Principles of pharmacokinetics.

A compartmental representation of the body is often used to explain the principles of pharmacokinetics, where the compartments are purely hypothetical and bear no relationship to real tissues or organs. In recent years a more physiological approach has been emphasized. Differences in derived kinetic parameters, such as elimination half-life, volume of distribution and clearance, as a function of drug, patient and route of drug administration, are more easily understood when related directly to primary physiological variables, such as blood flow, enzyme activity and drug binding. In turn this allows a convenient conceptual framework for describing and predicting both unbound and total drug concentrations in many clinical situations.