18. Pharmacodynamics Review Flashcards
What is a ligand?
A substance that can interact with a target protein or receptor
Can be endogenous or exogenous
What is an agonist?
A substance that binds to a receptor and activates the receptor to then produce a measurable biological response
What is an antagonist?
Ligands that have affinity for a receptor or target protein but do not produce a biological response
Block the effect of agonists
What is affinity?
A measure of the strength with which a ligand or drug binds to a receptor
Can also be thought of as the likelihood of how well a ligand will optimally fit the receptor
What is the parameter used to define affinity?
Kd (dissociation constant)
What is Kd?
The concentration of a ligand at which 50% of all available receptors are bound
Lower the Kd, greater the affinity
What is intrinsic efficacy?
Term used to describe the ability of a ligand to generate the active form of the receptor (R*)
What is ligand efficacy?
The ability of a ligand to cause a measurable biological response
What is the definition of potency?
The concentration of a drug that evokes 50% of its maximal response (Emax)
EC50 is used to represent this concentration
Lower the EC50, more potent
What is a partial agonist?
Ligands that evoke responses that are lower than the maximal response of a full agonist (have lower Emax)
Has lower intrinsic efficacy
How is highest intrinsic efficacy shown on a graph?
Highest curve
How is a drug with highest potency represented on a graph?
Lowest conc needed for EC50 - furthest left on graph
What are the 3 types of drug antagonists?
Reversible competitive
Irreversible competitive
Non-competitive antagonism
