Primary hepatocyte cultures as an in vitro experimental model for the evaluation of pharmacokinetic drug-drug interactions.

Publisher Summary This chapter describes the use of primary hepatocytes in the evaluation of pharmacokinetic drug-drug interactions. Two major mechanisms of pharmacokinetic drug-drug interactions are the inhibition and the induction of metabolic clearance. Inhibition of metabolic clearance may increase the plasma/tissue level to that with significant toxic consequences. Conversely, enhancement of metabolic clearance may lower the plasma/tissue level to that which is below the therapeutic level. Human in vitro systems with a complete set of CYP MFO isozymes, especially those derived from the liver, are now in use in many laboratories as preclinical experimental models. Hepatocytes may be isolated and cultured as primary cultures, and procedures for the isolation of hepatocytes are well-established. Most laboratories employ a two-step collagenase perfusion procedure. After isolation, hepatocytes may be used as suspension cultures for short duration studies or as attached cultures for longer-term studies. In suspension, hepatocytes rapidly lose viability. As attached cultures, hepatocytes remain viable for weeks. Most investigators culture hepatocytes on collagen-coated surfaces. Pharmacokinetic drug-drug interactions, the effects of one drug on the metabolic clearance of other coadministered drugs, are an important aspect of drug development. The two important mechanisms of drug–drug interactions are inhibition and induction of CYP450 isozymes. Storage of hepatocytes as cryopreserved cells is highly desirable for animal species such as human, where availability is limited. It has been concluded that cryopreservation is possible though not yet highly reproducible. The advantages of using hepatocytes stem from the use of an intact cell system that has essentially all of the xenobiotic metabolic pathways that are present in the liver in vivo.