Effect of CYP2C19 genetic polymorphisms on the efficacy of proton pump inhibitor-based triple therapy for Helicobacter pylori eradication: a meta-analysis

[Future trends of Helicobacter pylori eradication therapy in Korea]

The prevalence of Helicobacter pylori infection in Korea shows a decreasing trend and has changed to that of developed country, especially for those below 30 years old. However, the primary antibiotic resistance rates are higher than those of developed countries. The reason for the decrease in the efficacy of standard triple therapy is mainly due to the increase in the resistance against clarithromycin. Sequential therapy seems to be more effective than the standard triple therapy, but the intention-to-treat eradication rate of sequential therapy in Korea, which is mostly under 80.0%, is still not satisfactory. Therefore, a promising regimen is needed. Recently, the Japanese health insurance system admitted 'H. pylori-infected gastritis'as an indication of eradication. Furthermore, the Kyoto Consensus Meeting on H. pylori Gastritis held from January 30th to February 1st, 2014, proposed that 'all H. pylori positive patients should be offered to receive H. pylori eradication'. This suggests that the concept of eradication has been changed from 'treatment' to 'prevention'. Various individualized tailored therapy based on the polymorphism, age and other demographic factors and antibiotic resistance has been attempted to maximize H. pylori eradication therapy. The aim of this article is to review the current epidemiology, H. pylori resistance state, treatment guideline, and to assess the possible future strategy and treatment for H. pylori infection in Korea.

Optimizing clarithromycin-containing therapy for Helicobacter pylori in the era of antibiotic resistance

The efficacy of triple therapy for Helicobacter pylori infection has dramatically declined over the last decade, largely related to increasing clarithromycin resistance rates. From a microbiological standpoint, bismuth quadruple therapy is the ideal replacement since it combines drugs for which resistance does not impair its efficacy. Nonetheless, several obstacles such as availability, complexity or tolerance prevent a general implementation of bismuth quadruple therapy, so non-bismuth quadruple regimens remain the best first-line treatment in clinical practice in many geographical areas. We review the rationale and efficacy of several optimization tools (increasing the length of duration, high-dose acid suppression, probiotics), which have been largely evaluated over the last 5 years to increase the effectiveness of standard triple therapy. Then, we update available evidence on the effectiveness of several non-bismuth quadruple therapies (sequential, concomitant, hybrid, miscellaneous therapy), which have gained interest lately. We also revise evidence on the efficacy of the aforementioned optimization tools for non-bismuth quadruples schemes and, finally we provide a novel regionalized therapeutic algorithm, based on novel formulas recently developed for predicting the outcome of non-bismuth quadruple regimens, upon local antibiotic resistance rates.

Treatment of Helicobacter pylori infection: meeting the challenge of antimicrobial resistance

Treatment of Helicobacter pylori (H. pylori) infection is paramount for the management of prevalent gastrointestinal disorders including peptic ulcer disease and gastric cancer. Due to the wide increase in prevalence of H. pylori resistance to antibiotics, clarithromycin-based triple therapies are not any more suitable for unconditional empiric use, and should not be recommended, unless local resistance to this antibiotic is low (< 20%). Alternative strategies have been proposed to overcome the issue of increasing clarithromycin resistance, and some of them are already implemented in clinical practice. These comprise: (1) adoption of novel, more effective, empirical treatments: bismuth quadruple, sequential, non-bismuth quadruple (concomitant), dual-concomitant (hybrid), and levofloxacin-based regimens, the latter mainly designated as second-line/rescue options; (2) perspectives for a susceptibility-guided (tailored) therapeutic approach based on culture-free molecular testing methods; and (3) adjunct use of probiotics to improve eradication rates. The present article is aimed to provide a comprehensive overview of current and emerging strategies in the treatment of H. pylori infection, focusing on the challenge of antimicrobial resistance.

Factors affecting first-line triple therapy of Helicobacter pylori including CYP2C19 genotype and antibiotic resistance

BACKGROUND

Emerging evidence shows that the eradication rate of proton pump inhibitor (PPI)-based triple therapy for the first-line treatment of Helicobacter pylori (H. pylori) has decreased.

AIMS

To clarify the trend of eradication rate of PPI-based triple therapy and to assess the related factors in Korea during the past decade.

METHODS

We prospectively prescribed the triple regimen for seven days (PPI + amoxicillin 1.0 g + clarithromycin 500 mg, twice a day) from March 2003 to May 2013 in 2,202 H. pylori-positive patients. Antibiotic susceptibility tests were performed by the agar dilution method, and the CYP2C19 genotype was determined by the PCR method.

RESULTS

In the past decade, the annual eradication rate showed a decreasing trend in intention-to-treat and per-protocol analyses (P = 0.001, both). The antibiotic resistance was increased to amoxicillin (7.2-17.2%, P = 0.003) and clarithromycin (23.2-37.3%, P = 0.010) during the study period. The poor metabolizer genotype of CYP2C19 showed a high eradication rate compared to the extensive metabolizer (86.8 vs. 78.2%, P = 0.035). In addition, age ≥ 50 years, female gender, BMI < 25 kg/m(2), amoxicillin and/or clarithromycin resistance were associated with treatment failure on univariate analysis. However, on multivariate analysis, clarithromycin resistance was the only significant factor for treatment failure (OR, 12.76; 95% CI, 5.58-29.18; P < 0.001).

CONCLUSIONS

An increase in clarithromycin resistance has led to decreased eradication rate of first-line triple therapy, and; hence, a new strategy is needed to improve the eradication rate of H. pylori.

Optimum duration of regimens for Helicobacter pylori eradication

BACKGROUND

The optimal duration for Helicobacter pylori (H. pylori) eradication therapy is controversial, with recommendations ranging from 7 to 14 days. Several systematic reviews have attempted to address this issue but have given conflicting results and limited their analysis to proton pump inhibitor (PPI), two antibiotics (PPI triple) therapy. We performed a systematic review and meta-analysis to investigate the optimal duration of multiple H. pylori eradication regimens.

OBJECTIVES

The primary objective was to assess the relative effectiveness of different durations (7, 10 or 14 days) of a variety of regimens for eradicating H. pylori. The primary outcome was H. pylori persistence. The secondary outcome was adverse events.

SEARCH METHODS

The Cochrane Library, MEDLINE, EMBASE, and CINAHL were searched up to December 2011 to identify eligible randomised controlled trials (RCTs). We also searched the proceedings of six conferences from 1995 to 2011, dissertations and theses, and grey literature. There were no language restrictions applied to any search.

SELECTION CRITERIA

Only parallel group RCTs assessing the efficacy of one to two weeks duration of first line H. pylori eradication regimens in adults were eligible. Within each regimen, the same combinations of drugs at the same dose were compared over different durations. Studies with at least two arms comparing 7, 10, or 14 days were eligible. Enrolled participants needed to be diagnosed with at least one positive test for H. pylori on the basis of a rapid urease test (RUT), histology, culture, urea breath test (UBT), or a stool antigen test (HpSA) before treatment. Eligible trials needed to confirm eradication of H. pylori as their primary outcome at least 28 days after completion of eradication treatment. Trials using only serology or a polymerase chain reaction (PCR) to determine H. pylori infection or eradication were excluded.

DATA COLLECTION AND ANALYSIS

Study eligibility and data extraction were performed by two independent review authors. Data analyses were performed within each type of intervention, for both primary and secondary outcomes. The relative risk (RR) and number needed to treat (NNT)/number needed to harm (NNTH) according to duration of therapy were calculated using the outcomes of H. pylori persistence and adverse events. A random-effects model was used. Subgroup analyses and sensitivity analyses were planned a priori.

MAIN RESULTS

In total, 75 studies met the inclusion criteria. Eight types of regimens were reported with at least two comparative eligible durations. They included: PPI + two antibiotics triple therapy (n = 59), PPI bismuth-based quadruple therapy (n = 6), PPI + three antibiotics quadruple therapy (n = 1), PPI dual therapy (n = 2), histamine H2-receptor antagonist (H₂RA) bismuth quadruple therapy (n = 3), H₂RA bismuth-based triple therapy (n = 2), H₂RA + two antibiotics triple therapy (n = 3), and bismuth + two antibiotics triple therapy (n = 2). Some studies provided data for more than one regimen or more than two durations.For the PPI triple therapy, 59 studies with five regimens were reported: PPI + clarithromycin + amoxicillin (PCA); PPI + clarithromycin + a nitroimidazole (PCN); PPI + amoxicillin + nitroimidazole (PAN); PPI + amoxicillin + a quinolone (PAQ); and PPI + amoxicillin + a nitrofuran (PANi). Regardless of type and dose of antibiotics, increased duration of PPI triple therapy from 7 to 14 days significantly increased the H. pylori eradication rate (45 studies, 72.9% versus 81.9%), the RR for H. pylori persistence was 0.66 (95% CI 0.60 to 0.74), NNT was 11 (95% CI 9 to 14). Significant effects were seen in the subgroup of PCA (34 studies, RR 0.65, 95% CI 0.57 to 0.75; NNT 12, 95% CI 9 to 16); PAN (10 studies, RR 0.67, 95% CI 0.52 to 0.86; NNT = 11, 95% CI 8 to 25); and in PAQ (2 studies, RR 0.37, 95% CI 0.16 to 0.83; NNT 3, 95% CI 2 to 10); but not in PCN triple therapy (4 studies, RR 0.87, 95% CI 0.71 to 1.07). Significantly increased eradication rates were also seen for PPI triple therapy with 10 versus 7 days (24 studies, 79.9% versus 75.7%; RR 0.80, 95% CI 0.72 to 0.89; NNT 21, 95% CI 15 to 38) and 14 versus 10 days (12 studies, 84.4% versus 78.5%; RR 0.72, 95% CI 0.58 to 0.90; NNT 17, 95% CI 11 to 46); especially in the subgroup of PAC for 10 versus 7 days (17 studies, RR 0.80, 95% CI 0.70 to 0.91) and for 14 versus 10 days (10 studies, RR 0.69, 95% CI 0.52 to 0.91). A trend towards increased H. pylori eradication rates was seen with increased duration of PCN for 10 versus 7 days, and of PAN for 10 versus 7 days and 14 versus 10 days, though this was not statistical significant. The proportion of patients with adverse events, defined by authors, was marginally significantly increased only between 7 days and 14 days (15.5% versus 19.4%; RR 1.21, 95% CI 1.06 to 1.37; NNTH 31, 95% CI 18 to 104) but not for other duration comparisons. The proportion of patients discontinuing treatment due to adverse events was not significantly different between treatment durations.Only limited data were reported for different durations of regimens other than PPI triple therapy. No significant difference of the eradication rate was seen for all regimens according to different durations except for H₂RA bismuth quadruple therapy, where a significantly higher eradication rate was seen for 14 days versus 7 days, however only one study reported outcome data.

AUTHORS' CONCLUSIONS

Increasing the duration of PPI-based triple therapy increases H. pylori eradication rates. For PCA, prolonging treatment duration from 7 to 10 or from 10 to 14 days is associated with a significantly higher eradication rate. The optimal duration of therapy for PCA and PAN is at least 14 days. More data are needed to confirm if there is any benefit of increasing the duration of therapy for PCN therapy. Information is limited for regimens other than PPI triple therapy; more studies are needed to draw meaningful conclusions for optimal duration of other H. pylori eradication regimens.

Effects of CYP2C19 loss-of-function variants on the eradication of H. pylori infection in patients treated with proton pump inhibitor-based triple therapy regimens: a meta-analysis of randomized clinical trials

Background

There are inconsistent conclusions about whether CYP2C19 variants could affect H. pylori eradication rate in patients treated with the proton pump inhibitor (PPI)-based therapy. We therefore performed a meta-analysis of randomized clinical trials (RCTs) to re-evaluate the impact of CYP2C19 variants on PPI-based triple therapy for the above indication.

Methods

All relevant RCTs in the PubMed, Cochrane Library, EMBASE, Web of Science and two Chinese databases (up to February 2013) were systematically searched, and a pooled analysis was performed with the odds ratio (OR) and 95% confidence interval (CI) by the STATA software.

Results

Sixteen RCT datasets derived from 3680 patients were included. There was no significant heterogeneity across the data available in this meta-analysis. There were significant differences in that rate between homozygous (HomEMs) and heterozygous (HetEMs) extensive metabolizers (OR 0.724; 95% CI 0.594–0.881), between HomEMs and poor metabolizers (PM) (OR 0.507; 95%CI 0.379–0.679), or between HetEMs and PMs (OR 0.688; 95%CI 0.515–0.920), regardless of the PPI being taken. Furthermore, sub-analysis of individual PPIs was carried out to explore the difference across all the PPIs used. A significantly low rate was seen in HomEMs vs. HetEMs taking either omeprazole (OR 0.329; 95%CI 0.195–0.553) or lansoprazole (OR 0.692; 95%CI 0.485–0.988), and also in HomEMs vs. PMs for omeprazole (OR 0.232; 95%CI 0.105–0.515) or lansoprazole (OR 0.441; 95%CI 0.252–0.771). However, there was no significant difference between HetEMs and PMs taking either one. No significant differences were observed for rabeprazole or esomeprazole across the CYP2C19 genotypes of interest.

Conclusions

Carriage of CYP2C19 loss-of-function variants is associated with increased H. pylori eradication rate in patients taking PPI-based triple therapies when omeprazole or lansoprazole is chosen. However, there is no a class effect after use of rabeprazole or esomeprazole.

The effect of rabeprazole on LES tone in experimental rat model

INTRODUCTION

Despite adequate treatment with proton pump inhibitors (PPIs), symptoms of gastroesophageal reflux disease (GERD) may remain persistent as well as Barrett's esophagus may emerge. It may be proposed that the relaxant effect of PPIs on the smooth muscles may lead to resistance of symptoms. The aim of this study is to investigate effects of rabeprazole on the lower esophageal sphincter (LES) pressure with a rat model.

MATERIALS AND METHODS

Sixteen rats were grouped as control and treatment groups. After obtaining LES tissues followed by a 60 min equilibration period for stabilization, contractile response to carbachol was obtained by application of single dose of carbachol to have a final concentration of 10(-6) M in the organ bath. After the contractions reached a plateau, concentration-response relationships for rabeprazole were obtained in a cumulative manner in the treatment group.

RESULTS

In the carbachol contracted LES preparations; 1.5 × 10(-6) and 1.5×10(-5) M of rabeprazole caused 6.08% and 11.34% relaxations respectively which were not statistically significant. However, mean integral relaxation value for 4.5 × 10(-5) M of rabeprazole was 17.34% and this relaxation was significant compared with controls.

CONCLUSIONS

In the present study, rabeprazole caused no direct significant change in LES tone in the therapeutic dose range applied to the organ bath. However, rabeprazole at the high dose caused a significant decrease in the LES tone.

Individualized therapy for gastroesophageal reflux disease: potential impact of pharmacogenetic testing based on CYP2C19

The main therapeutic agent for gastroesophageal reflux disease (GERD) is a proton pump inhibitor (PPI). Plasma levels and the acid inhibitory effect of PPIs depend on the activity of cytochrome P450 (CYP) 2C19, which is polymorphic. Genotypes of CYP2C19 are classified into three groups: rapid metabolizers (RMs: *1/*1), intermediate metabolizers (IMs: *1/*X), and poor metabolizers (PMs: *X/*X), where *1 and X represent the wild type and the mutant allele, respectively. RMs include ultra-rapid metabolizers, who possess the CYP2C19*17 allele. The pharmacokinetics and pharmacodynamics of PPIs differ among different CYP2C19 genotype groups. Plasma PPI levels and intragastric pH values during PPI treatment are lowest in the RM group, intermediate in the IM group, and highest in the PM group. These CYP2C19-genotype-dependent differences in the pharmacokinetics and pharmacodynamics of PPIs influence the healing and recurrence of GERD during PPI treatment, suggesting the need for CYP2C19 genotype-based tailored therapy for GERD. CYP2C19 pharmacogenetics should be taken into consideration for the personalization of PPI-based therapy. However, the clinical usefulness of CYP2C19 genotype testing in GERD therapy should be verified in clinical studies.

Individualized therapy for gastroesophageal reflux disease: potential impact of pharmacogenetic testing based on CYP2C19

The main therapeutic agent for gastroesophageal reflux disease (GERD) is a proton pump inhibitor (PPI). Plasma levels and the acid inhibitory effect of PPIs depend on the activity of cytochrome P450 (CYP) 2C19, which is polymorphic. Genotypes of CYP2C19 are classified into three groups: rapid metabolizers (RMs: *1/*1), intermediate metabolizers (IMs: *1/*X), and poor metabolizers (PMs: *X/*X), where *1 and X represent the wild type and the mutant allele, respectively. RMs include ultra-rapid metabolizers, who possess the CYP2C19*17 allele. The pharmacokinetics and pharmacodynamics of PPIs differ among different CYP2C19 genotype groups. Plasma PPI levels and intragastric pH values during PPI treatment are lowest in the RM group, intermediate in the IM group, and highest in the PM group. These CYP2C19-genotype-dependent differences in the pharmacokinetics and pharmacodynamics of PPIs influence the healing and recurrence of GERD during PPI treatment, suggesting the need for CYP2C19 genotype-based tailored therapy for GERD. CYP2C19 pharmacogenetics should be taken into consideration for the personalization of PPI-based therapy. However, the clinical usefulness of CYP2C19 genotype testing in GERD therapy should be verified in clinical studies.

Helicobacter pylori eradication with ecabet sodium, omeprazole, amoxicillin, and clarithromycin versus bismuth, omeprazole, amoxicillin, and clarithromycin quadruple therapy: a randomized, open-label, phase IV trial

BACKGROUND

Helicobacter pylori infection is a substantial public health problem and plays etiological role in the pathogenesis of many gastroduodenal disorders. The addition of ecabet sodium is proven to improve the efficacy of the standard triple therapy. Our aim was to assess the efficacy and safety of ecabet sodium-containing quadruple therapy versus 10-day bismuth-containing quadruple therapy for H. pylori eradication.

MATERIALS AND METHODS

We did a randomized, open-label, phase IV trial in four cities (eight sites) in China, comparing the efficacy and safety of 10-days ecabet sodium-containing versus bismuth-containing quadruple therapy in adults with H. pylori infection. Eligible patients were randomly assigned treatment and monitored H. pylori eradication by negative [13C]/[14C] urea breath test 28 days after the treatment as the primary outcome. Symptoms improvement and side effects were the secondary outcome.

RESULTS

A total of 311 H. pylori-positive subjects were enrolled: 155 were assigned ecabet sodium quadruple therapy and 156 bismuth quadruple therapy. The eradication rates with ecabet sodium-containing and bismuth-containing quadruple regimens were 68.4% (106/155) and 68.0% (106/156) p = .9339 intention-to-treat (ITT) and 75.4% (104/138) and 77.0% (104/135) p = .7453 per-protocol (PP), respectively. The eradication rates for the ecabet sodium quadruple regimen differed significantly between cities (e.g., 81.2% ITT and 89.6% PP in Shanghai and 50% ITT and 53.5% PP in Xi'an). The symptom improvements and safety profiles were also similar for both treatments.

CONCLUSIONS

Neither 10-day Ecabet sodium-containing quadruple therapy or 10-day bismuth-containing quadruple therapy can be recommended as empiric therapy in cities with high antibiotic resistance rate of China.

Clinical Application of Pharmacogenomics

The purpose of this review is to discuss the clinical application of pharmacogenomics for select drug therapies (eg, proton pump inhibitors [PPIs], codeine, and carbamazepine) and to highlight limitations and challenges that preclude implementation of pharmacogenomics into clinical practice. Genetic polymorphisms of cytochrome P450 (CYP) enzymes and the presence of the human leukocyte antigen ( HLA) -B*1502 allele influence drug disposition and/or response. A portion of PPI pharmacokinetic and pharmacodynamic variability can be explained by CYP2C19 genotype. However, conflicting evidence exists related to Helicobacter pylori cure rates based on CYP2C19 genotype. For codeine, adverse drug reactions in neonates through breast-feeding from CYP2D6 ultra-rapid metabolizers have been reported. However, there is lack of conclusive evidence regarding the overall influence of CYP2D6 polymorphisms on codeine efficacy and toxicity. Although CYP2C19 and CYP2D6 genotyping tests are available, clinical utility remains low. The presence of the HLA-B*1502 allele is associated with carbamazepine-induced Stevens-Johnson syndrome (SJS) and/or toxic epidermal necrolysis (TEN). Pharmacogenomic testing is required prior to initiating carbamazepine in high-risk patients. Lack of sufficient resources, provider knowledge, and ethical, legal, and social issues are several limitations and challenges to implementing pharmacogenomic testing in clinical practice.

CYP2C19 polymorphism affects single-dose pharmacokinetics of oral pantoprazole in healthy volunteers

Objectives

Pantoprazole is metabolized by cytochrome P450 2 C19, which shows genetic polymorphism. The effect of CYP2C19 polymorphism on single-dose pharmacokinetics of oral pantoprazole in healthy volunteers was evaluated.

Methods

Pantoprazole pharmacokinetics was determined in 32 healthy volunteers after a 40-mg single oral dose of the drug.

Results

Carriers of CYP2C19*2/*2 (n = 2) were characterized by higher, starting from 3.5 h post dose, plasma concentrations of pantoprazole in comparison to wild-type (CYP2C19*1/*1, n = 6) volunteers. In subjects with CYP2C19*17/*17 genotype (n = 6) significantly lower plasma concentrations of the drug vs CYP2C19*1/*1 carriers, were observed from 3.0 h after oral pantoprazole administration. Carriers of CYP2C19*1/*17 (n = 6) and CYP2C19*2/*17 (n = 6) displayed concentration–time profiles comparable to wild-type subjects. CYP2C19*2/*2 volunteers showed a decrease in terminal elimination rate constant (λ_z) by 83.3%, prolongation of terminal half-life (t_½) by 572%, a rise in area under the concentration–time curve (AUC) and mean residence time (MRT) by 506% and 259% respectively. Heterozygotes, i.e.. CYP2C19*1/*2 vs CYP2C19*1/*1 were characterized by higher AUC (4.38 ± 1.00 mg⋅h/L vs 3.00 ± 1.02 mg⋅h/L, p < 0.05) and C_max (2.13 ± 0.42 mg/L vs 1.61 ± 0.35 mg/L, p < 0.05) respectively. A significant reduction in MRT (3.83 ± 0.82 h vs 2.73 ± 0.23 h, p < 0.05) in carriers of CYP2C19*17/*17 vs CYP2C19*1/*1 genotypes was observed. Population modeling confirmed the influence of *1/*2, *2/*2, and *17/*17 genotypes on the pharmacokinetics of pantoprazole. The lowest population oral clearance was assessed in the carriers of genotype *2/*2 (3.68 L/h) and the highest value in subjects with genotype *17/*17 (31.13 L/h).

Conclusion

These data suggest that CYP2C19 polymorphism is an important determinant of pantoprazole pharmacokinetics.

Update on the pharmacogenomics of proton pump inhibitors

Proton pump inhibitors (PPIs) are widely used for the treatment of gastroesophageal reflux disease as well as other acid-related disorders. PPIs are metabolized primarily via the CYP2C19 and CYP3A4 isoenzymes; their activity is influenced both by exogenous and endogenous (pharmacogenetic) factors. The CYP2C19 polymorphism affects the metabolism of PPIs, causing large individual pharmacokinetic variations. Differences in the CYP2C19-mediated metabolism can produce marked interpatient variability in acid suppression, in drug-interaction potential and in clinical efficacy. Understanding the pharmacokinetic properties of PPIs and examining the pharmacogenetic alterations may help clinicians optimize PPI therapy and administer individual treatment, especially to nonresponder patients with gastroesophageal reflux disease or ulcer or after failed eradication therapy.

Effectiveness of ranitidine bismuth citrate and proton pump inhibitor based triple therapies of Helicobacter pylori in Turkey

Background

Helicobacter pylori infection is the main cause of gastritis, gastroduodenal ulcer disease, MALT lymphoma, and adenocarcinoma of the stomach. The reported prevalence of H. pylori in the adult population in Turkey is 67.6%–81.3%. A national meta-analysis showed that the average H. pylori eradication rate with proton pump inhibitor-based triple regimens in Turkey had decreased from 84% in 1997 to 55.3% in 2004, suggesting a need to evaluate alternative regimens.

Materials and methods

The study was a prospective, single-center trial with a parallel group design. After the selection procedure, consecutive out-patients were assigned to one of six study groups using random sampling numbers. All patients received amoxicillin 1,000 mg b.i.d. and clarithromycin 500 mg b.i.d. along with ranitidine bismuth citrate 400 mg b.i.d., or omeprazole 20 mg b.i.d., or lansoprazole 30 mg b.i.d., or rabeprazole 20 mg b.i.d., or pantoprazole 40 mg b.i.d., or esomeprazole 40 mg b.i.d. for 14 days.

Results

When we look at the eradication rates of the treatment groups, only two groups (ranitidine bismuth citrate and rabeprazole groups) had eradication rates greater than 80%, both at intention to treat and per protocol analyses. The other four groups (omeprazole, lansoprazole, pantoprazole, and esomeprazole groups) showed statistically significant lower eradication rates both at intention to treat (between 57.6 and 66.7%) and per protocol (between 60.3 and 72.1%) analyses when compared with ranitidine bismuth citrate and rabeprazole groups (p<.05).

Conclusion

Ranitidine bismuth citrate and/or rabeprazole based triple therapies must be preferred for the first-line treatment of H. pylori infection.

Clopidogrel and proton pump inhibitors: influence of pharmacological interactions on clinical outcomes and mechanistic explanations

Dual antiplatelet therapy with aspirin and clopidogrel is associated with a significant reduction in vascular ischemic events; however, gastrointestinal bleeding events are a major concern in high-risk and older patients. Clinical practice guidelines recommend combination therapy with proton pump inhibitors (PPI) and dual antiplatelet therapy to attenuate gastrointestinal bleeding risk. In addition, high on-treatment platelet reactivity has been associated with recurrent ischemic events. Whether or not the pharmacological interaction between clopidogrel and PPI, which results in diminished antiplatelet effect, adversely influences clinical efficacy is highly controversial and the subject of debate. Based on largely anecdotal post-hoc analyses, the U.S. Federal Drug Administration's and European Medicines Agency's recommendations discourage PPI use (particularly omeprazole) in patients treated with clopidogrel. However, many American College of Cardiology/American Heart Association/Society for Cardiovascular Angiography and Interventions experts do not support change in clinical practice guidelines recommendations without adequately powered, prospective, randomized clinical trial data.

[Evidence and uncertainties on the clinical use of proton pump inhibitors]

Proton pump inhibitors (PPI) are the most potent and effective drugs for the control of gastric acid secretion and constitute one of the most widely prescribed pharmacological groups worldwide. The safety and efficacy of PPI have been demonstrated in clinical practice and these drugs are currently the treatment of choice in peptic ulcer diseases, Helicobacter pylori infection, gastroesophageal reflux disease, nonsteroidal antiinflammatory drug gastropathy and functional dyspepsia. However, despite the excellent pharmacological profile of current PPI, their rapidity of action may be insufficient in some diseases, 24-hour acid inhibition is not always achieved and - to a greater or lesser extent depending on the distinct molecules of the PPI - there is interindividual variability in gastric antisecretory efficacy, depending on genetic polymorphism of CYP2C19, which could affect individual metabolism of the distinct PPI. New generations of these drugs will probably eliminate these deficiencies.

Pharmacologic aspects of eradication therapy for Helicobacter pylori Infection

The commonly used regimens for the eradication of Helicobacter pylori infection consist of administration of proton pump inhibitors (PPIs) and 1 to 3 antimicrobial agents, such as amoxicillin, clarithromycin, metronidazole, fluoroquinolone, or tetracycline. Each agent has its own pharmacologic characteristics. PPIs are metabolized by cytochrome P450 2C19 (CYP2C19), which is polymorphic. CYP2C19 genotypic differences in the pharmacokinetics and pharmacodynamics of PPIs influence the eradication rates of H pylori infection by PPI-containing regimens. Amoxicillin is a time-dependent antibiotic, whereas clarithromycin, metronidazole, tetracycline, and fluoroquinolone are not. The plasma half-life of antimicrobial agents also differs among these antibiotics. To achieve consistently high eradication rates, the eradication regimens must be designed based on a good understanding of the resistance patterns of the bacteria and the pharmacologic characteristics of the agents used for H pylori eradication therapy.

First-line eradication of Helicobacter pylori: Are the standard triple therapies obsolete? A different perspective

Studies concerning the eradication of Helicobacter pylori have resulted in a proliferation of meta-analyses. To date, there are 303 meta-analyses cited in PubMed, 113 dealing with the therapy of the infection. A chronological analysis of the results of meta-analyses performed between 1998 and 2010 shows that first-line standard triple therapies achieved eradication rates on an intention-to-treat basis of around 80%; prolonging treatment to 14, but not 10 d should improve the results. The proton pump inhibitors have a similar efficiency, and giving a double dose is more efficient than the standard doses of these drugs. Triple and quadruple therapies proved to be equivalent. Based on meta-analytical data, the decrease in efficiency over time cannot be substantiated: eradication rates < 80% followed from the introduction of triple therapies. As alternatives, ranitidine bismuth citrate-, levofloxacin- or furazolidone-based therapies were shown to obtain the same eradication rates as standard triple regimens. Sequential therapies and quadruple non-bismuth-based therapies were superior to standard triple therapies but their use is limited to certain countries. In the author’s opinion, and from a meta-analytical viewpoint, standard triple therapies cannot yet be considered obsolete. Furthermore, non-inferiority trials are proposed for the future, including assessment of local contemporary antimicrobial resistance profiles and the CagA and CYP2C19 status of the enrolled patients.

Changes in 12-Year First-Line Eradication Rate of Helicobacter pylori Based on Triple Therapy with Proton Pump Inhibitor, Amoxicillin and Clarithromycin

A triple therapy based on a proton pump inhibitor (PPI), amoxicillin (AMPC), and clarithromycin (CAM) is recommended as a first-line therapy for Helicobacter pylori (H. pylori) eradication and is widely used in Japan. However, a decline in eradication rate associated with an increase in prevalence of CAM resistance is viewed as a problem. We investigated CAM resistance and eradication rates over time retrospectively in 750 patients who had undergone the triple therapy as first-line eradication therapy at Nagoya City University Hospital from 1995 to 2008, divided into four terms (Term 1: 1997-2000, Term 2: 2001-2003, Term 3: 2004-2006, Term 4: 2007-2008). Primary resistance to CAM rose significantly over time from 8.7% to 23.5%, 26.7% and 34.5% while the eradication rate decreased significantly from 90.6% to 80.2%, 76.0% and 74.8%. Based on the PPI type, significant declines in eradication rates were observed with omeprazole or lansoprazole, but not with rabeprazole. A decrease in the H. pylori eradication rate after triple therapy using a PPI + AMPC + CAM has been acknowledged, and an increase in CAM resistance is considered to be a factor. From now on, a first-line eradication regimen that results in a higher eradication rate ought to be investigated.

The Influence of CYP2C19 Polymorphism on Eradication of Helicobacter pylori: A Prospective Randomized Study of Lansoprazole and Rabeprazole

BACKGROUND/AIMS

The CYP2C19 polymorphism plays an important role in the metabolism of various proton-pump inhibitors. Several trials have produced conflicting data on eradication rates of Helicobacter pylori (H. pylori) among CYP2C19 genotypes. We investigated whether the CYP2C19 genotype affects the eradication rate of H. pylori by direct comparing the effects of lansoprazole- and rabeprazole-based triple therapies.

METHODS

A total of 492 patients infected with H. pylori was randomly treated with either 30 mg of lansoprazole or 20 mg of rabeprazole plus 500 mg of clarithromycin and 1,000 mg of amoxicillin twice daily for 1 week. CYP2C19 genotype status was determined by a PCR-restriction-fragment-length polymorphism method. After 7 to 8 weeks, H. pylori status was evaluated by a C(13)-urea breath test.

RESULTS

Four hundred and sixty-three patients were analyzed, and the eradication rate was 75.2% in a per-protocol analysis. Eradication rates for the lansoprazole regimen (n=234) were 73.8%, 80.7%, and 85.4% in the homozygous extensive (HomEM), heterozygous extensive (HetEM), and poor metabolizers (PM) groups, respectively (p=0.303). In the case of the rabeprazole regimen (n=229), the eradication rates were 68.6%, 73.0%, and 71.9% in the HomEM, HetEM, and PM groups, respectively (p=0.795).

CONCLUSIONS

The efficacies of triple therapies that include lansoprazole or rabeprazole are not affected by CYP2C19 genetic polymorphisms.

Cytochrome P450 loss-of-function polymorphism genotyping on the Agilent Bioanalyzer and clinical application

Responses to toxins and drugs, even to standard medical drug treatment regimens, can vary significantly between individuals. Similar dosages can have divergent results due to polymorphisms in the genes that code for the enzymes responsible for the metabolism of drugs. The focus of this report is to describe our exploration of the personalized medicine approach for patient care at Sydney West Area Health Service. We would like to demonstrate the importance of this approach as it is the subject of debate in the medical and scientific community. The critical points in this debate are the cost of testing, laboratory space required and clinical application. We have shown that a simple approach and instruments like the Agilent Bioanalyzer could be cost effective for laboratory operation. The Agilent Bioanalyzer (Agilent Technologies, CA, USA) can be used for proteins, DNA and cell studies. Hence, reduced cost of instruments, laboratory space requirements, maintenance and operational costs are great advantages of this technology, especially for development and research laboratories.

Advances in clinical research on the interaction between proton pump inhibitors and clopidogrel

As a new antiplatelet drug, clopidogrel is the cornerstone of drug treatment for coronary artery disease. However, clinical use of clopidogrel frequently leads to gastrointestinal injury or increases the risk of gastrointestinal bleeding. To prevent clopidogrel-associated gastrointestinal injury, concomitant proton pump inhibitors (PPIs) have been used widely in clinical practice. However, recent studies show that treatment with clopidogrel plus PPIs can increase the incidence of adverse cardiovascular events. Despite being controversial, this finding has attracted wide attention from clinicians. This article will review the recent advances in clinical research on the interaction between proton pump inhibitors and clopidogrel.

Cost effectiveness of pharmacogenomics: a critical and systematic review

The use of pharmacogenetic testing in clinical practice is limited thus far. A potential barrier to the widespread implementation of pharmacogenetic testing is the lack of evidence on whether testing provides good value for money. The objective of this review was to provide a systematic and critical review of economic evaluations of pharmacogenetic testing. A literature search using publically available databases was performed for articles published up to October 2009. To be included, studies had to meet the definition of being a pharmacogenomic study (defined as use of information on human genetic variation to target drug therapy) and an economic evaluation (defined as an evaluation of both costs and clinical outcomes). Articles that met these criteria were subsequently reviewed and graded using the Quality of Health Economic Studies (QHES) instrument. Lastly, the evidence for biomarker validity and utility were qualitatively assessed using expert opinion. A total of 34 articles were identified using our defined criteria. The most common disease category was thromboembolic-related diseases (26%), while the most common biomarkers were thiopurine methyltransferase and cytochrome P450 2C9 (18% each). Almost all studies were published after 2004 (91%). Two types of studies were identified: cost-effectiveness studies and cost-utility studies, with roughly half of the overall studies being cost-utility studies (53%) and a majority of these published within the last 3 years. The average quality score was 77 (range 29-99). Of the biomarkers reviewed, it was estimated that most had demonstrated clinical validity, but only two had demonstrated clinical utility. Despite a recent increase in the number of economic evaluations of pharmacogenetic applications, further studies examining the clinical validity and utility of these biomarkers are needed to support cost-effectiveness assessments.

Helicobacter pylori: diagnosis and treatment

PURPOSE OF REVIEW

Multiple diagnostic methods and treatment strategies have been developed to detect and treat the Helicobacter pylori infection. Many of them have stood the test of time; others lost their value with the introduction of new test and treatment modalities. This review focuses on the current diagnostic methods and their clinical implications, as well as on established and novel treatment strategies.

RECENT FINDINGS

The increasing antimicrobial resistance has resulted in a decline of the success rate of recommended eradication regimens. The current guidelines recommend as first-line treatment clarithromycin, amoxicillin or metronidazole, and proton pump inhibitor twice daily, but recent studies have demonstrated an increasing eradication failure with these regimens. Several treatment modifications have been adopted regarding duration and combination of substances.

SUMMARY

The currently recommended first-line treatments are effective and well tolerated. In areas with high antimicrobial resistance rates, new antibiotic combinations and modifications in the sequence of drug administration are proposed as alternative treatment options to standard triple therapy. Future treatment strategies have to focus on regional antimicrobial resistance adopted treatment selection and the development of new antibiotics.