helicobacter pylori ( h. pylori ) is a gram - negative bacillus that inhabits the gastric mucosa and mucus . h. pylori infection is now known to be a risk factor of a wide range of diseases , such as atrophic gastritis , gastroduodenal ulcer , mucosa - associated lymphoid tissue ( malt ) lymphoma , gastric cancer , and idiopathic thrombocytopenic purpura ( itp ) [ 14 ] . furthermore , the recurrence of early gastric cancer after its endoscopic resection was reported to be reduced to almost one - third if h. pylori was successfully eradicated . in japan 150,000 deaths from gastric cancer will be prevented over 5 years if all h. pylori is eliminated . the first - line eradication therapy of h. pylori in japan is triple therapy , consisting of a proton pump inhibitor ( ppi ) , amoxicillin ( ampc ) , and clarithromycin ( cam ) . this regimen has been covered by the national health insurance system since december 2000 . however , due to the increase of cam - resistant h. pylori strains , the eradication rate of first - line therapy is reported to be as low as 75% . second - line eradication therapy , consisting of ppi , ampc , and metronidazole ( mnz ) , has been approved in japan for those who fail the first - line therapy . the eradication rate of the second - line therapy has been reported to be around 90% [ 8 , 9 ] . these results indicate that about 3% of h. pylori positive patients fail in both first- and second - line therapy . from 2013 , the eradication treatment for h. pylori infection with chronic gastritis as the number of the patients who are eligible for the eradication of h. pylori is estimated to be increasing , it is becoming more important to establish standard third - line eradication therapy . the guidelines of the japanese society of helicobacter research suggest ppi + ampc + levofloxacin ( lvfx ) or high - dose ppi + ampc as the third - line eradication regimen in 2009 . in the former regimen , the rate of eradication was reported to be 43.170.0% if it was used as third - line therapy [ 10 , 11 ] . in the latter regimen , the rate of eradication was reported to be 54.3% if it was used as third - line therapy . until now , which regimen is more effective for third - line eradication therapy has not been clarified sufficiently . the aim of this study was to investigate and compare the eradication rate of third - line triple therapy with rabeprazole ( rpz ) + ampc + lvfx to high - dose rpz + ampc which were suggested in the guidelines of the japanese society of helicobacter research in 2009 . this was a prospective , randomized , controlled study conducted in chiba university hospital . from june 2011 to june 2013 , patients who failed japanese first - line ( ppi + ampc + cam ) and second - line ( ppi + ampc + mnz ) eradication therapy were randomly assigned to one of the following third - line eradication groups at a 1  :  1 ratio using random number tables : ( 1 ) ral group : rpz 10  mg ( b.i.d . ) , ampc 750  mg ( b.i.d . ) , and lvfx 500  mg ( o.d . ) for 10 days ; ( 2 ) ra group : rpz 10  mg ( q.i.d . ) and ampc 500  mg ( q.i.d . ) for 14 days . patients ( 1 ) who had a past history of allergy to the study drugs , ( 2 ) who had severe liver dysfunction , ( 3 ) who were undergoing treatment of malignant disease , ( 4 ) who were pregnant or lactating , or ( 5 ) who were ineligible to participate in this study according to the decision of a physician were excluded from this study . the secondary endpoints were the safety of treatment and the efficacy of fourth - line treatment . before being randomized , all patients underwent upper endoscopy and we performed h. pylori sensitivity testing for the antibiotics ( ampc , cam , mnz , and lvfx ) . six to twelve weeks after the end of the third - line eradication therapy , a c - urea breath test ( ubt ) was performed . patients who failed to respond to third - line eradication therapy received salvage therapy as the fourth - line one . in this regimen , patients who were treated with ral received ra ( salvage ra group ) and those treated with ra received ral ( savage ral group ) . six to twelve weeks after the end of the salvage therapy , h. pylori eradication was assessed again with ubt . during the study , blood samples were taken from the patients to analyze the cytochrome p450 2c19 ( cyp2c19 ) polymorphism . the study protocol was approved by chiba university institutional review board and registered ( clinical registration number , umin000005373 ) . all patients underwent ubt before third - line eradication to check for the presence of h. pylori . at 612 weeks after the third - line therapy and salvage therapy , the patients whose ubt results were negative were considered to have eradicated the infection . before ubt , ppi , which may influence the test results , was discontinued for at least 2 weeks . h. pylori strains were isolated from tissue samples from the gastric corpus and antibiotic sensitivity testing was performed using the e - test . the breakpoints were 1.0  g / ml for abpc , cam , and lvfx and 8.0  g / ml for mnz . an h. pylori strain was judged resistant to the antibiotics when its minimum inhibitory concentrations ( mic ) value was equal to or beyond the breakpoint . genotyping of the two mutated genes was performed using the gene analysis by fluorescence correlation spectroscopy ( gfcs ) method with blood serum samples from the patients . the cyp2c19 gene polymorphisms were classified into three types : cyp2c19 wild type gene ( cyp2c191 ) and two mutated genes ( cyp2c192 and cyp2c193 ) . patients with ( 1/1 ) were categorized as the homogeneous extensive metabolizers ( em ) . patients with ( 1/2 ) or ( 1/3 ) were categorized as the heterogeneous em . and patients with ( 2/3 ) , ( 2/2 ) , or ( 3/3 ) were categorized as the poor metabolizers ( pm ) . adverse events ( ae ) were evaluated by asking the patients about their condition and laboratory evaluation of liver and renal function , which was performed two weeks after the end of the third - line eradication therapy . statistical analysis of the third and overall eradiation rates was performed between two groups using the chi - square test . each parameter of the patient background was analyzed using the chi - square test or unpaired t - test . , chicago , il , usa ) , with p < 0.05 considered statistically significant . fifty - one patients were enrolled in this study and the study flow of the patients is shown in figure 1 . the 51 patients were randomly assigned to the ral group ( n = 24 ) or ra group ( n = 27 ) ( intension to treat ( itt ) analysis subjects set ) . three patients in the ra group were excluded from the per - protocol ( pp ) analysis because two refused treatment and one did not visit the hospital . as a result , twelve patients in the ral group and eleven patients in the ra group underwent salvage therapy . one patient in the ral group and two patients in the ra group did not consent to salvage therapy . one patient in the salvage ral group who refused treatment was excluded from pp analysis . consequently , twelve patients in the ral group and ten patients in the ra group were included in the pp analysis . h. pylori was eradicated from six patients in the ral group ( salvage ra group ) and five patients in the ra group ( salvage ral group ) . the backgrounds of the patients , based on pp analysis , are shown in table 1 . the two groups had similar characteristics with respect to age , sex , body mass index ( bmi ) , reasons for the eradication , and success rate of the drug sensitivity test . the success rate of the drug sensitivity testing was defined as the ratio of number of cases with them to all cases . the number of cyp2c19 em was significantly higher in the ral group than in the ra group ( p < 0.05 ) . the rates of eradication , based on itt analysis , were 45.8% for the ral group and 40.7% for the ra group and there was no significant difference ( p = 0.71 ) . in the pp analysis , the rates of eradication were the same ( 45.8% ) in both groups . table 2 shows a comparison , based on pp analysis , of the patients ' backgrounds , between the success and failure groups in the third - line eradication therapy . there was no difference with respect to sex , bmi , eradication therapy , drug resistance , and cyp2c19 polymorphism . the age ( mean  s.d . ) of the success group was 64.1  10.0 , which was significantly higher than that of the failure group ( 56.2  13.5 , p < 0.05 ) . the success rate of the drug sensitivity test was significantly higher for the failure group than for the success group ( 80.0% versus 36.4% , p < 0.05 ) . the rates of eradication success in salvage eradication therapy were 50.0% in the ral group ( salvage ra group ) and 45.5% in the ra group ( salvage ral group ) , based on itt analysis . the overall eradication rate ( third - line and salvage therapy eradication rate ) was 73.9% in the ral group and 64.0% in the ra group , based on itt analysis ( p = 0.46 ) . in pp analysis , the overall eradication rate was 73.9% in the ral group and 76.2% in the ra group ( p = 0.86 ) , which showed no significant difference ( chi - square test , figure 2 ) . ae of the third - line eradication therapy is shown in table 3 . in both groups , the most frequently observed ae was soft stool / diarrhea ( 20.8% in both groups ) . a rash was observed in one patient ( 4.2% ) in the ral group and one patient in the ra group ( 4.2% ) had nausea . there was no significant difference between the two groups regarding any ae and all ae were reversible . recently , sitafloxacin- ( stfx- ) based third - line eradication therapy has been reported to be effective , with an eradication rate of 7083.6% [ 1113 ] . the reasons for the relatively high eradication rate might be attributable to the following factors . the dna gyrase subunit a ( grya ) mutation is known to be responsible for the resistance of h. pylori to quinolones . it was reported that the mic ( 50 ) ( mic for 50% of the organisms ) of stfx against gyra mutants is 0.12  g / ml , significantly lower than that of lvfx ( 8  g / ml ) . furthermore , the h. pylori resistance rate to stfx was 7.7% , which was lower than that of lvfx . although stfx has some benefits , it is available only in japan and thailand now . taking this current state into consideration , lvfx - based triple therapy and high - dose ppi and ampc dual therapy may be widely available in many countries , as well as in japan . in a previous study , stfx - based third - line therapy was superior to that based on lvfx but the regimen requires patients to take lvfx 300  mg ( b.i.d ) . in our lvfx - based triple therapy , the patients take lvfx 500  mg ( o.d . ) . because lvfx is dependent on concentration , the eradication rate of the ral group was 45.8% on itt analysis , which was almost the same as the ra group ( 40.7% ) . the third - line ral or ra may be inferior to stfx - based therapy . in this study , lvfx and ampc were selected as the antibiotics for the third - line and salvage eradication therapy . currently , lvfx is used for a wide range of infectious diseases and is the most frequently used quinolone for h. pylori eradication . as a result , the resistance rate of h. pylori to lvfx has been reported to be 3957% [ 11 , 15 ] . in this study on the other hand , the resistance rate of h. pylori to ampc has been reported to be low in japan , the united states , europe , and china . consequently the eradication rate of a high - dose ppi + ampc regimen has been reported to be 90.9 to 100% when used as second - line eradication therapy [ 17 , 18 ] . reported that the resistance rate of h. pylori to ampc in patients who failed both first- and second - line ampc - based eradication therapy was 8.2% and the eradication rate of a high - dose ppi + ampc regimen as the third - line therapy was 54.3% . it is possible that a proportion of h. pylori strains acquire resistance to ampc during first- and second - line eradication therapy . in our study , although the rate of resistance of h. pylori to ampc was 0% , 40.4% of the patients had failed the drug sensitivity test and , in some of these cases , ampc - resistant h. pylori strains may have been present . this could be a cause of the low eradication rate ( 40.7% on itt analysis ) . increased ppi dosing was reported to be critical for the success of h. pylori eradication . the percentages of the em and pm genotypes of cyp2c19 are 89% and 11% , respectively . reported that patients with the pm genotype of cyp2c19 achieved a high h. pylori eradication rate compared to those with em . among the many ppis , rabeprazole is mainly reduced to rabeprazole thioether by a nonenzymatic pathway and partially metabolized to demethylated rabeprazole by cyp2c19 . rabeprazole was used in this study and the ratio of em did not differ significantly between the success and failure groups in third - line eradication therapy . secondly , a comparison with stfx - based therapy was not implemented . in the future , a large scale prospective study , including other suggestive regimens , should be carried out to establish standard third - line eradication therapy for h. pylori . thirdly , in spite of randomization , there exists some difference of the clinical background between ral and ra groups . because the success rate of h. pylori eradication with third - line therapy or salvage therapy did not show the difference between ral and ra groups , we speculated that the influence of this uneven distribution might be low . in conclusion , as the third - line triple therapy , the eradication rate with rabeprazole , ampc , and lvfx for 10 days was equal to that with high - dose rabeprazole and ampc for 14 days . these efficacy rates were not high but can be an alternative therapy after second - line failure because these therapies seemed free from severe adverse events .