SUBSTRATE DEPLETION APPROACH FOR DETERMINING IN VITRO METABOLIC CLEARANCE: TIME DEPENDENCIES IN HEPATOCYTE AND MICROSOMAL INCUBATIONS

@article{Jones2004SUBSTRATEDA,
  title={SUBSTRATE DEPLETION APPROACH FOR DETERMINING IN VITRO METABOLIC CLEARANCE: TIME DEPENDENCIES IN HEPATOCYTE AND MICROSOMAL INCUBATIONS},
  author={Hannah M. Jones and J. Brian Houston},
  journal={Drug Metabolism and Disposition},
  year={2004},
  volume={32},
  pages={973 - 982}
}
  • H. Jones, J. Houston
  • Published 1 September 2004
  • Biology, Medicine
  • Drug Metabolism and Disposition
The substrate depletion method is a popular approach used for the measurement of in vitro intrinsic clearance (CLint). However, the incubation conditions used in these studies can vary, the consequences of which have not been systematically explored. Initial substrate depletion incubations using rat microsomes and hepatocytes were performed for eight benzodiazepines: alprazolam, clobazam, clonazepam, chlordiazepoxide, diazepam, flunitrazepam, midazolam, and triazolam. Subsequent predictions of… 
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End-product inhibition may be more prominent in microsomes (in particular for substrate depletion assays where metabolism tends to be more extensive); results suggest that this phenomenon may contribute to the observed variations in metabolism characteristics and intrinsic clearance (CLint) between hepatocytes andmicrosomes.
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It is shown the substrate-depletion approach can be used to estimate KM and Vmax using both human liver microsomes and recombinant P450s, and will aid in the understanding of dosages at which non-linearity may occur, but potentially aid predictions of likely clinical drug–drug interactions.
Prediction of Drug Clearance by Glucuronidation from in Vitro Data: Use of Combined Cytochrome P450 and UDP-Glucuronosyltransferase Cofactors in Alamethicin-Activated Human Liver Microsomes
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The applicability of combined cofactor conditions in the assessment of clearance for compounds with a differential contribution of P450 and UGT enzymes to their elimination is indicated, in particular for UGT2B7 substrates.
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The objective of this dissertation research was to determine the mechanism underlying the system-dependent clearance of midazolam, a high CLint drug that is the most widely used CYP3A4/5 substrate for both the in vitro and in vivo assessment of drug-drug interactions (DDIs).
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Novel approaches were employed to explore fundamental experimental processes and associated potential limitations of in vitro predictions of clearance, advancing the interpretation of the rate-limiting processes involved in intrinsic clearance measurements and could be critical for successful in vitro prediction.
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