ABSTRACT
Pharmacodynamics (PD) can be defined as the quantitative relationship between plasma and/or tissue concentration(s) of the active moiety and the magnitude of the pharmacological effect(s); this is in contrast to pharmacokinetics (PK), which describes the quantitative relationship between administered doses and dosing regimens and plasma and/ or tissue concentrations of the drug. This chapter deals with the characterization of PK/PD models describing the action of drugs that specifically and reversibly interact with biological receptors and induce measurable pharmacological effects. PK/PD modeling allows the estimation of PK/PD parameters and the prediction of these derived, clinically relevant parameters, as well; PK/PD simulations allow the assessment of the descriptive parameters as functions of dose and dose rate. Different drugs are characterized by different PK and PD models and/or by differences in their intrinsic model parameter values, e.g., volume of distribution, total body clearance, receptor affinity, intrinsic activity, etc.; understanding of the PK/PD model allows a rational comparison of pharmacological properties for different drugs.
