02.05.1 Introduction

When using drugs as therapeutics, the aim is to produce a specific effect. In most cases, to achieve this it is necessary to get the drug into the plasma at concentrations high enough to produce the effect.  However, it is also important not to administer too much drug, as this could lead to a range of non-specific toxic effects.  As can be seen in Figure 2.9, the ideal plasma concentration range is between the minimum concentration required to be effective (minimum effective concentration or MEC) and the concentration, above which toxic effects are seen (minimum toxic concentration). 

Figure 2.9 Minimum effective and toxic concentrations (Copyright Monash University, Liz Davies)

Graphs are used to describe the relationship between blood levels of drugs over time.  From these graphs, we can learn things about drugs that help us to determine how to use them in people.