From the Guidelines

Pharmacokinetics refers to the study of how a drug is absorbed, distributed, metabolized, and excreted in the body.

Absorption: the process by which a drug is taken into the body, which can be affected by factors such as gut wall transporters and first-pass metabolism 1
Distribution: the process by which a drug is transported to its site of action, which can be influenced by factors such as body composition and plasma protein binding 1
Metabolism: the process by which a drug is broken down in the body, which can be affected by factors such as liver function and enzyme activity 1
Excretion: the process by which a drug is eliminated from the body, which can be influenced by factors such as kidney function and drug interactions 1

Age: can affect drug absorption, distribution, and metabolism, particularly in older adults 1
Disease states: can affect drug metabolism and excretion, such as liver or kidney disease 1
Drug interactions: can affect drug absorption, distribution, metabolism, and excretion, and can lead to adverse effects or reduced efficacy 1

Optimizing drug therapy: understanding pharmacokinetics can help healthcare providers choose the most effective and safe drug regimen for a patient 1
Minimizing adverse effects: understanding pharmacokinetics can help healthcare providers predict and prevent adverse effects, such as drug interactions or toxicity 1

From the Research

Pharmacokinetics is the study of the absorption, distribution, metabolism, and excretion (ADME) of a drug 2, 3, 4, 5
It deals with what the body does to a drug, including the time course of environmental and endogenous compounds 4
The primary utility of pharmacokinetics is to study the process of absorption, distribution, metabolism, and elimination of drugs, which is fundamental for drug action 2

Clearance, volume of distribution, half-life, and bioavailability are four fundamental pharmacokinetic parameters 4
Understanding these parameters is essential for drug development and precision medication 3
Pharmacokinetic studies provide correlates that may guide drug dosage in humans, although interspecies differences can be a challenge 6

Pharmacokinetics is used to evaluate the time course of drug effects and to predict the behavior and safety of compounds in humans 6
It is also used to assess drug-drug interactions, including interactions between drugs and herbs, therapeutic biologics, and microbiota-mediated interactions 3
Mathematical modeling, including physiologically-based pharmacokinetic modeling, is used to describe pharmacokinetics and pharmacodynamics 3, 5