title: Stereospecific pharmacokinetic characterisation of phenprocoumon metabolites, and mass-spectrometric identification of two novel metabolites in human plasma and liver microsomes.
abstract: Phenprocoumon belongs to the group of vitamin K antagonists (VKAs), for example warfarin and acenocoumarol. It is widely used for therapeutic anticoagulation and clinically administered as a racemate. Both enantiomers are partially metabolized by the polymorphic CYP2C9 enzyme. The pharmacokinetics are, however, substantially less dependent on CYP2C9 activity or genotype than for other CYP2C9-metabolised VKAs, and pharmacokinetic differences for the enantiomers are only minor. We have investigated the stereospecific pharmacokinetics of the monohydroxylated phenprocoumon metabolites in human plasma by achiral-chiral LC-LC-MS-MS coupling. In addition to the known metabolites, 4'-, 6-, and 7-hydroxyphenprocoumon, two other monohydroxylated metabolites (M1 and M2) were detected in plasma and human liver microsomal incubations. One of these was identified as 2'-hydroxyphenprocoumon by comparison with synthetic standards; the other seemed to be a side-chain-hydroxylated derivative. Analysis of enantiomeric metabolite ratios after a single oral dose of phenprocoumon revealed changes over time with an overall preponderance of the respective (R) enantiomers. The minor role of CYP2C9 in 4'-hydroxy-PPC formation and the effect of CYP2C9 genotype for (S)-6- and (S)-7-hydroxy-PPC were confirmed. M1 and M2 are formed highly stereoselectively, without dependence on CYP2C9 genotype. These may be interpreted as alternative metabolic pathways that render phenprocoumon less dependent on CYP2C9 activity or genotype.
authors.affiliation: Institute of Pharmacology and Toxicology, Division of Clinical Pharmacology, University Hospital Tübingen, 72076 Tübingen, Germany. Bernd.Kammerer@uni-tuebingen.de
authors.forename: Bernd
authors.initials: B
authors.lastname: Kammerer
authors.forename: Rainer
authors.initials: R
authors.lastname: Kahlich
authors.forename: Mike
authors.initials: M
authors.lastname: Ufer
authors.forename: Andreas
authors.initials: A
authors.lastname: Schenkel
authors.forename: Stefan
authors.initials: S
authors.lastname: Laufer
authors.forename: Christoph H
authors.initials: CH
authors.lastname: Gleiter
mesh_terms: D000925:Anticoagulants / Q000737:chemistry; D019540:Area Under Curve; D001189:Aryl Hydrocarbon Hydroxylases / Q000378:metabolism; D065729:Cytochrome P-450 CYP2C9; D006801:Humans; D006900:Hydroxylation; D013058:Mass Spectrometry; D008862:Microsomes, Liver / Q000737:chemistry* / Q000201:enzymology; D010644:Phenprocoumon / Q000031:analogs & derivatives* / Q000097:blood / Q000737:chemistry* / Q000378:metabolism; D013237:Stereoisomerism
chemical_list: D000925:Anticoagulants; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases; D010644:Phenprocoumon