APPLICATION OF MICRODIALYSIS TO STUDY THE IN-VITRO METABOLISM OF DRUGS IN LIVER-MICROSOMES

Current methods for studying in vitro drug metabolism involve add-incu bate-separate-measure approach. Separation of the desired analytes req uires removal of protein which is typically accomplished by precipitat ion and centrifugation and extraction of the analytes into an organic phase.:The analysis scheme then becomes more complex resulting in a de crease in precision and an increase in assay time. Microdialysis sampl ing circumvents these problems by allowing researchers to sample the r eaction mixture periodically and obtain the complete metabolic profile . In the present study, microdialysis sampling was used to investigate Phase I metabolism of salicylic acid, diazepam and ibuprofen in rat l iver microsomes. The major metabolites of these drugs were profiled by LC. Michaelis-Menten enzyme kinetic parameters, K-m and V-max were ob tained for the formation of diazepam metabolites by both microdialysis and conventional microsomal incubations and were in good agreement wi th the values reported in the literature. This study shows that microd ialysis has considerable promise as a sampling technique for in vitro drug metabolism studies. By making minor modifications to the instrume nts, microdialysis can be applied to other in vitro systems such as is olated hepatocytes to study the Phase II metabolism or tissue slices t o study drug distribution. (C) 1997 Elsevier Science B.V.