Key Principles of Pharmacology

1. Introduction

Pharmacology is the study of how a medicine works, how the body responds to it, and the changes that occur over time. The two main areas of pharmacology are: pharmacokinetics and pharmacodynamics. These are explained in more detail below. Non-clinical pharmacological studies allow scientists to compare a medicine’s beneficial effects with its negative (toxic) effects. This comparison is important so that a thorough benefit-risk analysis can be made before proceeding to test the medicine in human studies. If the medicine does proceed to the clinical phase, data gathered during non-clinical pharmacology and toxicology studies help to determine the dosage of medicine given to volunteers in the first- in-human studies.

An overview display of the different components, playing a role in a medicines effect in the body, is given in the following graphs:

Figure.1: Schematic representation of the different components acting in human pharmacology and their classification. (adapted from ‘Introduction to Pharmacokinetics’, J. Scott Daniels, Vanderbilt Univ Medical Center, 2012).


When determining the effect a medicine has, the time course from administration to excretion plays an important role as does the interaction between dose administered, pharmacokinetics (influence on concentration) and pharmacodynamics (influence on the effect). The following schematic ‘From PK to PD’ depicts this interrelation. 

Figure. 2: Schematic quantitative representation of the interaction between PK – PD – time – effect after administration of a medicine (adapted from ‘Introduction to Pharmacokinetics’,  
J. Scott Daniels, Vanderbilt Univ Medical Center, 2012)