Background: Helicobacter pylori eradication usually fails when clarithromycin is used against resistant strains.
Objective: The objective of this study was to test whether the apparent synergy found in vitro between ranitidine bismuth citrate (RBC) and clarithromycin also exists in vivo against resistant strains.
Methods: H. pylori was cultured and clarithromycin susceptibility was determined before and after treatment, from duodenal ulcer patients receiving RBC and clarithromycin or omeprazole and clarithromycin for 2 weeks in a multicenter randomized clinical trial.
Results: The overall eradication rate was 88.7% in the RBC group (71 patients) and 52.7% in the omeprazole group (74 patients). The demographic characteristics of the two groups were not different. Clarithromycin-resistant strains were isolated in 22 cases (15.1%). A difference between the eradication rates of susceptible and resistant strains was found in the omeprazole group but not in the RBC group. After treatment, resistance to clarithromycin developed in three of the seven strains (42.3%) cultured from the patients of the RBC group, compared with 11 of the 26 strains (42%) of the omeprazole group. That is, clarithromycin-resistant strains were found in 6% and 27% in the RBC group and the omeprazole group, respectively, on considering the global results.
Conclusion: A synergy between RBC and clarithromycin may exist in vivo and, while clarithromycin resistance is increasing, it is an argument for using RBC in triple therapies.