CLEARANCE, TURNOVER TIME, AND VOLUME OF DISTRIBUTION☆

Abstract 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×Turnover time=Volume of distribution