03.01.1 Introduction to Pharmacodynamics

The two main branches of pharmacology are pharmacokinetics (“What the body does to the drug”) and pharmacodynamics (“What the drug does to the body”). Drugs are administered to have a beneficial effect. In order to have a beneficial effect, drugs need to cause changes in some of the body’s processes. These can be a physiological, biochemical or pathological processes (Figure 3.1).

Figure 3.1 Pharmacodynamics (Copyright QUT, Sheila Doggrell)

The initial step in pharmacodynamics is the binding to distinct sites. Although the body does not have any binding sites that were specifically designed for drug binding, it has lots of binding sites for endogenous compounds, and drugs can use these binding sites.