Pharmacokinetic Parameters/Variables

PHARMACOKINETIC PARAMETERS

The predictive capability of a pharmacokinetic model lies in the proper selection and development of mathematical functions called parameters that govern a pharmacokinetic process. In practice, pharmacokinetic parameters are determined experimentally from a set of drug concentrations collected over various times known as data. Parameters are also called as variables. Variables are of two types –

1. Independent variables which are not affected by any other parameter, for example time.

2. Dependent variables, which change as the independent variables change, for example, plasma drug concentration.

Certain points, which are important to note regarding application of parameters in pharmacokinetic studies, include –

^·            The number of parameters needed to describe the pharmacokinetic model depends upon the complexity of the pharmacokinetic process and on the route of drug administration.

^·            More the number of parameters more are the difficulties in accurate estimation of these parameters.

^·            For the pharmacokinetic parameters to be valid, the number of data points should always exceed the number of parameters in the pharmacokinetic model.