Pharmacodynamics
Say it: far-muh-koh-dy-NAM-iks
Pharmacodynamics 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.
Definition
What is pharmacodynamics?
Pharmacodynamics studies the effects of drugs and the mechanisms behind them, often summed up as what a drug does to the body. Most drugs act by binding to a target molecule, usually a receptor, enzyme, ion channel or transporter, and changing its activity. How strong the effect is depends on how much drug reaches that target.
A few ideas sit at the center of the field. Affinity is how readily a drug binds its target, and efficacy is how strongly it activates the target once bound. Agonists bind and activate receptors, while antagonists bind without activating them and block other molecules. Potency reflects how much drug is needed for a given effect. These relationships are drawn as dose-response curves, which also reveal the gap between a helpful dose and a harmful one, the therapeutic index.
Responses vary between people because disease, age, genes and other drugs can change the number or sensitivity of receptors. Repeated use can bring tolerance, in which a larger dose is needed for the same effect. Pharmacodynamics pairs with pharmacokinetics, which follows the movement of a drug through the body.
Word parts
Where does the word “pharmacodynamics” come from?
- pharmaco-
- drugGreek pharmakon
- dynamics
- power, forceGreek dynamis
Practice it
Where you'll meet it
Quizzes that use it
Related
Terms that go with it
- PharmacokineticsPharmacokinetics is the study of how the body absorbs, distributes, metabolizes and excretes a drug, and how drug levels change over time.
- ReceptorA receptor is a protein, on a cell's surface or inside it, that binds a specific signaling molecule and triggers a response in the cell.
- AgonistAn agonist is a drug or natural substance that binds to a receptor and activates it, producing a biological response.
- AntagonistAn antagonist is a drug that binds to a receptor without activating it, blocking the natural signal or an agonist from producing an effect.
- Dose–response curveA dose–response curve is a graph showing how the size of a drug's effect changes as its dose or concentration increases.
- Therapeutic indexThe therapeutic index is a ratio comparing the dose of a drug that causes toxicity with the dose that produces the desired effect.
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 Pharmacodynamics
- MSD Manual Professional: Drug-Receptor Interactions
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