Pharmacokinetics
Say it: far-muh-koh-kih-NET-iks
Pharmacokinetics is the study of how the body absorbs, distributes, metabolizes and excretes a drug, and how drug levels change over time.
Definition
What is pharmacokinetics?
Pharmacokinetics describes what the body does to a drug: how it gets in, where it goes, how it is chemically changed and how it leaves. The four processes are summed up as ADME. Absorption moves the drug from where it was given, such as the gut or a muscle, into the blood. Distribution carries it to the tissues and depends on blood flow, binding to plasma proteins such as albumin, and the ability to cross barriers like the blood-brain barrier. Metabolism, mostly by cytochrome P450 enzymes in the liver, usually turns it into more water-soluble products, and excretion removes it, mainly in urine or bile.
The field turns these processes into numbers, such as bioavailability, volume of distribution, clearance and half-life. Together they predict how high the concentration of a drug will rise after a dose and how fast it will fall, which guides the dose, the route and the dosing interval.
Age, genes, body size, pregnancy and kidney or liver disease all alter pharmacokinetics, so one dose can produce very different blood levels in different people. Its partner field, pharmacodynamics, deals with what the drug does to the body.
Word parts
Where does the word “pharmacokinetics” come from?
- pharmaco-
- drugGreek pharmakon
- kinetics
- motionGreek kinetikos, from kinein, to move
Practice it
Where you'll meet it
Related
Terms that go with it
- PharmacodynamicsPharmacodynamics is the study of what a drug does to the body: how it acts on its molecular target and how its effects vary with dose.
- Half-lifeHalf-life is the time it takes for the concentration of a drug in the blood, or its amount in the body, to fall by half.
- BioavailabilityBioavailability is the fraction of a drug dose that reaches the general circulation unchanged, along with how quickly it gets there.
- First-pass metabolismFirst-pass metabolism is the breakdown of an oral drug in the gut wall and liver before it reaches the general circulation, reducing how much survives.
- LiverThe liver is the largest gland and internal organ, lying in the upper right abdomen, where it makes bile, processes nutrients and clears toxins.
- KidneyThe kidneys are two bean-shaped organs that filter the blood to make urine, balancing the body's water, salts and acid and helping set blood pressure.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- OpenStax Pharmacology for Nurses, 2.2 Pharmacokinetics and Pharmacodynamics
- MSD Manual Professional: Overview of Pharmacokinetics
Last updated
Spotted a mistake? Tell us and we'll correct it.
Practice Pharmacology
Free pharmacology quizzes, with an explanation for every answer.
See the Quizzes