effects of clarithromycin-containing quadruple therapy on helicobacter pylori eradication after nitroimidazole- containing quadruple therapy failure

background: several large clinical trials and meta-analyses have shown about 20% failure to eradicate helicobacter pylori ( h. pylori ), necessitating investigations for second-line treatments. the aim of this study was to evaluate the effects of clarithromycin-containing quadruple regimen after nitroimidazole-containing quadruple therapy failure. methods: thirty two patients who had failed 10-day h. pylori treatment with omeprazole, amoxicillin, bismuth subcitrate, and metronidazole (oabm)  regimen and 31 patients who had failed 10-day treatment with omeprazole, amoxicillin, bismuth subcitrate, and furazolidone (oamf) regimen entered the study. they all received omeprazole (20 mg), amoxicillin (1 gr), bismuth subcitrate (240 mg) and clarithromycin (500 mg) twice a day for 10 days. eight weeks after treatment, h. pylori eradication was assessed by ¹⁴c-urea breath test. results: totally 61 patients completed the study. according to intention to treat (itt) analysis, eradication rates by second-line oabc regimen were 84.37% (95% ci= 71.7–96.9%) in oabm group and 77.41% (95% ci= 62.71–92.11%) in oabf group (p=0.756). per-protocol (pp) eradication rates were 87.09% (95% ci= 75.2–98.8%) and 82.75% (95% ci= 79.4–96%), respectively (p=0.638). also the cumulative eradication rates by oabc regimen were 80.9% (95% ci= 71.2–90.6%) and 85% (95% ci= 75.9–94%) according to itt and pp analyses, respectively. severe side effects were reported in 3.1% of the patients. conclusion: regarding ideal eradication rate (>80%) and very low adverse effects, it seems that clarithromycin-containing quadruple therapy can be an encouraging regimen after nitroimidazole-containing regimen failure.