Purpose. A combination of proton pump inhibitors and antimicrobials has bee
n applied as an anti-Helicobncrer pylori (N. pylori) therapy. Omeprazole, o
ne of the proton pump inhibitors, is metabolized by CYP2C19, which exhibits
genetic polymorphism. It was reported previously that the overall anti-H.
pylori efficacy can be related to the CYP2C19 genotype. The main aim of the
present study was to obtain a rational explanation for the relationship be
tween the overall anti-H. pylori efficacy and the CYP2C19 genotype.
Methods. Six healthy volunteers were classified as extensive metabolizers a
nd poor metabolizers, according to their CYP2C19 genotypes. Plasma concentr
ations and intragastric pH were monitored prior to and until 24 h after the
administration of 20 mg omeprazole. The stability of amoxicillin, clarithr
omycin, and metronidazole was examined using buffer solutions with monitore
d intragastric pH, and their remaining percentage in the intragastric space
was simulated.
Results. The poor metabolizers, classified by the CYP2C19 genotypes, showed
the higher effectiveness in anti-H. pylori therapy, via the higher plasma
concentration of omeprazole and the higher intragastric pH, and possibly th
e higher stability of antimicrobials in the higher intragastric pH.
Conclusions. CYP2C19 genotyping is a very useful method to determine the ef
fective and safe dosage regimen including the selection of the dual and tri
ple therapy in anti-H. pylori therapy.