Through our analysis, we demonstrated that some factors that can affect the outcome of H. pylori eradication treatment by tailored therapy based on PPI are esomeprazole in pediatric patients with gastritis and peptic ulcer including age, gastroduodenal disease diagnosis, CYP2C19 phenotypes, and MDR1 C3435T genotype. Here, CYP2C19 is linked to peptic ulcer disease.