Study of the effect of CYP2C19 polymorphisms on omeprazole pharmacokinetics by utilizing validated LC–MS/MS and Real Time-PCR methods

A fully automated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the determination of omeprazole in human plasma. Utilization of 96-well plates and robotic liquid handling workstations, rendered the whole procedure very fast, compared to the manual respective procedure of Liquid-Liquid Extraction (LLE). Sample analysis was performed by reversed phase LC-MS/MS, with positive electrospray ionization, using multiple reaction monitoring (MRM). The method required low plasma volumes and analysis of samples was completed in short run times. It was fully validated and applied to a pharmacokinetic study after per os administration of 20mg tablet formulations of omeprazole. The obtained concentrations were used for the calculation of the basic omeprazole pharmacokinetic parameters. Some variations observed in pharmacokinetic parameters among subjects were attributed to differences of CYP2C19 genotype. Therefore, a novel molecular method was developed in which DNA analysis was conducted by using Real Time-Polymerase Chain Reaction (Real Time-PCR). As source of biological material, Dried Blood Spots (DBS) were utilized, offering an alternative and advantageous strategy for such kind of studies.