To obtain information on the metabolic behavior of the test item in different species determined by an in vitro test.
In vitro tests with liver microsomes, hepatocytes or enzyme preparations.
Metabolic stability tests are carried out by using in vitro systems containing typically hepatic preparations of different species. Mouse, rat, dog and human liver microsomes or hepatocytes are generally tested but enzyme preparations of other species can also be included.
The metabolic stability of a test item is determined in two steps. In the first trial preliminary data are collected as for the approximate metabolic conversion rate. Based on the results of the first trial the parameters (protein content, length of the incubation and sampling time-points, and number of parallels) of the main trial are defined and the main test performed. The concentration of the test item is measured by a LC/MS/MS method. (Samples of appropriate positive and negative control are analyzed as well).
The results of the LC/MS/MS analysis are then used for the calculation of the metabolic conversion (%) or the metabolic clearance values.