Achiral and chiral HPLC analysis of norverapamil and its metabolites in microsomal samples

Achiral and chiral HPLC (high performance liquid chromatography) were developed for monitoring norverapamil and its two metabolites in in vitro microsomal samples. Norverapamil is a chiral drug with the same ability as verapamil in reversing MDR (multi-drug resistance) against some cytostatics. R(+) norverapamil is less cardiotoxic as S(-) enantiomer and so it could be applied in higher concentrations. HPLC conditions were worked out for both achiral and chiral assays and very simple and effective preseparation procedure (SPE - solid phase extraction) was used for microsomal sample as clean-up step before HPLC analysis. The total concentrations of norverapamil and its metabolites were calculated from achiral chromatograms and the ratio of enantiomers were determined from chiral separations. The complete assay could be used for both in vitro and in vivo experiments.