Clinical Trials Study
Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Dec 28, 2015; 21(48): 13548-13554
Published online Dec 28, 2015. doi: 10.3748/wjg.v21.i48.13548
First-line eradication for Helicobacter pylori-positive gastritis by esomeprazole-based triple therapy is influenced by CYP2C19 genotype
Yoshimasa Saito, Hiroshi Serizawa, Yukako Kato, Masaru Nakano, Masahiko Nakamura, Hidetsugu Saito, Hidekazu Suzuki, Takanori Kanai
Yoshimasa Saito, Hiroshi Serizawa, Yukako Kato, Masaru Nakano, Division of Gastroenterology, Kitasato Institute Hospital, Minato-ku, Tokyo 108-8641, Japan
Yoshimasa Saito, Hidetsugu Saito, Division of Pharmacotherapeutics, Keio University Faculty of Pharmacy, Minato-ku, Tokyo 105-8512, Japan
Yoshimasa Saito, Hidetsugu Saito, Hidekazu Suzuki, Takanori Kanai, Division of Gastroenterology, Department of Internal Medicine, Keio University School of Medicine, Shinjuku-ku, Tokyo 160-8582, Japan
Masahiko Nakamura, School of Pharmaceutical Sciences, Kitasato University, Minato-ku, Tokyo 108-8641, Japan
Author contributions: Saito Y and Serizawa H designed the research; Saito Y, Serizawa H, Kato Y and Nakano M performed the clinical research; Nakamura M, Saito H, Suzuki H and Kanai T supervised the research; Saito Y and Serizawa H analyzed the data and wrote the paper.
Supported by Research Grant of Kitasato Institute Hospital.
Institutional review board statement: The study was reviewed and approved by the institutional review board of the Kitasato Institute Hospital.
Clinical trial registration statement: This study was registered with the UMIN Clinical Trials Registry, No. UMIN000009642.
Informed consent statement: All study participants provided informed written consent prior to study enrollment.
Conflict-of-interest statement: None of the authors have any conflicts of interest to declare.
Data sharing statement: No additional data are available.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Yoshimasa Saito, MD, PhD, Division of Pharmacotherapeutics, Keio University Faculty of Pharmacy, 1-5-30 Shibakoen, Minato-ku, Tokyo 105-8512, Japan. saito-ys@pha.keio.ac.jp
Telephone: +81-3-54002692 Fax: +81-3-54002692
Received: June 3, 2015
Peer-review started: June 3, 2015
First decision: August 26, 2015
Revised: September 3, 2015
Accepted: October 17, 2015
Article in press: October 20, 2015
Published online: December 28, 2015

Abstract

AIM: To evaluate the effect of first line esomeprazole (EPZ)-based triple therapy on Helicobacter pylori (H. pylori) eradication.

METHODS: A total of 80 Japanese patients with gastritis who were diagnosed as positive for H. pylori infection by endoscopic biopsy-based or 13C-urea breath tests were included in this study. The average age of the patients was 57.2 years (male/female, 42/38). These patients were treated by first-line eradication therapy with EPZ 40 mg/d, amoxicillin 1500 mg/d, and clarithromycin 400 mg/d for 7 d. All drugs were given twice per day. Correlations between H. pylori eradication, CYP2C19 genotype, and serum pepsinogen (PG) level were analyzed. This study was registered with the UMIN Clinical Trials Registry (UMIN000009642).

RESULTS: The H. pylori eradication rates by EPZ-based triple therapy evaluated by intention-to-treat and per protocol were 67.5% and 68.4%, respectively, which were similar to triple therapies with other first-generation proton pump inhibitors (PPIs). The eradication rates in three different CYP2C19 genotypes, described as extensive metabolizer (EM), intermediate metabolizer, and poor metabolizer, were 52.2%, 72.1%, and 84.6%, respectively. The H. pylori eradication rate was significantly lower in EM than non-EM (P < 0.05). The serum PG I level and PG I/II ratio were significantly increased after eradication of H. pylori (P < 0.01), suggesting that gastric atrophy was improved by H. pylori eradication. Thus, first-line eradication by EPZ-based triple therapy for patients with H. pylori-positive gastritis was influenced by CYP2C19 genotype, and the eradication rate was on the same level with other first-generation PPIs in the Japanese population.

CONCLUSION: The results from this study suggest that there is no advantage to EPZ-based triple therapy on H. pylori eradication compared to other first-generation PPIs.

Key Words: CYP2C19, Esomeprazole, Helicobacter pylori, Pepsinogen, Proton pump inhibitor

Core tip: Esomeprazole (EPZ) is considered to be more effective for inhibition of gastric acid secretion than other first-generation proton pump inhibitors (PPIs) because its metabolism is not influenced by CYP2C19 genotype. In the present study, however, first-line eradication by EPZ-based triple therapy for patients with Helicobacter pylori (H. pylori)-positive gastritis was influenced by CYP2C19 genotype, and the eradication rate was on the same level with triple therapies with other first-generation PPIs in the Japanese population. Unlike previous studies, our results suggest that there is no advantage for EPZ-based triple therapy on H. pylori eradication in comparison with other first-generation PPIs.



INTRODUCTION

Helicobacter pylori (H. pylori) is one of the most prevalent bacterial pathogens and is associated with upper gastrointestinal disorders, such as gastritis, peptic ulcers, functional dyspepsia, gastric mucosa-associated lymphoid tissue lymphoma, and gastric cancer[1-3]. Eradication of H. pylori infection is reported to be an effective approach to curing or preventing these H. pylori-associated diseases[4,5]. One-week of triple therapy with a proton pump inhibitor (PPI), amoxicillin (AMPC), and clarithromycin (CAM) is recommended as first-line H. pylori eradication therapy and covered under the national health insurance system in Japan. However, the eradication rates for H. pylori have declined to approximately 70%[6].

The use of PPIs combined with antibiotics in H. pylori eradication therapy has been demonstrated to not only protect the stomach, but also increase the eradication rate. As antibiotics are more stable in higher pH gastric environments, strong gastric acid inhibition increases the efficacy of H. pylori eradication. The metabolism of first-generation PPIs such as omeprazole (OPZ) is influenced by genetic polymorphism of CYP2C19[7]. Based on the wild-type allele (*1) and the two mutated alleles (*2 and *3) of the CYP2C19 gene, patients can be categorized into three groups: extensive metabolizer (EM; *1/*1), intermediate metabolizer (IM; *1/*2 or *1/*3), and poor metabolizer (PM; *2/*2, *2/*3, or *3/*3). As EM metabolizes OPZ rapidly, the success rate of H. pylori eradication by OPZ-based therapy in EM is lower than that of PM[7-9].

Esomeprazole (EPZ), the S-isomer of OPZ, is the most recent member of the PPI family and is a more potent acid inhibitor than other first-generation PPIs[10,11]. The metabolism of EPZ is considered to be unaffected by CYP2C19 genotype. Indeed, recent studies have reported that there were no significant differences in H. pylori eradication by EPZ-based therapy among EM, IM, and PM of the CYP2C19 genotype, and that EPZ showed better overall H. pylori eradication rates than first-generation PPIs[9,12-14]. However, Nishida et al[15] demonstrated that the H. pylori eradication rate of EPZ-based triple therapy was lower than lansoprazole (LPZ) in the Japanese population. Thus, the effect of H. pylori eradication by EPZ-based therapy is controversial. To evaluate the effect of first line EPZ-based triple therapy on H. pylori eradication, we investigated eradication rate, CYP2C19 genotype, and serum pepsinogen (PG) level in Japanese patients with H. pylori-positive gastritis.

MATERIALS AND METHODS
Patients and study design

A total of 80 Japanese patients with gastritis who were diagnosed as positive for H. pylori infection by a 13C-urea breath test (UBT) or endoscopic biopsy-based test (i.e., histologic examination and H. pylori culture) were included in this study. Patients were recruited between January and September 2013 at the Kitasato Institute Hospital (Tokyo, Japan). The average age of the patients was 57.2 years (male/female, 42/38).

These patients were treated by first-line eradication therapy with EPZ 40 mg/d, AMPC 1500 mg/d, and CAM 400 mg/d for 7 d. All drugs were given twice per day. Three months after eradication, H. pylori infection was validated by UBT. Correlations between H. pylori eradication, CYP2C19 genotype, and serum PG level were analyzed. The study was approved by the ethics committee of the Kitasato Institute Hospital, and written informed consent was obtained from all patients prior to examinations. This study was registered with the UMIN Clinical Trials Registry, number UMIN000009642.

CYP2C19 genotyping

Blood samples were collected from the patients before eradication therapy. The CYP2C19 genotyping for wild-type allele (*1) and two mutated alleles (*2 and *3) was conducted by SRL (Tokyo, Japan). The patients were categorized into three groups based on the CYP2C19 genotype, EM (*1/*1), IM (*1/*2 or *1/*3), and PM (*2/*2, *2/*3, or *3/*3).

Serum PG level

Serum PG I and II levels were measured before and after eradication therapy. Gastric atrophy was evaluated as described previously[16,17]: (-), PG I ≥ 70 ng/mL and PG I/PG II ratio ≥ 3.0; (1+), PGI < 70 ng/mL and PG I/PG II ratio < 3.0; (2+), PG I < 50 ng/mL and PG I/PG II ratio < 3.0; (3+), PG I < 30 ng/mL and PG I/PG II ratio < 2.0.

Statistical analysis

Data were analyzed using the SPSS statistics version 22 software package (IBM Corp., Armonk, NY, United States). The data were also analyzed using χ2 test and multiple logistic regression analysis. H. pylori eradication rate was evaluated by intention-to-treat (ITT) and per protocol (PP). Differences at P < 0.05 were considered significant.

RESULTS
Influence of CYP2C19 genotype on H. pylori eradication by EPZ-based triple therapy

Among 80 patients who were treated by first-line eradication therapy with EPZ, AMPC, and CAM, one patient did not return for a UBT after the therapy. The H. pylori eradication rates of this first-line therapy evaluated by ITT and PP were 67.5% and 68.4%, respectively, which were similar to first-line therapy with LPZ, AMPC, and CAM (67.5%) in the Kitasato Institute Hospital. The results of CYP2C19 genotype and serum PG level in association with H. pylori eradication are shown in Tables 1, 2, 3. The eradication rates of first-line therapy with EPZ in the three CYP2C19 genotypes, EM, IM, and PM, were 52.2% (12/23), 72.1% (31/43), and 84.6% (11/13), respectively. The H. pylori eradication rate of EM was significantly lower than that of non-EM (P = 0.048).

Table 1 Serum pepsinogen level and Helicobacter pylori eradication in the extensive metabolizer group (CYP2C19 genotype: *1/*1).
CaseAgeSexPGI/II
UBTEradication
Before eradicationAfter eradication
E145F3.6-5.0-0.1
E239M3.3-6.7-0.4
E359M3.1-5.2-0.5
E458M2.9-7.1-0.4
E550F2.21+5.1-0.3
E643F2.21+4.9-0.3
E763F1.61+4.1-0.0
E856F2.82+4.1-0.3
E936F2.22+4.6-0.0
E1075F2.52+4.8-0.9
E1167M3.7-2.22+0.0
E1264M0.83+2.22+1.3
E1348M3.4-3.1-12.7×
E1450F4.3-6.4-12.7×
E1567M3.5-3.7-41.6×
E1634F3.0-3.4-19.5×
E1763M3.1-3.0-26.8×
E1871F1.23+3.1-11.0×
E1955M2.41+2.61+24.6×
E2056M2.02+2.21+24.9×
E2180M1.72+1.82+20.9×
E2253M2.22+2.22+26.6×
E2343F2.22+2.32+11.5×
Table 2 Serum pepsinogen level and Helicobacter pylori eradication in the intermediate metabolizer group (CYP2C19 genotype: *1/*2, *1/*3).
CaseAgeSexCYP2C19 genotypePGI/II
UBTEradication
Before eradicationAfter eradication
I161F*1/*22.6-4.5-1.1
I266M*1/*23.6-6.0-0.0
I365F*1/*22.5-4.1-0.2
I471F*1/*23.5-7.4-0.9
I559M*1/*32.2-5.3-1.1
I662M*1/*33.3-8.3-0.0
I767M*1/*24.9-5.0-0.3
I864F*1/*22.8-5.2-0.5
I964F*1/*23.2-5.4-0.1
I1034M*1/*23.1-6.9-0.3
I1152M*1/*23.7-4.9-0.8
I1264M*1/*23.6-4.5-0.2
I1355M*1/*32.0-4.7-1.1
I1458M*1/*23.8-9.4-0.6
I1566F*1/*31.4-3.7-1.0
I1647M*1/*24.0-5.4-0.0
I1742M*1/*32.81+5.3-0.4
I1853M*1/*22.31+3.7-0.8
I1956M*1/*32.01+4.0-2.4
I2051F*1/*21.11+3.3-0.0
I2162F*1/*22.31+4.1-0.3
I2239F*1/*22.72+6.0-0.4
I2363F*1/*32.12+4.0-0.1
I2453F*1/*22.32+4.1-0.3
I2545M*1/*22.42+4.9-0.6
I2655M*1/*22.62+4.2-0.5
I2750M*1/*21.82+3.9-0.6
I2855M*1/*21.33+3.6-0.0
I2953F*1/*21.72+2.92+0.4
I3064M*1/*21.23+2.52+1.5
I3166F*1/*20.83+0.83+1.4
I3253M*1/*34.1-4.5-49.8×
I3361M*1/*24.2-3.2-24.8×
I3444F*1/*23.2-3.2-44.5×
I3551F*1/*22.42+3.1-21.7×
I3628F*1/*32.2-2.21+43.6×
I3770M*1/*32.71+2.71+9.3×
I3870F*1/*22.51+2.01+39.2×
I3965M*1/*33.1-3.02+28.0×
I4045F*1/*32.8-2.52+13.0×
I4178F*1/*20.83+1.43+4.1×
I4245F*1/*21.53+1.63+17.0×
I4370M*1/*31.13+1.13+37.4×
Table 3 Serum pepsinogen level and Helicobacter pylori eradication in the poor metabolizer group (CYP2C19 genotype: *2/*2, *2/*3, *3/*3).
CaseAgeSexCYP2C19 genotypePGI/II
UBTEradication
Before eradicationAfter eradication
P164F*2/*23.6-5.8-0.2
P246M*2/*24.0-5.5-1.2
P364F*2/*22.21+3.8-1.1
P463F*2/*22.12+3.9-0.0
P562F*2/*32.32+4.2-0.2
P664M*2/*32.22+5.0-0.0
P763M*2/*22.72+4.9-1.2
P877F*3/*31.73+2.92+0.1
P968M*2/*21.32+1.93+1.2
P1060M*2/*20.63+1.43+0.8
P1157M*2/*24.1-NDND0.2
P1265F*2/*22.01+2.01+30.2×
P1338F*2/*22.32+2.51+63.8×
Influence of PG level on H. pylori eradication by EPZ-based triple therapy

In addition to H. pylori infection, serum PG level is associated with gastric mucosal atrophy and gastric cancer risk, which is used for gastric cancer screening[17-19]. Serum PG I level and PG I/II ratio in association with H. pylori eradication are shown in Tables 1, 2, and 3. Table 4 is a summary of PG I/II ratio and H. pylori eradication. Serum PG I level and PG I/II ratio were significantly increased after eradication of H. pylori (P = 0.007), suggesting that gastric atrophy was improved by H. pylori eradication therapy. We performed a multiple logistic regression analysis to identify independent predictors associated with H. pylori eradication. As shown in Table 5, only CYP2C19 genotype was statistically significant as an independent predictor associated with H. pylori eradication.

Table 4 Correlation between pepsinogen I/II ratio and Helicobacter pylori eradication.
EradicationPGI/II ratio
Total
IncreaseNo changeDecrease
Success2626153
Failure418325
Total3044478
Table 5 Multiple logistic regression analysis to identify independent predictors associated with Helicobacter pylori eradication.
VariableP value
CYP2C19 genotype (EM vs non-EM)0.048
Age0.603
Sex0.637
Pepsinogen I/II before eradication0.809
DISCUSSION

EPZ is a second-generation PPI that is broadly used for the treatment of acid-peptic diseases. It is believed that EPZ is more effective for inhibition of gastric acid secretion than other first-generation PPIs, because it is the S-isomer of OPZ and its metabolism is not affected by CYP2C19 genotype. Recent studies have also shown that H. pylori eradication by EPZ-based therapy is not influenced by CYP2C19 genotype, and that overall H. pylori eradication rates of EPZ-based therapy was better than first-generation PPIs[9,12-14]. On the other hand, Hunfeld et al[11] revealed that the acid-inhibitory effect of EPZ was influenced by CYP2C19 genotype. Nishida et al[15] demonstrated that the H. pylori eradication rate of EPZ-based triple therapy was lower than LPZ in the Japanese population. Thus, the effect of EPZ-based therapy on H. pylori eradication is controversial.

In this study we evaluated the influence of CYP2C19 genotype in patients with H. pylori-positive gastritis treated by EPZ-based triple therapy. Our results demonstrated that the H. pylori eradication rate was significantly lower in EM phenotype patients having the wild-type CYP2C19 genotype, compared to the non-EM patients with at least one mutant allele (*2 and *3). The result of multiple logistic regression analysis also showed that CYP2C19 genotype is an independent predictor associated with H. pylori eradication. These findings suggest that EM metabolizes EPZ more rapidly, and therefore plasma concentrations of EPZ become lower, resulting in a lower H. pylori eradication rate than that of non-EM. Nishida et al[15] conducted a multicenter, randomized, open-label, non-inferiority trial comparing EPZ and LPZ in triple therapy for H. pylori eradication in Japan. They reported that the H. pylori eradication rates of EPZ-based triple therapy (69.4%/76.9%, ITT/PP) were lower than LPZ-based triple therapy (73.9%/79.8%, ITT/PP). In this study, the overall H. pylori eradication rates of EPZ-based triple therapy were 67.5%/68.4% (ITT/PP), which were similar to the previous report. A recent study with a Japanese population has also shown that the H. pylori eradication rates by the regimen with rabeprazole, AMPC, and CAM were 73.3%/77.2% (ITT/PP)[6]. Thus, these findings indicate that the H. pylori eradication rate by EPZ-based triple therapy is at the same level with triple therapies with other first-generation PPIs.

Serum PG level is associated with gastric mucosal atrophy and gastric cancer risk[17-19]. In the present study, the serum PG I level and PG I/II ratio were significantly increased after eradication of H. pylori, suggesting that gastric atrophy was improved by H. pylori eradication. Serum PG level and PG I/II ratio can be noninvasive biomarkers for screening of gastric atrophy and gastric cancer. H. pylori eradication has clinical benefit for improvement of gastric mucosal atrophy and prevention against gastric cancer.

In conclusion, first-line H. pylori eradication by EPZ-based triple therapy was influenced by CYP2C19 genotype, and the overall eradication rate was on the same level with triple therapies with other first-generation PPIs in Japanese patients with H. pylori-positive gastritis. Unlike previous reports, the results in this study suggest that there is no advantage to EPZ-based triple therapy on H. pylori eradication in comparison to other first-generation PPIs. Further studies are needed in a large population of patients in different countries before an accurate correlation between the EPZ-based therapy and CYP2C19 genotype is completed. Evaluation of CYP2C19 genotype and serum PG level is important to develop more effective personalized H. pylori eradication therapy with EPZ.

COMMENTS
Background

Esomeprazole (EPZ) is a second-generation proton pump inhibitor (PPI) that is broadly used for the treatment of acid-peptic diseases. Recent studies have shown that EPZ is more effective for inhibition of gastric acid secretion than other first-generation PPIs because its metabolism is not influenced by CYP2C19 genotype. However, the effect of Helicobacter pylori (H. pylori) eradication by EPZ-based therapy is controversial.

Research frontiers

First-line eradication by EPZ-based triple therapy for patients with H. pylori-positive gastritis was influenced by CYP2C19 genotype, and the eradication rate was at the same level found with other first-generation PPIs in the Japanese population.

Innovations and breakthroughs

Unlike previous reports, the results in this study suggest that there is no advantage to EPZ-based triple therapy on H. pylori eradication in comparison to other first-generation PPIs.

Applications

Evaluation of CYP2C19 genotype and serum pepsinogen level is important to develop more effective personalized H. pylori eradication therapy with EPZ.

Terminology

EPZ is the most recent member of the PPI family and is a more potent acid inhibitor than other first-generation PPIs. The metabolism of first-generation PPIs is influenced by genetic polymorphism of CYP2C19. Based on CYP2C19 genotype, patients can be categorized into three groups: extensive metabolizer, intermediate metabolizer, and poor metabolizer.

Peer-review

This study reports that the second-generation PPI inhibitor, EPZ, has no apparent advantage over triple therapies utilizing other first-generation PPIs for overall eradication of H. pylori in patients with gastritis. The EPZ-based therapy was influenced by the CYP2C19 genotype of the studied Japanese patients.

Footnotes

P- Reviewer: Li SD, Slomiany BL S- Editor: Gong ZM L- Editor: Filipodia E- Editor: Zhang DN

References
1.  Suzuki H, Hibi T, Marshall BJ. Helicobacter pylori: present status and future prospects in Japan. J Gastroenterol. 2007;42:1-15.  [PubMed]  [DOI]
2.  Cover TL, Blaser MJ. Helicobacter pylori in health and disease. Gastroenterology. 2009;136:1863-1873.  [PubMed]  [DOI]
3.  Suzuki H, Moayyedi P. Helicobacter pylori infection in functional dyspepsia. Nat Rev Gastroenterol Hepatol. 2013;10:168-174.  [PubMed]  [DOI]
4.  Fukase K, Kato M, Kikuchi S, Inoue K, Uemura N, Okamoto S, Terao S, Amagai K, Hayashi S, Asaka M. Effect of eradication of Helicobacter pylori on incidence of metachronous gastric carcinoma after endoscopic resection of early gastric cancer: an open-label, randomised controlled trial. Lancet. 2008;372:392-397.  [PubMed]  [DOI]
5.  Suzuki H, Nishizawa T, Hibi T. Helicobacter pylori eradication therapy. Future Microbiol. 2010;5:639-648.  [PubMed]  [DOI]
6.  Nishizawa T, Maekawa T, Watanabe N, Harada N, Hosoda Y, Yoshinaga M, Yoshio T, Ohta H, Inoue S, Toyokawa T. Clarithromycin Versus Metronidazole as First-line Helicobacter pylori Eradication: A Multicenter, Prospective, Randomized Controlled Study in Japan. J Clin Gastroenterol. 2015;49:468-471.  [PubMed]  [DOI]
7.  Tang HL, Li Y, Hu YF, Xie HG, Zhai SD. 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. PLoS One. 2013;8:e62162.  [PubMed]  [DOI]
8.  Furuta T, Ohashi K, Kamata T, Takashima M, Kosuge K, Kawasaki T, Hanai H, Kubota T, Ishizaki T, Kaneko E. Effect of genetic differences in omeprazole metabolism on cure rates for Helicobacter pylori infection and peptic ulcer. Ann Intern Med. 1998;129:1027-1030.  [PubMed]  [DOI]
9.  McNicholl AG, Linares PM, Nyssen OP, Calvet X, Gisbert JP. Meta-analysis: esomeprazole or rabeprazole vs. first-generation pump inhibitors in the treatment of Helicobacter pylori infection. Aliment Pharmacol Ther. 2012;36:414-425.  [PubMed]  [DOI]
10.  Kendall MJ. Review article: esomeprazole--the first proton pump inhibitor to be developed as an isomer. Aliment Pharmacol Ther. 2003;17 Suppl 1:1-4.  [PubMed]  [DOI]
11.  Hunfeld NG, Touw DJ, Mathot RA, van Schaik RH, Kuipers EJ. A comparison of the acid-inhibitory effects of esomeprazole and rabeprazole in relation to pharmacokinetics and CYP2C19 polymorphism. Aliment Pharmacol Ther. 2012;35:810-818.  [PubMed]  [DOI]
12.  Miehlke S, Schneider-Brachert W, Kirsch C, Morgner A, Madisch A, Kuhlisch E, Haferland C, Bästlein E, Jebens C, Zekorn C. One-week once-daily triple therapy with esomeprazole, moxifloxacin, and rifabutin for eradication of persistent Helicobacter pylori resistant to both metronidazole and clarithromycin. Helicobacter. 2008;13:69-74.  [PubMed]  [DOI]
13.  Pan X, Li Y, Qiu Y, Tang Q, Qian B, Yao L, Shi R, Zhang G. Efficacy and tolerability of first-line triple therapy with levofloxacin and amoxicillin plus esomeprazole or rabeprazole for the eradication of Helicobacter pylori infection and the effect of CYP2C19 genotype: a 1-week, randomized, open-label study in Chinese adults. Clin Ther. 2010;32:2003-2011.  [PubMed]  [DOI]
14.  Lee VW, Chau TS, Chan AK, Lee KK, Waye MM, Ling TK, Chan FK. Pharmacogenetics of esomeprazole or rabeprazole-based triple therapy in Helicobacter pylori eradication in Hong Kong non-ulcer dyspepsia Chinese subjects. J Clin Pharm Ther. 2010;35:343-350.  [PubMed]  [DOI]
15.  Nishida T, Tsujii M, Tanimura H, Tsutsui S, Tsuji S, Takeda A, Inoue A, Fukui H, Yoshio T, Kishida O. Comparative study of esomeprazole and lansoprazole in triple therapy for eradication of Helicobacter pylori in Japan. World J Gastroenterol. 2014;20:4362-4369.  [PubMed]  [DOI]
16.  Sugimoto M, Furuta T, Shirai N, Nakamura A, Kajimura M, Sugimura H, Hishida A, Ishizaki T. Poor metabolizer genotype status of CYP2C19 is a risk factor for developing gastric cancer in Japanese patients with Helicobacter pylori infection. Aliment Pharmacol Ther. 2005;22:1033-1040.  [PubMed]  [DOI]
17.  Mizuno S, Kobayashi M, Tomita S, Miki I, Masuda A, Onoyama M, Habu Y, Inokuchi H, Watanabe Y. Validation of the pepsinogen test method for gastric cancer screening using a follow-up study. Gastric Cancer. 2009;12:158-163.  [PubMed]  [DOI]
18.  Miki K, Fujishiro M, Kodashima S, Yahagi N. Long-term results of gastric cancer screening using the serum pepsinogen test method among an asymptomatic middle-aged Japanese population. Dig Endosc. 2009;21:78-81.  [PubMed]  [DOI]
19.  Mizuno S, Miki I, Ishida T, Yoshida M, Onoyama M, Azuma T, Habu Y, Inokuchi H, Ozasa K, Miki K. Prescreening of a high-risk group for gastric cancer by serologically determined Helicobacter pylori infection and atrophic gastritis. Dig Dis Sci. 2010;55:3132-3137.  [PubMed]  [DOI]