W8 - Antagonist Flashcards
What is an antagonist
a drug that binds to a receptor but does not activate it, blocking the action of an agonist
what is IC50
concentration of antagonist to reduce response by 50%
How can we measure antagonistic action of a drug
plot a concentration response curve to an agonist in presence of increasing antagonist concentration then form a dose ratio or schild plot
What is a dose ratio
it is the fold increase in agonist concentration needed to evoke a given response in presence of antagonist to produce the same ec50 value
how do we calculate a dose ratio
ec50 + antagonist / ec50 control
How can we calculate dose ratio in fractional occupanc
1 + (Antagonist concentration / KD)
how can we calculate kd in fractional occupancy
log (dose ratio - 1) = Log ([Antagonist]) - log (Kd)
What does a schild plot tell us
if an antagonist is competitive and if so an estimate for the affinity of it
what value denotes a competitive inhibitor on a schild plot
-1
what does it mean if schild slope does not equal 1
insurmountable antagonism present
multiple binding sites
pharmacokinectic effects
allosteric interactions
what is insurmountable antagonism
in the presence of the antagonist no matter how much agonist you add you will never elicit the maximum response
