The impact of primary antibiotic resistance on the efficacy of ranitidine bismuth citrate- vs. omeprazole-based one-week triple therapies in H. pylori eradication - a randomised controlled trial

Aims: To compare ranitidine bismuth citrate with omeprazole as to their efficacy to eradicate H. pylori in two different treatment schedules both consisting of a combination of either of above with two antibiotics for 1 week, and to relate these treatment results to primary antibiotic resistance. Methods: 256 H. pylori positive patients with non-ulcer dyspepsia were randomised to one of the following four treatment groups: omeprazole 20 mg + clarithromycin 500 mg + amoxycillin 1000 mg (OCA); ranitidine bismuth citrate 400 mg + clarithromycin 500 mg + amoxycillin 1000 mg (RBCCA); omeprazole 20 mg + clarithromycin 500 mg + metronidazole 500 mg (OCM); ranitidine bismuth citrate 400 mg + clarithromycin 500 mg + metronidazole 500 mg (RBCCM). All drugs were given twice daily for one week. The patients were assessed for prevalence of H. pylori by CLO test, histology and culture on gastric biopsy samples obtained during upper gastrointestinal endoscopy before randomisation and 4-6 weeks after completion of therapy. Bacterial sensitivity to clarithromycin, metronidazole and amoxycillin was determined by E-test. Results: On per-protocol analysis, overall eradication rates were 96% for RBCCA vs. 85% for OCA (p = 0.03), and 95% for RBCCM vs. 79% for OCM (p = 0.01). Amongst the 196 patients (77% of the entire study group) in whom antibiotic sensitivity testing was technically feasible, primary resistance was found in 8% for clarithromycin, in 33% for metronidazole, and in 0% for amoxycilline. Eradication of clarithromycin sensitive/resistant strains was 89%/40% for OCA (p = 0.0042) and 98%/80% for RBCCA (p = 0.0428). When strains were sensitive to both antibiotics, cure rates with OCM/RBCCM were 87%/96% respectively (p = 0.39), for strains resistant to clarithromycin only, eradication was achieved in 82% with OCM vs. 94% with RBCCM (p=0.2), and in the case of metronidazole resistance in 85% with OCM vs. 94% with RBCCM (p=0.09). Conclusions: Ranitidine bismuth citrate in combination with clarithromycin and either metronidazole or amoxycilline produced higher eradication rates than omeprazole co-administered with the same antibiotics. This appeared especially prominent in the subgroups with clarithromycin resistance without, however, reaching statistical significance. Efficacy of neither eradication regimen was influenced by metronidazole sensitivity to a significant degree.