The optimal pharmacological regimen for eradication of Helicobacter pylori (H. pylori) has been investigated for many years. This study aimed to evaluate the efficacy and tolerability of bismuth-based quadruple therapy (B-QT) and a modified sequential therapy (ST) regimens in eradication of H. pylori.

A randomized, double-blind trial conducted on 344 patients. Patients with H. pylori infection and without a history of previous treatment were randomized to receive 14-day B-QT (bismuth subcitrate 240 mg, pantoprazole 40 mg, amoxicillin 1000 mg, and clarithromycin 500 mg twice daily) or 14-day ST (bismuth subcitrate 240 mg, pantoprazole 40 mg, amoxicillin 1000 mg, and metronidazole 500 mg twice daily for seven days followed by bismuth subcitrate 240 mg, pantoprazole 40 mg, amoxicillin 1000 mg, and furazolidone 100 mg twice daily for additional seven days). Drug adverse effects were assessed during the study. H. pylori eradication was determined eight weeks after the end of treatment using 14C-urea breath test.

Based on per-protocol and intention-to-treat, the eradication rate was significantly higher (p<0.05) in the B-QT regimen 91.9% (95% CI; 88.1-94.0) and 90.2% (95% CI; 86.3-92.9), respectively compared to the ST regimen 80.8 % (95% CI; 76.6-84.9) and 78.1% (95% CI; 73.7-82.4), respectively. The severity of vomiting and loss of appetite were significantly higher in ST regimen (p<0.05).

The B-QT regimen was more effective and safe than the ST regimen. Conclusively, it is suggested to assess the efficacy and safety of this regimen in longer studies, larger population, and in other communities.