On-Line Enantioselective Capillary Electrophoretic Method for Screening Cytochrome P450 3A4 Inhibitors

The market share of single-enantiomer drugs is steadily increasing. The pharmacodynamics and pharmacokinetics of individual enantiomers could differ considerably. Thus, their characteristics have to be addressed as early as possible in the development process of new pharmaceuticals. Capillary electrophoresis is a promising technique for enantioselective drug metabolism studies due to highly effective separations, minuscule consumption of sample and reagents, compatibility with a variety of detection techniques, high-throughput via automation, and the implementation of on-line procedures. An on-line method comprised of the diffusion-based mixing of cytochrome P450 3A4 with racemic ketamine, incubation of the enzyme reaction, separation of the reaction products S-norketamine and R-norketamine and their quantification is presented in this chapter. Since diffusion is an inherent property of all molecules, this method enables the addition of virtually any compound to the reaction mixture without the need for additional optimization of the mixing conditions, and thus, can be favorably used for the rapid screening of putative cytochrome P450 3A4 inhibitors.