CYP2C19 genotype status and intragastric pH during dosing with lansoprazole or rabeprazole

Background: CYP2C19 has an important role in the catabolism of several prot on pump inhibitors. However, the relative contribution of CYP2C19-mediated metabolism varies among the different proton pump inhibitors. Aim: To determine the effect of CYP2C19 genotype status on intragastric pH during dosing with lansoprazole or rabeprazole. Subjects and methods: The subjects were 20 male volunteers without Helicoba cter pylori infection. Their CYP2C19 genotype status was determined by a po lymerase chain reaction-restriction fragment length polymorphism method. Tw enty-four-hour monitoring of intragastric acidity was performed three times : once without medication, once on the last day of a 7-day course of rabepr azole, and once on the last day of a 7-day course of lansoprazole. Results: Subjects were divided into three groups on the basis of their CYP2 C19 genotype status: homozygous extensive metabolizers (homo-EMs, n=7), het erozygous extensive metabolizers (hetero-EMs, n=9), and poor metabolizers ( PMs, n=4). The median pH during rabeprazole administration was not influenc ed by CYP2C19 genotype. On the other hand, the median pH in PMs during lans oprazole dosing was higher than in homo-EMs and hetero-EMs. The percentage of time with pH < 4.0 had a similar tendency to that of median pH. Conclusion: CYP2C19 genotype status influences gastric acid suppression by lansoprazole, but not by rabeprazole.