DIRECT DETERMINATION OF UNBOUND INTRINSIC DRUG CLEARANCE IN THE MICROSOMAL STABILITY ASSAY
- 1 September 2005
- journal article
- research article
- Published by Elsevier in Drug Metabolism and Disposition
- Vol. 33 (9) , 1319-1324
- https://doi.org/10.1124/dmd.105.005033
Abstract
The microsomal stability assay is commonly used to rank compounds according to their metabolic stability. Determination of the unbound intrinsic clearance (CLin,u) is essential for the accurate comparison of compounds, since nonspecific binding to microsomes can lead to an underestimation of the microsomal clearance. In this study, a new method (linear extrapolation in the stability assay, LESA) was established, which allows direct calculation of CLin,u from microsomal stability data, without the need to independently determine the fraction of free (unbound) drug. The method was validated using nine drugs with different chemical structures and physicochemical properties. The CLin,u of these compounds was extrapolated from the intrinsic clearance values obtained at different concentrations of human liver microsomes and compared with that calculated by the conventional method, using microsomal intrinsic clearance values and the free fraction of drug determined by equilibrium dialysis, ultracentrifugation, or ultrafiltration. A good agreement was observed between the data generated by the LESA method and those determined by conventional procedures. The method was further evaluated using a published dataset for 10 additional drugs and found to yield intrinsic clearance data comparable to the previously reported values. LESA provides a convenient and rapid method to determine the influence of microsome binding on intrinsic clearance in a single assay.Keywords
This publication has 14 references indexed in Scilit:
- SUBSTRATE DEPLETION APPROACH FOR DETERMINING IN VITRO METABOLIC CLEARANCE: TIME DEPENDENCIES IN HEPATOCYTE AND MICROSOMAL INCUBATIONSDrug Metabolism and Disposition, 2004
- Typical and Atypical Enzyme KineticsPublished by Taylor & Francis ,2003
- Impact of Nonspecific Binding to Microsomes and Phospholipid on the Inhibition of Cytochrome P4502D6: Implications for Relating in Vitro Inhibition Data to in Vivo Drug InteractionsDrug Metabolism and Disposition, 2003
- The Influence of Nonspecific Microsomal Binding on Apparent Intrinsic Clearance, and Its Prediction from Physicochemical PropertiesDrug Metabolism and Disposition, 2002
- Drug-Drug Interactions Involving the Membrane Transport ProcessPublished by Taylor & Francis ,2001
- Predicting drug pharmacokinetics in humans from in vitro metabolism studiesBiochemical Society Transactions, 2001
- Development of a High Throughput Equilibrium Dialysis MethodJournal of Pharmaceutical Sciences, 2001
- Towards the Predictability of Drug-Lipid Membrane Interactions: The pH-Dependent Affinity of Propranolol to Phosphatidylinositol Containing LiposomesPharmaceutical Research, 1998
- Partitioning of Ionizing Molecules between Aqueous Buffers and Phospholipid VesiclesJournal of Pharmaceutical Sciences, 1995
- Protein Binding as a Primary Determinant of the Clinical Pharmacokinetic Properties of Non-Steroidal Anti-Inflammatory DrugsClinical Pharmacokinetics, 1987