Clearance, turnover time, and volume of distribution.

In mathematics a parameter is a fixed quantity that determines the behavior of a function. In the experimental sciences a parameter is an observable quantity that remains constant for every definable state of a system. In pharmacology it is important to distinguish among pharmacokinetic parameters, model parameters, and incidental parameters. A pharmacokinetic parameter is a quantity that defines a pharmacokinetic property of a biologic entity; conversely a model parameter defines the property of a chosen model, and an incidental parameter defines only the result of an experiment. The three most important pharmacokinetic parameters are clearance, turnover time, and volume of distribution. They are related by the expression. Clearance x Turnover time = Volume of distribution.