|Simultaneous Characterization of Warfarin, Hydroxywarfarins, and Warfarin Glucuronides in Human Urine|
|Mon 4:30 PM - Session: Environment and Chemical Disaster|
|Despite significant progress elucidating the role of Phase I Cytochrome P450s in warfarin (Coumadin) hydroxylation, understanding contributions of Phase II enzymes is lacking. To address this gap in knowledge, we are investigating the ability of Phase II UDP-glucuronosyltransferases (UGTs) to conjugate warfarin and hydroxywarfarins (OH-war) with glucuronic acid.
Studies with recombinant UGTs show that hepatic UGT1A1 and 1A9 and extrahepatic UGT1A3, 1A8, and 1A10 glucuronidate 6-, 7-, and 8-OH-war to various extents (Zielinska et al (2008) J Pharmacol Exp Ther 324:139-48.). Nevertheless, the physiological significance of this metabolic pathway remains unclear.
This study describes HPLC-MS/MS assays which are capable of simultaneously measuring warfarin, hydroxywarfarins, and glucuronidated metabolites of warfarin. The diasteromer method is rapid (< 7 min), sensitive (MDL ? 1 nM), and capable of quantitatively measuring low (10 nM) and high (100 nM) concentrations of these compounds in human urine. The enantiomeric method separates and measures the relative contribution of each enantiomer of warfarin (R/S), hydroxywarfarins (R/S), and the glucuronidated metabolites of warfarin (R/S) without losing precision, accuracy or sensitivity. Analysis of urine specimens received from female patients (F84, F85, F87) on warfarin therapy revealed that Phase I P450 and Phase II UGT products are excreted at high concentrations (nM to