Abstract
A simple and sensitive analytical method for the determination of a drug and its metabolites in plasma samples has been developed. The method is based on image analyses of radioactive thin layer chromatograms obtained by using a bioimage analyzer and an imaging plate. To simplify the determination using thin layer chromatography (TLC), a small volume of plasma sample was directly applied on the reverse phase layer of the dual phase TLC plate and developed toward the silica layer. The radioactive material could be sufficiently separated from degraded plasma proteins. Time course studies of plasma concentrations of indomethacin and its metabolites were performed after i.v. and p.o. administration of [14C]indomethacin to rats. Specific radioactivity of [14C]indomethacin used in the present studies was relatively low (about 1.5 MBq / mg). However, the volume of plasma required for each time point was only 20μl due to high sensitivity of the image analyzing system. A complete concentration-time curve including nine time points could be obtained from each rat in the present studies. Pharmacokinetic parameters of unchanged indomethacin in the plasma could, therefore, be calculated for each rat. Hence the present method allowed to reduce the number of animals required for the preclinical pharmacokinetic studies using small laboratory animals.
