Incorporation of pharmacokinetic and pharmacodynamic data into risk assessments.

Risk assessment methodologies are being updated to allow the inclusion of numerical values for variance in pharmacokinetic (PK) measures and pharmacodynamic (PD) processes related to toxicity. The key PK measures and PD processes are identified from the results of carefully conducted and adequately reported studies. In some instances, studies with humans are not possible, and so the development of data useful for human PK evaluations and on PD processes in vitro or in silico represent an alternative. These results can be integrated under physiologic, anatomic, and biochemical constraints of the intact body through physiologically based pharmacokinetic (PBPK) modeling. This manuscript presents the rational for and key considerations related to the inclusion of quantitative PK and PD data in assessing chemical risks.