The relationships between the time course of drug or compound concentration (Pharmacokinetics, PK) and the onset, intensity and duration of pharmacological effect (Pharmacodynamics, PD) form the basis for evaluation of the drug’s efficacy and potency (referred to as Quantitative Pharmacology) in preclinical animal models of disease and in human patients.

Determining PK/PD relationships for compounds early on in discovery programs help in a)progression of the optimum compound for advanced testing; b)prediction of efficacy and potency based on in vitro and PK data; c)prediction of efficacy in humans by extrapolation of preclinical PK/PD models; and most importantly in setting dose, regimen and duration in pre-clinical pharmacology studies and in humans.

The in vivo Pharmacokinetics (PK) and Pharmacodynamics (PD) of a compound or drug can be represented as mathematical models. Developing PK, PD or PK/PD models help in simulations of what-if scenarios such as prediction of quantitative pharmacological effect when a compound is given as single, two or three doses in a day, concentration-time profiles for different doses and regimens, time needed for complete efficacy.

Such simulations help in designing optimal experiments, selection of time points for collection of data, prediction of effect in long duration studies thus avoiding time consuming studies, and prediction of PK and PD profiles in human populations. Modelling and Simulation (M&S) is a powerful tool in drug discovery and development and is being increasingly sought by the regulatory authorities for decision making.