Phenprocoumon metabolites in human plasma; characterization by HPLC and GC-MS

Pooled plasma from patients receiving phenprocoumon anticoagulant therapy was extracted and the following substances were characterized: phenprocoumon, and its 7-hydroxy,4'-hydroxy and 6-hydroxy derivatives; they were identified by HPLC and after methylation by quartz capillary GC-MS using the electron impact and selective ion monitoring modes. This is the first occasion when phenprocoumon metabolites have been identified in plasma; they were unconjugated and in much lower concentrations (43.2 and 2 ng/ml for the 7,4' and 6-hydroxy derivatives, respectively) than the original compound (2000 ng/ml).