Pharmacokinetics and pharmacodynamics are two important concepts in the study of pharmacology which deal with the human body and the administration of a drug. By definition, these two terms are essentially the opposite of each other.
Pharmacokinetics: In pharmacology, this is the study of the mechanisms and processes the body uses when interacting with a drug. Basically, it analyses what the body does to a drug.
Pharmacodynamics: In pharmacology, this is the study of how a drug behaves once it enters the body. So essentially, this considers what a drug does to the body.
Pharmacokinetics involves understanding the processes of absorption, distribution, metabolism and elimination, which vary depending on the type of drug being administered. All of these processes occur once a drug is taken. The concept of bioavailability is also tightly linked to pharmacokinetics. Bioavailability refers to how much of a drug finally reaches the target area of the body.
On the other hand, pharmacodynamics considers the interaction of drugs with their receptors. A drug can only produce a response once it binds to the correct receptor and this leads to pharmacological, behavioural and physiological effects. Drugs not only produce desired impacts, but they also cause unwanted effects, known as side-effects. Pharmacodynamics aims to understand all of these effects, along with other concepts related to a drugs interaction with the body, such as the dosage required to produce certain effects.
Pharmacokinetics and pharmacodynamics are two extremely integral concepts to the study of pharmacology and thus, it is critical to understand the different meanings of these terms.