Pharmacokinetic–pharmacodynamic analysisof the role of CYP2C19genotypes in short-termrabeprazole-based tripletherapy against HelicobacterpyloriJyh-Chin Yang, Yu-Fan Yang,1 Yow-Shieng Uang,2 Chun-Jung Lin1 &

Teh-Hong Wang

Department of Internal Medicine, Hospital and College of Medicine, 1School of Pharmacy, College of

Medicine, National Taiwan University and 2School of Pharmacy, Taipei Medical University, Taipei,

Taiwan

CorrespondenceDr Chun-Jung Lin, School of Pharmacy,College of Medicine, National TaiwanUniversity, 12F, No. 1, Sec. 1, Jen-Ai Rd,Taipei 100, Taiwan.Tel: + 886 2 2312 3456, ext 88386Fax: + 886 2 2391 9098E-mail: clementumich@ntu.edu.tw----------------------------------------------------------------------

KeywordsCYP2C19 polymorphism, Helicobacterpylori, population PK/PD, rabeprazole----------------------------------------------------------------------

Received1 December 2008

Accepted11 February 2009

WHAT IS ALREADY KNOWN ABOUTTHIS SUBJECT• Asians have a higher percentage of CYP2C19 poor

metabolizers (PMs) and a high percentage ofHelicobacter pylori infection compared with Whites.

• Although rabeprazole has been suggested to beleast affected by CYP2C19 genotype, thepharmacokinetic properties of rabeprazole havebeen shown to correlate with the CYP2C19genotype.

• Short-term (i.e. <7 days) rabeprazole-based tripletherapy has been suggested for its use ineradicating H. pylori, whereas the eradication ratehas been reported variously as 90–27% withoutCYP2C19 genotyping.

WHAT THIS STUDY ADDS• Population pharmacokinetic–pharmacodynamic

analysis showed that the plasma rabeprazole levels,the values of keo (the first-order rate constant fordrug dissipation from the effect compartment), andthe predicted gastrin-time profile were higher inCYP2C19 PMs than in extensive metabolizers (EMs)after multiple dosing.

• Helicobacter pylori was eradicated in all CYP2C19PMs except in one patient infected by a resistantstrain, whereas the eradication rates ranged from 58to 85% in CYP2C19 EMs.

AIMSThe aim was to explore the role of CYP2C19 polymorphism in short-termrabeprazole-based triple therapy against Helicobacter pylori infection.

METHODSPatients with H. pylori infection were tested for CYP2C19 genotype as poormetabolizers (PMs) or extensive metabolizers (EMs, homozygous EM orheterozygous EM) and given rabeprazole for 7 days. Antibiotics (clarithromycinand amoxicillin) were given on days 1–4, days 4–7, or days 1–7. A direct linkmodel with an effect compartment was used in the populationpharmacokinetic–pharmacodynamic analysis. The status of H. pylori infectionwas evaluated.

RESULTSRabeprazole clearance was lower in CYP2C19 PMs than in EMs (with averagevalues of 10.7 vs. 16.8 l h-1 in PMs and EMs, respectively), resulting in higherplasma levels in the former group. The values of EC50 and keo of gastrin responseincreased with multiple doses of rabeprazole. The keo values were lower inCYP2C19 PMs than in EMs on day 1 (0.012 vs. 0.017 ¥ 10-4 l min-1), and higherthan in EMs on day 4 (0.804 vs. 0.169 ¥ 10-4 l min-1) of rabeprazole treatment.The predicted gastrin-time profile showed a higher response in CYP2C19 PMsthan in EMs on days 4 and 7. Helicobacter pylori was eradicated in all CYP2C19PMs except in one patient infected by a resistant strain. In contrast, in CYP2C19EMs the eradication rates ranged from 58 to 85%.

CONCLUSIONSCYP2C19 genotypes play a role in H. pylori eradication therapy.Rabeprazole-based short-term triple therapy may be applicable in CYP2C19 PMsfor H. pylori eradication.

British Journal of ClinicalPharmacology

DOI:10.1111/j.1365-2125.2009.03393.x

Br J Clin Pharmacol / 67:5 / 503–510 / 503© 2009 The AuthorsJournal compilation © 2009 The British Pharmacological Society

Introduction

Helicobacter pylori is closely related to many gastrointes-tinal diseases, including chronic active gastritis, pepticulcers, gastric carcinoma and gastric mucosa-associatedlymphoid tissue lymphoma [1]. Eradication of H. pylori isimportant for reducing the relapse rate of ulcers and risk ofcarcinogenesis. Triple therapy with a proton pump inhibi-tor (PPI) and two antibiotics is considered a standard treat-ment for H. pylori infection.When the drugs are given at therecommended doses, the eradication rates range from 70to 85% for a duration of treatment of 7–14 days [2, 3]. Fewstudies have compared the cost effectiveness of these dif-ferent lengths of treatment [4]. Nonetheless, short-term(i.e. <7 days) triple therapy has been reported to increasepatient compliance and reduce costs and adverse effects[5–7], but the evidence is limited and the rationale needsto be elucidated.

In an acidic environment, PPIs are protonated to formsulphenamides, which are covalently bound with cysteineresidues in the gastric proton pump to inhibit protonsecretion [8]. Most PPIs are mainly metabolized byCYP2C19, which is known to exhibit polymorphism in bothits genotype and phenotype with much higher percentageof poor metabolizers (PMs) in Asians [9, 10]. Among thePPIs, rabeprazole has been demonstrated to have a highdegree of activity against H. pylori. One reason is the higherpKa for the conversion of rabeprazole to the sulphenamide,which means it is converted at a higher pH than other PPIs,resulting in more rapid proton pump inhibition [11]. Fur-thermore, rabeprazole and its thio-ether metabolite inhibitthe motility and urease activity of H. pylori [12, 13]. Giventhe better pharmacological profile of rabeprazole, ashorter regimen has been suggested for its use in eradi-cating H. pylori; however, the findings are controversialand the eradication rate using rabeprazole–amoxicillin–clarithromycin for 3–4 days has been reported variously as90–27% [5]. One reason for the variation in these resultscould be that the CYP2C19 genotypes of the enrolledsubjects were not determined in these studies. Althoughrabeprazole has been suggested to be the PPI leastaffected by CYP2C19 genotype [14], the eradication rate ofa rabeprazole regimen has been shown to correlate withthe CYP2C19 genotype [15]. The pharmacokinetic proper-ties, including the area under the curve (AUC), maximalplasma concentration (Cmax) and clearance (CL) of rabepra-zole were all found to be significant different betweenCYP2C19 PMs and CYP2C19 extensive metabolizers (EMs)[16]. Higher plasma gastrin levels were also observed inCYP2C19 PMs than in EMs after taking rabeprazole 20 mgb.i.d. for 4 days [17]. Since the extent and duration of intra-gastric acid inhibition have been proven to be important inH. pylori eradication and ulcer healing [14, 18], the higherplasma concentrations of rabeprazole and gastrin inCYP2C19 PMs may contribute to a better clinicaloutcome.

In the present study, population pharmacokinetic–pharmacodynamic (PK–PD) analysis was used to explorethe role of CYP2C19 genotype in rabeprazole-based tripletherapy on days 1, 4 and 7 of treatment. In addition, theclinical outcome of H. pylori eradication was evaluated inpatients receiving rabeprazole with different antibioticregimens for 1 week.

Materials and methods

Study designPatients with H. pylori-positive ulcer or gastritis wererecruited at the National Taiwan University Hospital.Patients who met any of the following conditions wereexcluded: (i) pregnant or nursing woman; (ii) serious con-comitant illness; (iii) malignant tumour of any kind; (iv)serious bleeding during the course of this ulcer; (v) previ-ous gastric surgery; and (vi) taking bismuth compounds orPPIs within 30 days prior to pretreatment endoscopy. Ulcerand H. pylori status were evaluated by endoscopy, histol-ogy, culture and the 13C-urea breath test. The study wasapproved by the Ethical Practices Committee of theNational Taiwan University Hospital (Study ID number:920505, NTUH93S060).

These patients were randomly assigned to one of thethree study groups after giving their written informedconsent. Rabeprazole 20 mg twice daily was given orallyfor 7 days to all three groups. Amoxicillin 1 g and clarithro-mycin 500 mg were also given twice daily on days 1–4of rabeprazole treatment (group A), days 4–7 (group B),or days 1–7 (group C). The CYP2C19 genotype of eachparticipant was analysed by the polymerase chainreaction-based restriction fragment length polymorphism(PCR-RFLP) method.

For PK–PD analysis, to avoid the patients having to bepresent all day, they were randomly assigned to one of fourgroups and, on days 1, 4 or 7 of rabeprazole treatment,10-ml aliquots of venous blood were drawn 30 min beforedrug administration and at the time points of 0.5, 2, 4 and8 h (group 1), 0.5, 1, 3 and 6 h (group 2), 1, 3, 6 and 10 h(group 3), or 2, 4, 8 and 10 h (group 4). The blood wascentrifuged at 800 g for 10 min within 15 min of collectionand 200 ml of plasma was taken for gastrin analysis and therest of the sample placed in a storage tube containing350 ml of a 1% aqueous solution of diethylamine forplasma rabeprazole concentration analysis. All sampleswere frozen at -80 °C until analysis.

Endoscopy and biopsyDuring each endoscopic examination, four biopsy speci-mens were obtained from the antrum and four fromthe body for histology, bacterial culture, and theCampylobacter-like organism (CLO) test. Two of the fourpairs of specimens were processed with haematoxylin andeosin and Warthin–Starry silver stain. Another pair was

J-C. Yang et al.

504 / 67:5 / Br J Clin Pharmacol

placed in brain heart infusion broth for transportation,then ground up and streaked onto an agar plate withselective medium [19]. The plates were incubated at 37 °Cunder micro-aerophilic conditions (5% O2, 10% CO2, 85%N2) for 3–7 days. Helicobacter pylori was identified by itscharacteristic biotyping as Gram-negative, but oxidase-,catalase- and urease-positive.The fourth pair of specimenswas tested using a CLO test kit (Delta West Pty Ltd., Bentley,Western Australia), the colour of which changes fromyellow to purple if H. pylori is present.

Evaluation of H. pylori status and antibioticresistanceHelicobacter pylori status was considered positive when (i)at least two of the above three tests were positive or (ii)only the bacterial culture test was positive. The E-test (ABBiodisk, Solna, Sweden) was used to evaluate the amoxi-cillin and clarithromycin resistance of H. pylori, whichwas considered to be resistant to antibiotics when theminimum inhibitory concentration value was �1 mg L-1

[19]. Helicobacter pylori eradication was evaluated using a13C-urea breath test before,and at 4–6 weeks after, rabepra-zole treatment, performed as described previously [17].

CYP2C19 genotypingDNA was isolated from peripheral leucocytes in bloodsamples by a standard method [20]. Genetic polymor-phism of the CYP2C19*2 (CYP2C19 m1) and CYP2C19*3(CYP2C19 m2) alleles was identified by PCR-RFLP asdescribed previously [21, 22]. Patients were identified ashomozygous extensive metabolizers (HomEM; wt/wt),heterozygous extensive metabolizers (HetEM; wt/m1 orwt/m2) or poor metabolizers (PM; m1/m1 or m1/m2)according to CYP2C19 genotypes.

Determination of plasma concentrations ofrabeprazole and gastrinPlasma concentrations of rabeprazole were determinedby high-performance liquid chromatography as describedpreviously [23]. Plasma gastrin concentrations were deter-mined by radioimmunoassay using ICN kits (ICN Phar-maceuticals, Costa Mesa, CA, USA) according to themanufacturer’s protocol, as in a previous study [17].

Population PK–PD analysisPopulation PK–PD analysis was performed using theNONMEM program (version V, level 1.1).To establish the PKand PD models, the data were analysed according to theday of rabeprazole treatment (i.e. pooled data for day 1,day 4, or day 7) given that the dosing of antibiotics is irrel-evant to the PK–PD properties of rabeprazole. A naive-pooled data analysis (i.e. pool data for all subjects and fitsingle ‘naive’ individual) was performed to obtain the initialvalues for population PK–PD analysis. PK properties wereestimated before the link to PD analysis. For PK analysis,first-order conditional estimation and a PREDPP subrou-

tine, ADVAN2, were used for a one-compartment modelwith first-order absorption (ka) and a lag time (Alag). For PDanalysis, a first-order method and a PREDPP subroutine,ADVAN6, were used after the estimation of the PK param-eters. On the basis of the counterclockwise hysteresis loopobserved in the concentration–effect profile of rabepra-zole [17], a direct link model with an effect compartmentwas used [24]. The concentration in the effect compart-ment (Ce) is described by Equation 1:

Ck k D

V

e

k k k k

e

k k k ke

eeo a

d

kt

eo a

k t

eo a ak t

a

eo

=−( ) −( )

+−( ) −( )

⎡⎣⎢

+

− −

−

kk k k ka eo eo−( ) −( )⎤⎦⎥

(1)

where keo is the first-order rate constant for drug dissipa-tion from the effect compartment, ka the absorption con-stant, Vd the volume of distribution, and D the dose ofrabeprazole. The PD response is described by Equation 2:

E EE E C

EC Cm e

e

= +−( ) ×

+00

50

γ

γ γ (2)

where E is the gastrin levels after dosing, E0 the baselinegastrin levels, Em the maximal gastrin levels, EC50 therabeprazole concentration to produce half Em, and g theslope factor of the concentration–response curve.The baseand final models for the PK and PD analysis are listed inTable 1, in which q represents the predicted populationmean of the parameters, h the random effect with a meanof zero and a variance of w2, and BSA the body surface areaestimated using Mosteller’s formula [25].

Statistical analysisThe equivalence of demographic information amongvarious treatment groups or genotypes was revealed by c2

Table 1Parameters used in the population pharmacokinetic–pharmacodynamic(PK–PD) analysis for rabeprazole*

Base PK model Final PK model

V ed vdVd= ×θ η V e ed v

BSAd

BSA Vd= × ××θ θ η

CL eCLCL= ×θ η CL e eCL GT

BSABSA CL CL= × × ××θ θ θ η,

k ea kaka= ×θ η k ea ka

ka= ×θ η

A elag AlagAlag= ×θ η A elag Alag

Alag= ×θ η

Base PD model Final PD model

E em EmEm= ×θ η E em Em

Em= ×θ η

E eEE

0 00= ×θ η E eE

E0 0

0= ×θ η

EC eECEC

50 5050= ×θ η EC eEC

EC50 50

50= ×θ η

k eeo keokeo= ×θ η k eeo k GTeo

keo= × ×θ θ η

γ θγηγ= × e γ θγ

ηγ= × e

*Vd, volume of distribution; CL, clearance; ka, absorption constant; Alag, absorp-tion lagged time; Em, maximal effect; E0, baseline effect; EC50, concentration whenhalf Em achieved; keo, elimination constant for the effect compartment; BSA, bodysurface area; g, slope; GT, CYP2C19 genotype; qx, population mean of parameterx; hx, intersubject variability of parameter x.

CYP2C19 genotypes in short-term triple therapy

Br J Clin Pharmacol / 67:5 / 505

independence test or t-test or ANOVA. The comparisons ofpredicted PK–PD parameters among various days or geno-types were analysed by the two-sided t-test or ANOVA. Fish-er’s exact test or the c2 test was used to analyse clinicaloutcome, only those subjects who completed the studybeing included in the analysis. A P-value < 0.05 was consid-ered to be statistically significant.

Results

Subject characteristicsForty-eight subjects, 33 men and 15 women, aged 18–74years were enrolled and assigned randomly to one of thethree study groups A, B and C (antibiotics on days 1–4, 4–7,or 1–7, respectively) (Table 2). Nine cases were CYP2C19PMs and 39 EMs (including 18 HomEM and 21 HetEM). Theprevalence rates of CYP2C19 HomEM, HetEM and PM wereabout 38, 44 and 18%, respectively. One subject with EMgenotype in group B was excluded from the PK–PD analy-sis due to the lack of a blood sample. One subject with EMgenotype in group C was excluded from the clinicaloutcome estimation because she failed to attend for theafter-treatment 13C-urea breath test evaluation.

The c2 independence tests revealed that the genderstructure and genotype structure were not significantlydifferent among three study groups, with P-values of 0.418and 0.605, respectively. The gender structure was notsignificantly different (P-value = 0.285) between PM andEM groups. The two-way ANOVA showed that the meansof age were not significantly different among threegroups (P-value = 0.424) or between two genotypes(P-value = 0.962), and no significant differences onthe interaction of study groups and genotypes(P-value = 0.370).There was no significant difference in thedemographic data for the patients categorized by treat-ment group (Table 2) or CYP2C19 genotype (except theage between HomEM and HetEM on day 7) or rabeprazoletreatment day (Table 3).

Population PK–PD analysisIn the PK analysis (Table 4), addition of the CYP2C19 geno-type and the BSA of the subjects improved the fit com-pared with the base model, and these were thereforeincluded in the final PK model.For the PK parameters, therewas no difference among the different sampling days insubjects with the same CYP2C19 genotype (Table 4). Thetotal clearance of rabeprazole in CYP2C19 PMs was signifi-

Table 2Demographic data for the patients on the different treatment protocols (groups A, B, and C)*

A B C

No. 16 16 16CYP2C19 (HomEM/HetEM/PM) 5/8/3 5/7/4 8/6/2

Age (years) 53.5 (26–73) 47.6 (18–72) 53.3 (37–74)Gender (% M/F) 62.5/37.5 81.3/18.8 62.5/37.5

Height (cm) 165.3 (158–180) 166.5 (156–176) 165.2 (155–174)Weight (kg) 63.1 (49–81) 65.2 (49–85) 63.3 (49–77)

BSA (m2) 1.70 (1.47–1.94) 1.73 (1.48–2.00) 1.70 (1.50–1.86)

*Rabeprazole treatment from day 1 to day 7, antibiotics (amoxicillin and clarithromycin) being given on days 1–4 (group A), days 4–7 (group B), or days 1–7 (group C). The valuesin parentheses indicate the data range. HomEM, homozygous extensive metabolizers; HetEM, heterozygous extensive metabolizers; PM, poor metabolizers; BSA, body surface area.

Table 3Demographic data for the patients categorized according to rabeprazole treatment day

Day 1 Day 4 Day 7CYP2C19 HomEM HetEM PM HomEM HetEM PM HomEM HetEM PM

No. 13 14 5 10 15 7 13 13 6Age (years) 55.7 51.6 52.4 54.9 46.1 53.9 57.2 44.5* 48.8

(26–74) (37–65) (44–62) (26–73) (18–65) (37–72) (44–74) (18–60) (37–72)

Gender (% M/F) 69/31 64/36 40/60 80/20 73/27 57/43 69/31 77/23 67/33Height (cm) 165.4 165.3 165.0 166.7 165.7 165.4 164.1 167.7 165.8

(155–180) (156–177.5) (160–169) (157–180) (156–177.5) (160–170) (155–172.5) (156–176) (160–170)

Weight (kg) 65.2 63.2 58.2 66.2 63.1 63.4 65.0 64.9 61.2(55–77.1) (49–81) (49.1–62) (52–77.1) (49–81) (49–85) (52–77) (52–74) (49–85)

BSA (m2) 1.73 1.70 1.63 1.75 1.70 1.70 1.72 1.74 1.67(1.55–1.94) (1.47–1.90) (1.50–1.71) (1.51–1.94) (1.47–1.90) (1.48–2.00) (1.51–1.89) (1.50–1.87) (1.48–2.00)

*P < 0.05, day 7 HomEM vs. HetEM. The values in parentheses indicate the data range. HomEM, homozygous extensive metabolizers; HetEM, heterozygous extensive metabolizers;PM, poor metabolizers; BSA, body surface area.

J-C. Yang et al.

506 / 67:5 / Br J Clin Pharmacol

cantly lower than that in CYP2C19 EMs on days 1, 4 and 7 oftreatment (P < 0.05). In all treatment days, the averagevalues of rabeprazole clearance were 10.7 and 16.8 l h-1 inPMs and all EMs, respectively. The clearance estimated inHomEM was not different from that in HetEM. The volumeof distribution (Vd) and the absorption rate constant (ka)were comparable between patients with the differentCYP2C19 genotypes. Accordingly, higher plasma rabepra-zole concentrations were observed in CYP2C19 PMsthan in EMs after either a single dose (i.e. day 1) ormultiple doses (i.e. day 4 and day 7) of rabeprazoletreatment.

The baseline serum gastrin levels were 37.1 � 35.4,29.0 � 22.9 and 20.8 � 21.9 pg ml-1, respectively, forHomEM, HetEM and PM (P = 0.717). Since HomEM andHetEM did not differ in their PK properties, they are pooledas EM (compared with PM) for further PD analysis (Table 5).As a result, the maximal effect (Emax) was decreased and theEC50 increased after multiple doses of rabeprazole, indicat-ing that a higher rabeprazole concentration may berequired to achieve the same effect after multiple doses.The mean estimated keo value from the effect compart-ment also increased with multiple doses. It was noted thatthe keo value was lower in CYP2C19 PMs than in EMs on day1, and higher than in EMs on day 4 of rabeprazole treat-ment. A higher keo value indicates a shorter delay beforethe rabeprazole-induced gastrin response. When thegastrin response of rabeprazole was predicted accordingto Equation 2 as a function of time, CYP2C19 PMs showeda better response than EMs on days 4 and 7,and the gastrinconcentration increased after multiple doses of rabepra-zole (Figure 1).

Clinical outcome (H. pylori eradication)Forty-seven subjects completed the evaluation of eradi-cation. Of these, H. pylori infection was successfully eradi-ated in 36 (Table 6). The sensitivity of H. pylori to

clarithromycin played an important role in the eradica-tion rate. Subjects infected by clarithromycin-sensitive H.pylori had significantly higher eradication rates thanthose infected by clarithromycin-resistant H. pylori (83.3%vs. 20%, P = 0.008; all sampling days combined). There wasno significant difference in eradication rate among thedifferent treatment groups, even after stratification forclarithromycin sensitivity (Table 6). However, we doobserve the decreasing P-value (P-value decrease from0.491 to 0.108) for the testing of equal eradication ratesamong three treatment groups when we consideredclarithromycin sensitivity only. It was also noted thatH. pylori infection was successfully eradicated in allCYP2C19 PMs, independent of the regimen, except in onepatient infected by a resistant strain. In contrast, the eradi-cation rate ranged from 71 to 80% in HomEM and from43 to 100% in HetEM, depending on the treatments. No

Table 4Estimated pharmacokinetic parameters for the patients categorized by rabeprazole treatment day

Day 1 Day 4 Day 7HomEM HetEM All EM PM HomEM HetEM All EM PM HomEM HetEM All EM PM

CL (l h-1) 16.8* 14.8* 15.8* 9.75 18.6* 17.7* 18.0* 12.6 17.8 15.7 16.7* 9.87

SD 2.61 3.39 3.15 2.96 4.04 3.99 3.94 3.20 8.52 5.39 6.99 2.05K (1 h-1) 0.72 0.63 0.68 0.50 0.69* 0.72* 0.71* 0.53 0.75 0.67 0.71* 0.49SD 0.16 0.18 0.17 0.25 0.07 0.07 0.07 0.08 0.32 0.14 0.25 0.08

V (l) 24.7 25.1 22.7

SD 10.1 4.71 3.82Ka (1/h) 2.26 1.91 3.55SD 1.76 0.88 6.40

Alag (h) 1.33 1.71 1.44

SD 0.27 0.86 0.30

*Significant difference (P < 0.05) from PM. HomEM, homozygous extensive metabolizers; HetEM, heterozygous extensive metabolizers; EM, extensive metabolizers; PM, poormetabolizers.

Table 5Estimated pharmacodynamic parameters for the patients categorized byrabeprazole treatment day

Day 1 Day 4 Day 7All EM PM All EM PM All EM PM

E0 42.3 40.3 42.6

(pg ml-1) (23.6) (55.7) (6.3)Emax 293.4‡ 289.8§ 252.5‡§(pg ml-1) (104.0) (1.8) (3.5)

EC50 0.2†‡ 56.0†§ 34.8‡§

(ng ml-1) (0.1) (2.4) (1.3)Keo ¥ 104 0.017*†‡ 0.012* 0.169*†§ 0.804* 7.975‡§ 9.412(l min-1) (0.001) (0.002) (0.019) (0.104) (18.667) (16.055)

g 2.0003†‡ 0.2603†§ 0.4478‡§

(0.0006) (0.00001) (0.0098)

*P < 0.05 between all EMs and PMs on day 1 and day 4. †P < 0.05 between day1 and day 4. ‡P < 0.05 between day 1 and day 7. §P < 0.05 between day 4 andday 7. The values in parentheses indicate the standard deviation. EM, extensivemetabolizers; PM, poor metabolizers.

CYP2C19 genotypes in short-term triple therapy

Br J Clin Pharmacol / 67:5 / 507

significant difference was observed in HomEM andHetEM for H. pylori eradication in each group. Withoutstratification of HomEM and HetEM, the cure rate in allEMs ranged from 58 to 85%. Despite the higher cure ratein PMs, due to the limited number no statistically signifi-cant difference was observed between CYP2C19 PMs andEMs in each treatment group.

The incidence of adverse effects was 12.5, 12.5 and 25%in groups A, B and C, respectively (Table 7). Althoughadverse events in groups A and B were less frequent, thedifference was not significant. The symptoms were mildand did not result in discontinuation of treatment. Theyincluded a bad taste, loose stools, dizziness, abdominal

distress, and nausea. Drug compliance was 100% in groupsA and B and 95% in group C.

Discussion

CYP2C19 is one of the major enzymes in PPI metabolism.The PK–PD properties of PPIs such as omeprazole, lanso-prazole or pantoprazole are related to the CYP2C19genotype [9]. It is now known that the efficacy ofomeprazole-based H. pylori therapy is dependent on theCYP2C19 genotype. Omeprazole-based therapies withduration >7 days give significantly higher eradication ratesin CYP2C19 PMs than in HomEM [26]. Other studies alsofound a median intragastric pH < 4 in CYP2C19 HomEMtreated with multiple doses of omeprazole for >7 days [9,27]. Rabeprazole is considered to be more active against H.pylori than most PPIs [11–13]. The ability of rabeprazole tomaintain the intragastric pH above 4 in CYP2C19 HomEM isbetter than that of omeprazole [28]. Although rabeprazolemetabolism has been considered to be less affected by theCYP2C19 genotype, CYP2C19 PMs have a significantlyhigher plasma rabeprazole concentration and strongerinhibitory activity on acid secretion [16, 28–31]. Further-more, the concentration of rabeprazole thioether, themajor metabolite of rabeprazole with anti-H. pylori activity,is higher in CYP2C19 PM [14, 32].

In the present study, the population PK analysis showedthat CYP2C19 PMs had a significant lower clearance thanEMs (HomEM and HetEM), resulting in higher plasmarabeprazole levels in CYP2C19 PMs. However, there was nodifferent in PK properties of rabeprazole between HomEMand HetEM. Since the pharmacological activity of PPIs isknown to be dose-dependent [14], the higher plasma con-centration might result in a better response. To confirmthis, further PD analysis was performed using gastrin as asurrogate marker of the intragastric pH [33]. The resultsshowed a correlation between plasma levels of rabepra-zole and gastrin based on a direct link model.A greater andmore rapid gastrin response was observed in CYP2C19PMs on days 4 and 7 of rabeprazole treatment, reflectingstronger acid inhibition. In terms of clinical outcome,

Time after dosing (hr)0 2 4 6 8 10 12

Gas

trin

(pg

/ml)

20

40

60

80

100

120

140

160

180

Figure 1Changes in the plasma gastrin concentration in CYP2C19 poor metabo-lizers and all extensive metabolizers on different days of rabeprazoletreatment. The plots were generated from the pharmacokinetic–pharmacodynamic parameters predicted by NONMEM. Day-1 EM ( );

Day-1 PM ( ); Day-4 EM ( ); Day-4 PM ( ); Day-7 EM ( ); Day-7

PM ( )

Table 6Effects of CYP2C19 genotype and clarithromycin resistance on theeradication rate

GroupH. pylorieradication*

EM† PM p-value (HomEM,HetEM, PM)HomEM HetEM All EM

A S 4 (0) 6 (1) 10 (1) 2 (0) 0.99

F 1 (1) 2 (1) 3 (2) 1 (1)B S 4 (0) 3 (0) 7 (0) 4 (0) 0.17

F 1 (0) 4 (0) 5 (0) 0 (0)

C S 5 (0) 6 (0) 11 (0) 2 (0) 0.60

F 2 (1) 0 (0) 2 (1) 0 (0)

*S, Success; F, Failure. †The values in parentheses indicate the number of subjectsinfected by clarithromycin-resistant H. pylori. HomEM, homozygous extensivemetabolizers; HetEM, heterozygous extensive metabolizers; EM, extensivemetabolizers; PM, poor metabolizers.

Table 7Adverse effects in each treatment group

Group A (n = 16) B (n = 16) C (n = 16)

No. of adverse events 2 2 8Bad taste 2 1 4

Loose stools/diarrhoea 0 1 2Dizziness 0 0 1

Abdominal distress 0 0 1Nausea 0 0 1

Cases with adverse effects (%) 2 (12.5) 2 (12.5) 4 (25)

J-C. Yang et al.

508 / 67:5 / Br J Clin Pharmacol

although the sample size might limit the power for statis-tical analysis and clarithromycin resistance had a greateffect on H. pylori eradication, it was noted that H. pyloriwas successfully eradicated in all CYP2C19 PMs infected byclarithromycin-sensitive H. pylori regardless of the regimenthey received. CYP2C19 PMs tended to have better treat-ment outcomes under both standard (i.e. 7 days) andshort-term H. pylori therapies.

Short-term triple therapy is not regularly used forH. pylori treatment because of the inconsistency in thereported eradiation rates; however, this may be partly dueto the failure to report the CYP2C19 genotypes of the sub-jects [5–7, 34–36]. The successful H. pylori eradication inCYP2C19 PMs seen in the present study suggests the pos-sible use of short-term triple therapy in such patients.In addition, amoxicillin and clarithromycin used in tripletherapy are unstable at a pH < 4 [37]. The faster and bettercontrol of the intragastric pH in CYP2C19 PMs suggeststhat short-term rabeprazole-based triple therapy may beuseful in such patients. Our PK–PD analysis results alsosuggest a higher gastrin response in both CYP2C19 PMsand EMs after multiple doses of rabeprazole. This is inaccordance with the potent and long-acting inhibition ofgastric acid secretion by rabeprazole [38]. When the nextdose is given, acid secretion is still inhibited by the previ-ous dose and a relatively small proportion of the acidsecretion inhibition is contributed by the next dose. Thisphenomenon is reflected by the increased EC50 anddecreased Emax seen after multiple doses. AlthoughCYP2C19 PMs tended to have a better response than EMs,the sufficiently high intragastric pH achieved in bothgroups after multiple doses of rabeprazole may partiallyminimize the difference in H. pylori eradication rate, asobserved with therapies longer than 7 days [26].

Taken together, the PK–PD study showed a betterresponse in CYP2C19 PMs after multiple dosing. Also, atendency of better clinical outcome was observed inCYP2C19 PMs along with a decrease in the number ofadverse events with short-term therapy.Thus, the CYP2C19genotype plays a role in H. pylori eradication therapy, andshort-term rabeprazole-based triple therapy may be appli-cable in CYP2C19 PMs for H. pylori eradication. The possi-bility of the use of short-term triple therapy in CYP2C19PMs may provide further advantages, such as increasedcompliance, reduced cost and less drug resistance.

Competing interests

None to declare.Supported by a grant from the National Taiwan University

Hospital (NTUH. 93S060). The authors thank Mr Hong-Long Wang for his critical assistance with the statisticalanalysis.

REFERENCES

1 Moss SF, Sood S. Helicobacter pylori. Curr Opin Infect Dis2003; 16: 445–51.

2 Howden CW, Hunt RH. Guidelines for the management ofHelicobacter pylori infection. Am J Gastroenterol 1998; 93:2330–8.

3 Chey WD, Wong BC. Practice Parameters Committee of theAmerican College of Gastroenterology. American Collegeof Gastroenterology guideline on the management ofHelicobacter pylori infection. Am J Gastroenterol 2007; 102:1808–25.

4 Calvet X, Gene E, Lopez T, Gisbert JP. What is the optimallength of proton pump inhibitor-based triple therapies forH. pylori? A cost-effectiveness analysis. Aliment PharmacolTher 2001; 15: 1067–76.

5 Gisbert JP, Khorrami S, Calvet X, Pajares JM. Systematicreview: rabeprazole-based therapies in Helicobacter pylorieradication. Aliment Pharmacol Ther 2003; 17: 751–64.

6 Vakil N, Schwartz HJ, Lanza FL, Nardi L, Hahne W, Barth J. Aprospective, controlled, randomized trial of 3-, 7-, and 10-dayrabeprazole-based triple therapy for H. pylori eradication inthe USA. Gastroenterology 2002; 122 (Suppl. 4): A65.

7 Luth S, Teyssen S, Kolbel CB, Singer MV. 4-day triple therapywith rabeprazole, amoxicillin and clarithromycin in theeradication of Helicobacter pylori in patients with pepticulcer disease – a pilot study. Z Gastroenterol 2001; 39:279–85.

8 Sachs G, Shin JM, Vagin O, Lambrecht N, Yakubov I,Munson K. The gastric H,K-ATPase as a drug target: past,present and future. J Clin Gastroenterol 2007; 41: S226–42.

9 Klotz U, Schwab M, Treiber G. CYP2C19 polymorphism andproton pump inhibitors. Basic Clin Pharmacol Toxicol 2004;95: 2–8.

10 Goldstein JA, Ishizaki T, Chiba K, de Morais SM, Bell D,Krahn PM, Evans DA. Frequencies of the defective CYP2C19alleles responsible for the mephenytoin poor metabolizerphenotype in various Oriental, Caucasian, Saudi Arabian andAmerican black populations. Pharmacogenetics 1997; 7:59–64.

11 Besancon M, Simon A, Sachs G, Shin JM. Sites of reaction ofthe gastric H,K-ATPase with extracytoplasmic thio reagents.J Biol Chem 1997; 272: 22438–46.

12 Tsutsui N, Taneike I, Ohara T, Goshi S, Kojio S, Iwakura N,Matsumaru H, Wakisaka-Saito N, Zhang HM, Yamamoto T.A novel action of the proton pump inhibitor rabeprazoleand its thioether derivative against the mobility ofHelicobacter pylori. Antimicrob Agents Chemother 2000; 44:3069–73.

13 Tsuchiya M, Imamura L, Park JB, Kobashi K. Helicobacterpylori urease inhibition by rabeprazole, a proton pumpinhibitor. Biol Pharm Bull 1995; 18: 1053–6.

14 Williams MP, Pounder RE. Review article: the pharmacologyof rabeprazole. Aliment Pharmacol Ther 1999; 13 (Suppl. 3):3–10.

CYP2C19 genotypes in short-term triple therapy

Br J Clin Pharmacol / 67:5 / 509

15 Inaba T, Mizuno M, Kawai K, Yokota K, Oguma K, Miyoshi M,Take S, Okada H, Tsuji T. Randomized open trial forcomparison of proton pump inhibitors in triple therapy forHelicobacter pylori infection in relation to CYP2C19genotype. J Gastroenterol Hepatol 2002; 17: 748–53.

16 Horai Y, Kimura M, Furuie H, Matsuquma K, Irie S, Koga Y,Nagahama T, Murakami M, Matsui T, Yao T, Urae A, Ishizaki T.Pharmacodynamic effects and kinetic disposition ofrabeprazole in relation to CYP2C19 genotypes. AlimentPharmacol Ther 2001; 15: 793–803.

17 Lin CJ, Yang JC, Uang YS, Chern HD, Wang TH. Time-dependent amplified pharmacokinetic and pharmacody-namic responses of rabeprazole in cytochrome P450 2C19poor metabolizers. Pharmacotherapy 2003; 23: 711–9.

18 Sugimoto M, Furuta T, Shirai N, Kodaira C, Nishino M,Yamade M, Ikuma M, Watanabe H, Ohashi K, Hishida A,Ishizaki T. Treatment strategy to eradicate Helicobacter pyloriinfection: impact of pharmacogenomics-based acidinhibition regimen and alternative antibiotics. Expert OpinPharmacother 2007; 8: 2701–17.

19 Yang JC, Yang KC, Hsu CT, Wang CS, Kuo CF, Wang TH. Amulticenter study on eradication of Helicobacter pyloriinfection in patients with duodenal ulcer bylansoprazole-antibiotics combined therapy. J MicrobiolImmunol Infect 1999; 32: 1–8.

20 Sambrook J, Russell DW. Molecular Cloning: a LaboratoryManual, 3rd edn. Cold Spring Harbor, NY: Cold Spring HarborLaboratory, 2001; 6.8–6.10.

21 Morais SMF, Wilkinson GR, Blaisdell J, Meyer UA, Nakamura K,Goldstein JA. Identification of a new genetic defectresponsible for the polymorphism of (S)-mephenytoinmetabolism in Japanese. Mol Pharmacol 1994; 46: 594–8.

22 Morais SMF, Wilkinson GR, Blaisdell J, Nakamura K, Meyer UA,Goldstein JA. The major genetic defect responsible for thepolymorphism of S-mephenytoin metabolism in humans.J Biol Chem 1994; 269: 15419–22.

23 Nakai H, Shimamura Y, Kanazawa T, Yasuda S, Kayano M.Determination of a new H+-K+ ATPase inhibitor (E3810) andits four metabolites in human plasma by high-performanceliquid chromatography. J Chromatogr B 1994; 660: 211–20.

24 Sheiner LB, Stanski DR, Vozeh S, Miller RD, Ham J.Simultaneous modeling of pharmacokinetics andpharmacodynamics: application to d-tubocurarine. ClinPharmacol Ther 1979; 25: 358–71.

25 Mosteller RD. Simplified calculation of body surface area.N Engl J Med 1987; 317: 1098.

26 Padol S, Yuan Y, Thabane M, Padol IT, Hunt RH. The effect ofCYP2C19 polymorphisms on H. pylori eradication rate in dualand triple first-line PPI therapies: a meta-analysis. Am JGastroenterol 2006; 101: 1467–75.

27 Sagar M, Tybring G, Dahl ML, Bertilsson L, Seensalu R. Effectsof omeprazole on intragastric pH and plasma gastrin aredependent on the CYP2C19 polymorphism.Gastroenterology 2000; 119: 670–6.

28 Shirai N, Furuta T, Moriyama Y, Okochi H, Kobayashi K,Takashima M, Xiao F, Kosuge K, Nakagawa K, Hanai H,

Chiba K, Ohashi K, Ishizaki T. Effects of CYP2C19 genotypicdifferences in the metabolism of omeprazole andrabeprazole on intragastric pH. Aliment Pharmacol Ther2001; 15: 1929–37.

29 Ieiri I, Kishimoto Y, Okochi H, Momiyama K, Morita T,Kitano M, Morisawa T, Fukushima Y, Nakagawa K,Hasegawa J, Otsubo K, Ishizaki T. Comparison of the kineticdisposition of and serum gastrin change by lansoprazoleversus rabeprazole during an 8-day dosing scheme inrelation to CYP2C19 polymorphism. Eur J Clin Pharmacol2001; 57: 485–92.

30 Sugimoto M, Furuta T, Shirai N, Kajimura M, Hishida A,Sakurai M, Ohashi K, Ishizaki T. Different dosage regimens ofrabeprazole for nocturnal gastric acid inhibition in relationto cytochrome P450 2C19 genotype status. Clin PharmacolTher 2004; 76: 290–301.

31 Sugimoto M, Furuta T, Shirai N, Nakamura A, Kajimura M,Hishida A, Ohashi K, Ishizaki T. Comparison of an increaseddosage regimen of rabeprazole versus a concomitantdosage regimen of famotidine with rabeprazole fornocturnal gastric acid inhibition in relation to cytochromeP450 2C19 genotypes. Clin Pharmacol Ther 2005; 77: 302–11.

32 Yasuda S, Horai Y, Tomono Y, Nakai H, Yamato C, Manabe K,Kobayashi K, Chiba K, Ishizaki T. Comparison of the kineticdisposition and metabolism of E3810, a new proton pumpinhibitor, and omeprazole in relation to S-mephenytoin 4′-hydroxylation status. Clin Pharmacol Ther 1995; 58: 143–54.

33 Williams MP, Blanshard C, Millson C, Sercombe J, Pounder RE.A placebo-controlled study to assess the effects of 7-daydosing with 10, 20 and 40 mg rabeprazole on 24-hintragastric acidity and plasma gastrin in healthy malesubjects. Aliment Pharmacol Ther 2000; 14: 691–9.

34 Gambaro C, Bilardi C, Dulbecco P, Iiritano E, Zentilin P,Mansi C, Usai P, Vigneri S, Savarino V. ComparableHelicobacter pylori eradication rates obtained with 4- and7-day rabeprazole-based triple therapy: a preliminary study.Dig Liver Dis 2003; 35: 763–7.

35 Isomoto H, Furusu H, Morikawa T, Mizuta Y, Nishiyama T,Omagari K, Murase K, Inoue K, Murata I, Kohno S. 5-day vs.7-day triple therapy with rabeprazole, clarithromycin andamoxicillin for Helicobacter pylori eradication. AlimentPharmacol Ther 2000; 14: 1619–23.

36 Wong BC, Wong WM, Yee YK, Hung WK, Yip AWC, Szeto ML,Li KF, Lau P, Fung FMY, Tong TSM, Lai KC, Hu WHC, Yuen MF,Hui CK, Lam SK. Rabeprazole-based 3-day and 7-day tripletherapy vs. omeprazole-based 7-day triple therapy for thetreatment of Helicobacter pylori infection. Aliment PharmacolTher 2001; 15: 1959–65.

37 Erah PO, Goddard AF, Barrett DA, Shaw PN, Spiller RC. Thestability of amoxycillin, clarithromycin and metronidazole ingastric juice: relevance to the treatment of Helicobacterpylori infection. J Antimicrob Chemother 1997; 39: 5–12.

38 Ohning GV, Barbuti RC, Kovacs TO, Sytnik B, Humphries TJ,Walsh JH. Rabeprazole produces rapid, potent, andlong-acting inhibition of gastric acid secretion in subjectswith Helicobacter pylori infection. Aliment Pharmacol Ther2000; 14: 701–8.

J-C. Yang et al.

510 / 67:5 / Br J Clin Pharmacol