Esomeprazole is one of the most commonly used drugs to treat
gastroesophageal reflux disease and
peptic ulcers, but the quantitative relationships among the pharmacokinetics (PK), pharmacodynamics (PD), and pharmacogenomics (PG) of the drug are not fully understood in special patient populations. A clinical PK/PD/PG study of intravenous (IV)
esomeprazole in 5 dosing regimens was conducted in 20 healthy Chinese volunteers, who were categorized into Helicobacter pylori (HP)-negative and HP-positive subgroups. Plasma
esomeprazole concentration and intragastric H(+) concentration were monitored for 24 hours postdosing. Population PK (PopPK) models were tested based on elimination characteristics and other data. For a single-dose IV
esomeprazole regimen, a 2-compartment model with nonlinear elimination characteristics fitted the PK data well. The elimination of
esomeprazole was found to be significantly linked to
CYP2C19 genotype by 11% to 29%. A mechanism-based PD model was first tested to mimic the irreversible inhibition of H(+) /K(+) -
ATPase by
esomeprazole using a cell-killing mechanism and models of gastric H(+) secretion that included the effects of an asymmetric circadian rhythm and food effects. Results from this PD model showed that the turnover rate of H(+) /K(+) -
ATPase was significantly different between HP-negative and HP-positive subgroups. In conclusion, the PopPK model quantitatively identified the effects of the
CYP2C19 genotype on
esomeprazole elimination in healthy subjects for the first time. In addition, the effects of HP status on drug effect, H(+) /K(+) -
ATPase turnover, and circadian rhythm amplitude were preliminarily explored using a mechanism-based PD model.