02.01 Introduction

After a drug has been administered and absorbed into the systemic circulation, it has to be distributed in the blood, to its site of action, where the pharmacodynamic process (mechanism of action, actions in the body) will take place. The drug is then usually metabolised and excreted. Distribution, metabolism and excretion are discussed in the following chapters. Absorption, distribution, metabolism and excretion are all important determinants of the plasma levels of drugs. The plasma levels of drugs are also discussed.