Diminishing Efficacy of Second-Line Levofloxacin-Based Quadruple Therapy in Helicobacter pylori Eradication: A Prospective Real-World Study in Vietnam Amid Rising Antibiotic Resistance.

Background/Objectives:Helicobacter pylori (H. pylori) infection remains highly prevalent in Vietnam, associated with chronic gastritis, peptic ulcers, and gastric cancer. This study aimed to evaluate the real-world eradication rate of levofloxacin-based bismuth quadruple therapy (PALB) as second-line treatment, assess adherence, and identify associated factors with treatment success. Methods: We conducted a prospective cohort study including 225 patients with confirmed failure of classical bismuth-based quadruple therapy. All received a 14-day PALB regimen. H. pylori eradication was assessed using 13C-urea breath test and/or rapid urease test 4-12 weeks after treatment. Results: Eradication rates were 78.2% (mITT) and 78.6% (PP), with 95% CIs overlapping the 80% benchmark. Adherence was high (91.6%) and significantly associated with success (OR = 2.93; 95% CI: 1.11-7.74; p = 0.039). No other factors were significantly associated. Conclusions: While PALB remains a valid second-line therapy, its efficacy may be declining, though not statistically inferior to 80%. Improving adherence and strengthening stewardship are essential.