Effect of dosing schemes of amoxicillin on eradication rates of Helicobacter pylori with amoxicillin-based triple therapy.

Objectives: In standard regimens for Helicobacter pylori infection, amoxicillin is dosed twice daily, although the bactericidal effect of amoxicillin depends on the %time-above-MIC. We aimed to examine whether dosing schemes of amoxicillin influenced eradication rates of amoxicillin-based regimens.

Methods: One hundred eighty-seven patients infected with clarithromycin-sensitive strains of H. pylori were treated with PPI, clarithromycin 200 mg bid and amoxicillin 750 mg bid, 500 mg tid or 500 mg qid for 1 week and 125 infected with clarithromycin-resistant strains were treated with PPI, metronidazole 250 mg bid and amoxicillin 750 mg bid, 500 mg tid or 500 mg qid for 1 week.

Results: Eradication rates (ITT) of the triple PPI/amoxicillin/clarithromycin therapy with bid, tid and qid dosings of amoxicillin were 77.8% (49/63), 93.5% (58/62), and 91.9% (57/62), respectively. Those of the triple PPI/amoxicillin/metronidazole therapy were 80.5% (33/41), 90.5% (38/42), and 95.2% (40/42), respectively. Eradication rates in regimens with tid and qid dosing of amoxicillin were higher than those of regimens with the bid dosing of amoxicillin.

Conclusions: The dosing scheme of amoxicillin significantly influenced eradication rates of triple therapies. Although amoxicillin is empirically dosed twice daily, amoxicillin should be dosed at least three times daily in amoxicillin-based triple therapies.