Pharmacokinetics describes the processes that underpin how the human body handles a drug. There are four elements to pharmacokinetics: absorption, distribution, metabolism, and excretion. Drug absorption involves the movement of the drug across a cell membrane and is largely dependent on diffusion. The absorption rate is determined by the preparation of the drug, route of administration, size of the molecule, concentration gradient, degree of protein binding and lipid solubility of the drug. First pass metabolism can be responsible for reducing the bioavailability of drugs via certain routes like oral administration.

Different compartment models can be used to predict the pharmacokinetic process of drug distribution. Multicompartmental models are used to understand how the drug is distributed to model the uptake of the drug into different tissues at varying rates. These models are utilized for targeted controlled infusions in practice to maintain anaesthesia at an effect site concentration that is specified by the user.