System approaches in pharmacokinetics: II. Applications.

Pharmacokinetic system approaches mathematically describe a general property of a pharmacokinetic system without modeling in specific terms the kinetic processes responsible for the general property. Certain applications of the system approach including methods for evaluating drug delivery, drug distribution, drug secretion, and biotransformation in linear and nonlinear pharmacokinetics are presented and discussed. Linear system formulae for various mean time disposition parameters and a disposition decomposition-recomposition system approach for predicting drug levels when the drug clearance changes are presented and discussed. System approaches offer certain advantages over traditional approaches for many practical applications.