Background: The success of eradication therapy for Helicobacter pylori might be affected by the age of patients. Aim: To investigate whether disposition of drugs commonly used for H. pylori eradication is age-dependent. Methods: Trough steady state serum levels of lansoprazole or ranitidine, amoxycillin, clarithromycin and metronidazole were monitored in 232 patients during the last dosing interval of a 5-day quadruple H. pylori eradication regimen. Detailed pharmacokinetic analysis was performed in 28 patients. Results: Linear correlations between age and trough serum levels were observed with lansoprazole (r=0.25; P=0.002), ranitidine (r=0.38; P=0.001) and clarithromycin (r=0.36; P