Separation of the enantiomers of phenprocoumon and warfarin by high-performance liquid chromatography using a chiral stationary phase. Determination of the enantiomeric ratio of phenprocoumon in human plasma and urine

The enantiomers of the chiral coumarin-type anticoagulants phenprocoumon, warfarin and p-chlorophenprocoumon were separated by high-performance liquid chromatography on a chiral stationary phase (Nucleosil-Chiral 2) and normal-phase conditions. Chromatographic peak identification was performed with authentic reference compounds of the enantiomers and on-line UV spectra comparison. This method was applied to the determination of the enantiomeric ratio of phenprocoumon in plasma and urine extracts from patients under racemic drug therapy. The limit of detection (50 and 80 ng/ml) and precision (less than 5%) of the method are adequate for pharmacokinetic and enantioselective disposition studies, respectively, of phenprocoumon. No racemization was detected during the extraction procedures.