Pharmacodynamics Flashcards
How do drugs exert effects?
Bind to a target (usually a protein e.g. G protein)
What is critical to determining drug a action?
Concentration of the drug around a receptor
What are the different concentrations compared to a mole? M mM MicroM nM pM
mM- 10-3M
MicroM- 10-6M
nM- 10-9M
pM- 10-12M
What do we consider drug concentrations in?
Moles
How do most drugs bind to receptors?
Reversibly
Associates and dissociates
What is a ligand?
A molecule or ion that binds specifically to a receptor
What do most drugs do?
Block binding of endogenous agonist
Or active a receptor
What must a receptor have to bind to a receptor?
Have affinity for it
Higher affinity means stronger binding
What does an antagonist do?
Binds but does no activate
What does an agonist do?
Bind and activate
What is efficacy?
The ability of a ligand to cause a measurable response
What does intrinsic efficacy mean?
Can activate the receptor
What kind of drugs do not have efficacy?
Antagonists
How do we measure drug- receptor interactions by binding?
Radioactive labelled Ligands
What is Bmax?
Maximum binding capacity
What is Kd?
50 percent occupancy of available receptors Dissociation constant Index of affinity Lower value is a higher affinity Obtained by radioligand binding
What does a high affinity make possible?
Binding at low concentrations
What is the drug concentration like on a graph?
Logarithm- fixed base raised to a particular number
What does a response of a drug require?
Efficacy
What could the response of a Drug be?
Change in the signalling pathway
Change in cell or tissue behaviour
What is EC50?
Effective concentration giving 50 percent of the maximal response
The potency
What is a dose?
Concentration at site of action unknown (in mg or mg/kg)
What is the concentration of a drug?
Known concentration of a drug at site of action
For a ligand to have potency what does it need?
Affinity
Intrinsic efficacy
Efficacy
Affinity+efficacy =potency
