Determination of a human hepatic microsomal scaling factor for predicting in vivo drug clearance.

Purpose: To determine a microsomal scaling factor for human liver suitable for prediction of in vivo drug clearance from in vitro data and to explore the role of inter-liver variability in this factor on the reported underprediction from microsomal parameters.

Methods: Cytochrome P450 (henceforth P450) content in whole homogenates and microsomes from 38 donor livers was used to determine a microsomal scaling factor. In a subset (n = 20) of these preparations, individual P450 enzymes were examined by Western blotting and selective probe activities were determined.