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Assay title "PK CIA" does not match the file name "PK In Vitro Stability". The metadata block may have been copied from another assay — owner confirmation needed. Source text contained mis-encoded characters, repaired on import.

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Cocktail Inhibition Assay (CIA): The potential of test compounds to inhibit human cytochrome P450 isoforms (mainly CYP1A2, 2C8, 2C9, 2D6 and 3A4) is investigated with human hepatocytes in suspension.

Test compounds (usually 5 µM) are mixed with a cocktail of CYP isoform-specific substrates (mainly phenacetin, repaglinide, diclofenac, dextromethorphan and midazolam) and incubated with hepatocytes in suspension for up to 1.5 h (co-incubation) or up to 3.5 h (pre-incubation) at 37°C to obtain clearance values. Clearance values are obtained by measurement of the substrate depletion via LC/MS analysis. As a control serves the incubation of substrate cocktail in the absence of the test compound.

Inhibitory effects are determined by comparison of the clearance values for the isoform-specific substrates in the presence and absence of a potential inhibitor in co- and pre-incubation (the latter for evaluation of time-dependent inhibition). Finally, clearance ratios are calculated.

A cocktail of standard inhibitors, specifically inhibiting a single CYP isoform, is always included.