Physiologically based pharmacokinetic modeling: from regulatory science to regulatory policy.

Assessment of controllable sources of intra- and interpatient variability in drug response is of critical importance in the regulatory evaluation of new drugs.(1) Although determinants of response variability would ideally be understood and accounted for before approval of a new pharmaceutical product, this is rarely the case for all; clinical trials in specific populations that definitively test optimal dosing in patient management strategies are not routinely performed prior to drug approval.