d LA regimen was significantly more effective than QT (OR: 5.05; 95% CI: 2.74-9.31; P < 0.001; I(2) = 75%). No differences were reported in QT eradication rates among Asian and European studies, whereas LA regimens were more effective in European populations (78.3% vs 67.7%; P = 0.05). Incidence of SE was lower in LA therapy than QT (OR: 0.39; 95% CI: 0.18-0.85; P = 0.02). A higher rate of side effects was reported in Asian patients who received QT. Our findings support the use of 10-d LA as a simple second-line treatment for H. pylori eradication with an excellent eradication rate and tolerability. The optimal second-line alternative scheme might differ among countries depending on quinolone resistance.

Variation in omeprazole pharmacokinetics in a random Iranian population: a pilot study

Omeprazole is metabolized in the liver mainly by the polymorphic CYP2C19 enzyme. Considerable ethnic differences have been reported in the pharmacokinetics of omeprazole. The present study was conducted to evaluate the pharmacokinetic parameters of omeprazole after a single oral administration to a random Iranian population. Thirty healthy male subjects, aged 24-31 years, weighing 60-98 kg completed the study. Plasma concentrations of omeprazole were measured over a 12 h period after administration of a single oral dose of 20 mg omeprazole. The pharmacokinetic parameters were calculated from the plasma concentration-time profiles. Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was used to quantify 5-hydroxyomeprazole. The mean area under the concentration-time curve (AUC) from time zero to infinity (AUC(∞) ) values of omeprazole and the corresponding coefficient of variation (CV%) was 987.3 ng h/ml (65%). In general, most subjects showed a normal distribution. Only one subject showed a very high AUC compared with the corresponding mean AUC level. This subject had the highest half-life and the lowest rate of elimination. The omeprazole metabolic ratio for this subject was 2.9, while for the others it was in the range 0.12-0.56. These results are consistent with previous literature that showed the existence of interindividual variability in omeprazole pharmacokinetics, even within a single ethnic group. Differences in the pharmacokinetics could be due to differences in the genetic make-up of subjects as found in their omeprazole metabolic ratios.

Suspected methotrexate toxicity from omeprazole: a case review of carboxypeptidase G2 use in a methotrexate-experienced patient with methotrexate toxicity and a review of the literature

We report a case of methotrexate toxicity potentially induced by a drug interaction between methotrexate and omeprazole in a 25-year-old man with osteosarcoma. The patient was placed on omeprazole after his first cycle of high-dose methotrexate for stress ulcer prophylaxis, and it was discontinued before the start of the first day of the patient's second round of high-dose methotrexate. The 24-hour methotrexate level was elevated and he continued to have sustained levels for 18 days. Side effects due to elevated serum methotrexate included seizures, mucositis, acute renal failure, and thrombocytopenia. Aggressive hydration, urinary alkalinization, and leucovorin were continued during the period of elevated methotrexate levels, with the patient receiving a course of hemodialysis and a dose of carboxypeptidase G2. The patient's symptoms resolved, and his renal function returned to baseline within 2 months. The patient was able to receive future courses of chemotherapy without methotrexate. Although use of the Naranjo adverse reaction probability scale indicated a probable relationship (score of 6) between the patient's development of methotrexate toxicity and omeprazole use, we believe this was a drug-drug interaction case consistent with previous reports in the literature.

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.

Selective inactivation of a human neuronal silencing phosphatase by a small molecule inhibitor

The unstructured C-terminal domain (CTD) of eukaryotic RNA polymerase II dynamically regulates the process of transcription by recruiting different factors to nascent mRNA through its multiple phosphorylation patterns. A newly discovered class of phosphatases, the human small C-terminal domain phosphatases (Scp's), specifically dephosphorylates phosphorylated Ser(5) (phospho.Ser5) of the tandem heptad repeats of the CTD of RNA polymerase II. Scp's also function as transcription regulators that epigenetically silence the expression of specific neuronal genes, whose inactivation leads to neuronal stem cell differentiation. Small molecule inhibitors of Scp's will be valuable for elucidating their mechanism in nervous system development and can possibly offer new strategies to treat diseases related to neurodegeneration. Despite the difficulty in developing selective inhibitors of protein phosphatases, we have recognized a characteristic hydrophobic binding pocket adjacent to the active site in Scp's that may facilitate selective inhibition. In the present study, we successfully identified the first selective lead compound, rabeprazole, for the Scp/TFIIF-interacting CTD phosphatase (Fcp) family. The high-resolution crystal structure of rabeprazole-bound Scp1 showed that the compound indeed binds to the hydrophobic binding pocket. We further confirmed that rabeprazole only targets Scp's but not its close family members Fcp1 and Dullard or bacteriophage λ Ser/Thr phosphatase. Such specificity may prove important for In Vivo studies since accidental inhibition of Fcp1 or Dullard would result in cell malfunctions and even cell death.

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.

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.

Helicobacter pylori eradication with a 7-day low-dose triple therapy in hemodialysis patients

BACKGROUND

The optimal therapeutic regimen for Helicobacter pylori (H. pylori) infection has not been established in end-stage renal disease (ESRD) patients receiving hemodialysis. We investigated the efficacy and safety of a 7-day omeprazole-based triple therapy with low doses of amoxicillin and clarithromycin (OAC) for eradication of H. pylori infection in ESRD patients receiving hemodialysis.

METHODS

Thirty-three hemodialysis patients and 55 patients with normal renal function underwent upper gastrointestinal endoscopy. For eradication of H. pylori infection, a 7-day triple therapy with low-dose OAC (omeprazole 40 mg daily, amoxicillin 500 mg daily, and clarithromycin 500 mg daily) regimen was used. Four weeks after the completion of the OAC regimen, the success of the H. pylori eradication therapy was determined by histological examination and rapid urease test.

RESULTS

The prevalence of H. pylori infection was 36.4% in hemodialysis patients and 65.5% in non-uremic patients (p = 0.0150). The mean duration of hemodialysis in H. pylori-positive and -negative patients was 56.8 ± 26.9 versus 66.4 ± 26.1 months, respectively (p = 0.3196). Eradication was successful in 83.4% of hemodialysis patients and 81.0% of non-uremic patients (p = 1.000). All patients completed the eradication therapy without any serious adverse effects.

CONCLUSION

A 7-day triple therapy with a low-dose OAC regimen was effective and safe for eradication of H. pylori infection in hemodialysis patients.

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.

Methylated Metal(loid) Species in Humans

While the metal(loid)s arsenic, bismuth, and selenium (probably also tellurium) have been shown to be enzymatically methylated in the human body, this has not yet been demonstrated for antimony, cadmium, germanium, indium, lead, mercury, thallium, and tin, although the latter elements can be biomethylated in the environment. Methylated metal(loid)s exhibit increased mobility, thus leading to a more efficient metal(loid) transport within the body and, in particular, opening chances for passing membrane barriers (blood-brain barrier, placental barrier). As a consequence human health may be affected. In this review, relevant data from the literature are compiled, and are discussed with respect to the evaluation of assumed and proven health effects caused by alkylated metal(loid) species.

Pharmacokinetics of intravenous omeprazole in critically ill paediatric patients

The proton pump inhibitors are first-line drugs for the treatment of a number of gastrointestinal diseases. These drugs have a good safety profile, making it possible to use them in paediatric patients. Although their pharmacokinetics in children has not been extensively studied, research performed suggests that the dose used should be varied as a function of age, as this factor affects the drug's metabolism. Proton pump inhibitors can be used in critically ill children for the prophylaxis and treatment of gastrointestinal haemorrhage, although there is still little experience with this. The most widely used proton pump inhibitor at the present time is omeprazole. As there are specific characteristics of these patients that could alter the pharmacokinetics of the drugs, studies need to be performed to determine the most suitable dose and dosage interval.

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.

Efficient identification and evaluation of effective Helicobacter pylori therapies

Annually hundreds if not thousands of patients fail empiric H. pylori eradication therapy. Failure occurs in part because routine post treatment testing, which provides an early warning of increasing antibiotic resistance, is not universally done and physicians are generally unaware that cure rates with legacy triple therapy (a proton-pump inhibitor, amoxicillin, and clarithromycin) in most places has fallen below 80%. We propose first, institution of routine post eradication testing and second, abandonment of the "better than another therapy" approach to separating acceptable from unacceptable therapies. Instead, we propose using results-based outcomes (ie, >95% cure rates). H. pylori should be evaluated as other infectious diseases (ie, few would compare a new antibiotic for pneumonia with the previous best choice whose effectiveness was now impaired because of resistance). Randomized comparisons should be restricted to studies designed to improve (eg, simplify or reduce costs) high cure rate therapies while maintaining efficacy. We also discuss potential ethical issues such as those including known or suspected low cure rate therapies. Legacy therapies cannot be identified as "approved" or "recommended" even if both statements were true. Instead patients and ethics boards must receive "full disclosures" both before and during studies that include all that might affect a patient's decision to enter or to continue. Finally, we provides advice regarding trial design using "best shot" pilot studies to efficiently identify tentative effective regimens which are then confirmed in randomized trials all the while minimizing patient risks and drug exposure.

Determination of trimethylbismuth in the human body after ingestion of colloidal bismuth subcitrate

Biological methylation and hydride formation of metals and metalloids are ubiquitous environmental processes that can lead to the formation of chemical species with significantly increased mobility and toxicity. Whereas much is known about the interaction of metal(loid)s with microorganisms in environmental settings, little information has been gathered on respective processes inside the human body as yet. Here, we studied the biotransformation and excretion of bismuth after ingestion of colloidal bismuth subcitrate (215 mg of bismuth) to 20 male human volunteers. Bismuth absorption in the stomach and upper intestine was very low, as evidenced by the small quantity of bismuth eliminated via the renal route. Total bismuth concentrations in blood increased rapidly in the first hour after ingestion. Most of the ingested bismuth was excreted via feces during the study period. Trace levels of the metabolite trimethylbismuth [(CH(3))(3)Bi] were detected via low temperaturegas chromatography/inductively coupled plasma-mass spectrometry in blood samples and in exhaled air samples. Concentrations were in the range of up to 2.50 pg/ml (blood) and 0.8 to 458 ng/m(3) (exhaled air), with high interindividual variation being observed. Elimination routes of bismuth were exhaled air (up to 0.03 per thousand), urine (0.03-1.2%), and feces. The site of (CH(3))(3)Bi production could not be identified in the present study, but the intestinal microflora seems to be involved in this biotransformation if accompanying ex vivo studies are taken into consideration.

Helicobacter pylori eradication: role of individual therapy constituents and therapy duration

Treatment of Helicobacter pylori (H. pylori) infection has become a key factor in the management of dyspepsia and is the treatment of choice for peptic ulcer disease. First-line eradication regimens combining a proton pump inhibitor (PPI) with clarithromycin and amoxicillin or metronidazole are considered most effective when given for a minimum period of 1 week. Eradication regimens of shorter duration have shown promising results but clinical experience remains limited. Pharmacological properties such as bioavailability and plasma concentrations of individual PPIs differ between individuals but it remains unclear whether these differences impact on the efficacy of eradication therapy and are influenced by renal or hepatic impairment. Bioavailability of PPIs also differs and is impacted on by factors including intragastric pH, metabolic pathways, potency on an mg-for-mg basis and intrinsic antibacterial activity. Several significant pharmacokinetic differences between the PPIs do not seem to influence overall H. pylori eradication rates for first-line triple therapy. However, comparison of factors including pharmacokinetics and treatment duration may prove important in achieving successful eradication with second- and third-line treatments. Based on the factors which influence therapy outcome, we suggest an algorithm for the use of H. pylori eradication therapies.

Effects of CYP2C19 and MDR1 genotype on the eradication rate of Helicobacter pylori infection by triple therapy with pantoprazole, amoxycillin and clarithromycin

BACKGROUND

CYP2C19 polymorphism plays an important role in the metabolism of proton pump inhibitors. The multidrug resistance (MDR)1 genotype is associated with the successful eradication of Helicobacter pylori. The aim of the present study was to investigate the effects of CYP2C19 and MDR1 genotypes on the eradication rate of H. pylori using a pantoprazole-based triple therapy.

METHODS

A total of 210 patients infected with H. pylori were treated with 40 mg pantoprazole, 500 mg clarithromycin and 1000 mg amoxicillin twice daily for 7 days. The CYP2C19 genotype was determined with polymerase chain reaction (PCR)-restriction fragment length polymorphism analysis. The MDR1 C3435T polymorphism was identified by PCR-based allele-specific amplification (PCR-ASA).

RESULTS

Of the 210 patients who completed the study, 174 (82.9%, 95.0% confidence interval [CI], 77.8-88.0%) achieved successful eradication after the first cycle of therapy. The eradication rates for H. pylori were 86.7%, 81.1% and 82.1% in the homozygous extensive, heterozygous extensive and poor metabolizer groups, respectively (P = 0.65). Moreover, the cure rates in the CC, CT, and TT groups were 82.7%, 84.4% and 76.9%, respectively (P = 0.66). Multiple logistic regression analysis revealed that endoscopic diagnosis was a significant independent risk factor for treatment failure.

CONCLUSION

The eradication rates of H. pylori by pantoprazole, amoxicillin and clarithromycin were not significantly different among the CYP2C19 and MDR1 genotypes. Hence, the cure rate of H. pylori in the Korean population was no different for the CYP2C19 and MDR1 genotypes.

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.

Intragastric pH with oral vs intravenous bolus plus infusion proton-pump inhibitor therapy in patients with bleeding ulcers

BACKGROUND & AIMS

Intravenous bolus plus infusion proton pump inhibitor (PPI) therapy is recommended for patients with bleeding ulcers and higher risk stigmata. If frequent oral dosing of PPIs provided similar antisecretory effect, this might be preferred based on ease and cost.

METHODS

Patients presenting with overt bleeding due to ulcers had intragastric pH probes placed after endoscopy and baseline pH recorded. They were randomly assigned to intravenous lansoprazole (90-mg bolus followed by 9-mg/h infusion) or oral lansoprazole (120-mg bolus followed by 30 mg every 3 hours). pH was recorded for 24 hours.

RESULTS

Intragastric pH was > 6 for 67.8% of the study period with intravenous PPI (n = 32) and 64.8% with oral PPI (n = 34): difference, 3.0%; 95% confidence interval (CI): -9.2% to 15.2%. Intragastric pH was > 6 for > 60% of the study period in 22 (68.8%) patients receiving intravenous and 22 (64.7%) patients receiving oral PPI: difference, 4.0%; 95% CI: -18.7% to 26.8%. At 1 hour, mean pHs for intravenous vs oral were 5.3 +/- 0.4 vs 3.3 +/- 0.4, respectively (difference, 2.0; 95% CI: 0.8-3.1; P = .001). At > or = 1.5 hours, 95% CIs of the differences for all hourly mean pHs included zero. Mean pH rose above 6 after 2-3 hours of intravenous PPI and 3-4 hours of oral PPI.

CONCLUSIONS

Frequent oral PPI may be able to replace the currently recommended intravenous bolus plus infusion PPI therapy in patients with bleeding ulcers, although the possibility that intravenous PPIs are superior cannot be definitively excluded given our relatively wide confidence intervals. Intravenous PPI provides more rapid increase in pH, reaching mean pH of 6 approximately 1 hour sooner than oral PPI.

New concepts of resistance in the treatment of Helicobacter pylori infections

The prevalence of antimicrobial drug resistance is now so high that all patients infected with Helicobacter pylori should be considered as having resistant infections. Ideally, therapy should be based on pretreatment antibiotic-susceptibility testing but this strategy is not currently practical. At present, clarithromycin-containing triple therapies do not reliably produce a > or =80% cure rate on an intention-to-treat basis and are, therefore, no longer acceptable as empiric therapy. In this Review, we discuss concepts of resistance that have become part of mainstream thinking for other infectious diseases but have not yet become so with regard to H. pylori. We also put data on the pharmacokinetics and pharmacodynamics of the drugs used in H. pylori therapy and the effect of host cytochrome P450 genotypes in context with treatment outcomes. Our primary focus is to address the problem of H. pylori resistance from a novel perspective, which also attempts to anticipate the direction that research will need to take to provide clinicians with reliable approaches to this serious infection. We also discuss current therapies that provide acceptable cure rates when used empirically (i.e. sequential therapy; four-drug, three-antibiotic, non-bismuth-containing 'concomitant' therapy; and bismuth-containing quadruple therapy) and how they might be further improved.

Clinical efficacy of esomeprazole in the prevention and healing of gastrointestinal toxicity associated with NSAIDs in elderly patients

NSAIDs are widely prescribed for the treatment of pain, inflammation and rheumatic disorders, but their use is associated with adverse gastrointestinal effects, ranging from dyspeptic symptoms and peptic ulcers to more serious complications. Elderly patients are at high risk of experiencing NSAID-induced gastrointestinal tract injury and should be considered candidates for prophylactic pharmacological therapy. In studies conducted in adult patients, proton pump inhibitors (PPIs) such as esomeprazole have been shown to prevent or reduce NSAID-induced gastrointestinal injury. The beneficial effects of esomeprazole can be ascribed largely to its ability to maintain sustained inhibition of gastric acid secretion, although there is evidence to suggest that pharmacodynamic properties unrelated to acid inhibition may also contribute to the gastroprotective effects of this agent. Although there are limited data on the use of esomeprazole specifically in elderly patient populations, studies of patients at high risk of NSAID-induced gastrointestinal toxicity because of advanced age indicate that this PPI is both effective and well tolerated when administered in conjunction with NSAIDs. Thus, esomeprazole can be regarded as a useful option for prophylactic therapy in elderly patients receiving long-term NSAID therapy.

Bleeding peptic ulcer in the elderly: risk factors and prevention strategies

Peptic ulcer bleeding is a frequent and dramatic event with both a high mortality rate and a substantial cost for healthcare systems worldwide. It has been found that age is an independent predisposing factor for gastrointestinal bleeding, with the risk increasing significantly in individuals aged>65 years and increasing further in those aged>75 years. Indeed, bleeding incidence and mortality are distinctly higher in elderly patients, especially in those with co-morbidities. NSAID therapy and Helicobacter pylori infection are the most prevalent aetiopathogenetic factors involved in peptic ulcer bleeding. The risk of bleeding seems to be higher for NSAID- than for H. pylori-related ulcers, most likely because the antiplatelet action of NSAIDs impairs the clotting process. NSAID users may be classified as low or high risk, according to the absence or presence of one or more of the following factors associated with an increased risk of bleeding: co-morbidities; corticosteroid or anticoagulant co-therapy; previous dyspepsia, peptic ulcer or ulcer bleeding; and alcohol consumption. Different types of NSAIDs have been associated with different bleeding risk, but no anti-inflammatory drug, including selective cyclo-oxygenase (COX)-2 inhibitors, is completely safe for the stomach. Furthermore, even low-dose aspirin (acetylsalicylic acid) [<325 mg/day] and a standard dose of non-aspirin antiplatelet treatment (clopidogrel or ticlopidine) have been found to cause bleeding and mortality. No clear risk factor favouring H. pylori-related ulcer bleeding has been identified. Peptic ulcer bleeding prevention remains a challenge for the physician, but data are now available on use of a safer and cheaper strategy for both low- and high-risk patients. Unfortunately, despite the fact that several society and national guidelines have been formulated, these are poorly followed in clinical practice. Proton pump inhibitor (PPI) or misoprostol therapy and H. pylori eradication in NSAID-naive patients are the most commonly proposed strategies. Selective COX-2 inhibitor therapy in high-risk patients has also been suggested, but concerns over the possible cardiovascular adverse effects of some of these agents should be taken into account. Moreover, switching to selective COX-2 inhibitors in patients with previous bleeding is not completely risk free, and concomitant PPI therapy is also needed. H. pylori eradication is mandatory in all patients with peptic ulcer, and such an approach has been found to be significantly superior to PPI maintenance therapy. H. pylori eradication is frequently achieved with sequential therapy in elderly patients with peptic ulcer. In conclusion, upper gastrointestinal bleeding is a dramatic event with a high mortality rate, particularly in the elderly. Some effective preventative strategies are now available that should be implemented in clinical practice.

Influence of rabeprazole and lansoprazole on the pharmacokinetics of tacrolimus in relation to CYP2C19, CYP3A5 and MDR1 polymorphisms in renal transplant recipients

The objective of this study was to evaluate whether genetic polymorphisms of CYP2C19, CYP3A5 and MDR1 significantly impact the interaction between tacrolimus and rabeprazole or lansoprazole. Seventy-three recipients were randomly assigned after renal transplantation to receive repeated doses of tacrolimus for 28 days with a regimen of either 20 mg of rabeprazole or 30 mg of lansoprazole. Blood concentrations of tacrolimus were measured by microparticle enzyme immunoassay. The mean daily dose and the dose-adjusted area under the plasma concentration-time curves from 0 to 12 h (AUC(0-12)) of tacrolimus coadministered with rabeprazole or lansoprazole were the lowest and highest, respectively, in CYP2C19 poor metabolizers (PMs) having the CYP3A5*3/*3 genotype (0.084 and 0.112 mg/kg/day and 1.269 and 1.033 ng.h/ml/mg/kg, respectively). On the other hand, the mean dose-adjusted AUC(0-12) of tacrolimus coadministered with rabeprazole or lansoprazole were the highest in CYP2C19 PMs having the MDR13435CC+CT genotype, but not significantly. The present study indicates that there are significant interactions between tacrolimus and rabeprazole or lansoprazole in CYP2C19 PM renal transplant recipients bearing the CYP3A5*3/*3 genotypes. For recipients having these genetic polymorphisms, lower dosages of tacrolimus are required to achieve the target therapeutic index.

Treatment and dosing of Helicobacter pylori infection: when pharmacology meets clinic

Helicobacter pylori infection is a major cause of diseases located in the upper gastrointestinal tract. Successful eradication of the bacteria may improve H. pylori-related symptomatic complaints in functional dyspepsia, cure peptic ulcer disease and prevent gastric cancer. As vaccines are not available, the search for the optimal drug regimen has dominated the last decade. Today, most countries prefer a 7- to 10-day regimen containing a proton pump inhibitor, clarithromycin and amoxicillin as first-line treatment. An alternative (or second-line) treatment contains a proton pump inhibitor, bismuth, tetracycline and metronidazole. This review also highlights the impact of new drugs, new drug combinations, and their optimal dosing required to maximise clinical outcome.

Enantioselective disposition of rabeprazole in relation to CYP2C19 genotypes

AIM

Rabeprazole is metabolized to some extent by CYP2C19. The purpose of this study was to elucidate the pharmacokinetics of each rabeprazole enantiomer in three different CYP2C19 genotype groups.

METHODS

Twenty-four healthy subjects, of whom each each were homozygous extensive metabolizers (homEMs), heterozygous extensive metabolizers (hetEMs) and poor metabolizers (PMs) for CYP2C19, participated in our study. After a single oral dose of 20 mg of racemic rabeprazole, the plasma concentrations of the rabeprazole enantiomers were measured over the course of 24 h.

RESULTS

The area under the plasma concentration-time curves (AUC) of (R)-rabeprazole in homEMs, hetEMs and PMs were 1.8-, 2.2- and 2.4-fold, respectively, greater than those of (S)-rabeprazole; the relative AUC ratios of (R)- and (S)-rabeprazole in homEMs, hetEMs and PMs were 1:1.1:2.1 and 1:0.9:1.5, respectively. The mean maximum plasma concentrations (Cmax) of (R)-rabeprazole in homEMs, hetEMs and PMs were 1.7-, 1.9- and 1.8-fold higher, respectively, than those of the corresponding (S)-enantiomer (P<0.05). There was no difference between homEMs and PMs in the elimination half-life of (S)-rabeprazole, whereas the elimination half-life of (R)-rabeprazole was significantly longer in PMs than in homEMs [1.7 h (1.4, 2.0) (mean (95% confidence interval)]vs. 0.8 h (0.6, 1.0), respectively, P<0.0001).

CONCLUSIONS

(R)-Rabeprazole disposition was influenced to a greater degree by CYP2C19 genetic polymorphisms than was that of (S)-rabeprazole. The effect of CYP2C19 polymorphisms on the stereoselective disposition of rabeprazole was less than those of lansoprazole and omeprazole.

Enantioselective Disposition of Lansoprazole and Rabeprazole in Human Plasma

Lansoprazole is extensively metabolized by CYP2C19 and CYP3A4 in the liver, whereas rabeprazole is primarily converted non-enzymatically to rabeprazole-thioether, with only some being oxidized by CYP2C19 and CYP3A4. Lansoprazole and rabeprazole possess asymmetric sulfur in their chemical structure and have typically been used clinically as a racemic mixture. This article reviews the pharmacokinetic differences between enantiomers of lansoprazole and rabeprazole in relation to the CYP2C19 genotypes. In our studies in healthy Japanese subjects, the magnitude of contribution of each lansoprazole enantiomer for CYP2C19 was greater than that for CYP3A4. CYP2C19 influenced the disposition of (S)-lansoprazole to a greater extent than the (R)-enantiomer. The R/S ratios for the AUC of lansoprazole in CYP2C19 homEMs, hetEMs and PMs was 12.7, 8.5 and 5.8, respectively. On the other hand, (R)-rabeprazole disposition was influenced to a greater degree by CYP2C19 genetic polymorphisms than (S)-rabeprazole. However, the R/S ratios for the AUC of rabeprazole in CYP2C19 homEMs, hetEMs and PMs was only 1.8, 2.2 and 2.4, respectively, suggesting a lesser effect of CYP2C19 polymorphisms on the stereoselective disposition of rabeprazole compared to lansoprazole. Such a difference in the AUC between rabeprazole enantiomers is likely to be dependent on stereoselectivity in the CYP3A4-mediated metabolic conversion from rabeprazole-thioether to rabeprazole. Both enantiomers of these PPIs have been reported to possess equal potency. Therefore, particularly with lansoprazole, the use of (R)-lansoprazole alone would be highly desirable for use in clinical applications.