Study of the body’s handling and metabolism of drugs in the body, including their absorption, distribution between different tissues, localization within tissues, modification and excretion (see: ‘ADME‘).
Drug activity depends on engagement between a drug and its molecular target. If the body does not absorb a drug, modifies it chemically, or rapidly excretes it, the drug will be less able to bind to its target site and have a biological effect.
Broadly speaking, pharmacokinetics considers the effect of the body on a drug, while pharmacodynamics considers the properties of a drug that affect target engagement in the body.
Population PK modelling takes account of variation in how drugs are metabolized by different people within a population. This requires more sophisticated statistical methodologies but provides results more relevant to individuals.
Physiologically-based pharmacokinetic models are more closely based on human anatomy, physiology and biochemistry. They are complex multi-component models that more accurately reflect human biology but are also more challenging to develop.