drug receptor interactions 1 and 2 Flashcards
what is the KD?
Equilibrium dissociation constant
the concentration of drug required to occupy 50% of the receptors (the lower the KD, higher the affinity)
how do you calculate the fractional occupancy of a drug?
[D]/[D] + Kd
how do you calculate the pD2?
pD2= -log10 (KD)
what is pD2 a measure of?
affinity
what is efficacy a measure of?
the response elicited by the binding of a receptor to a drug
what are spare receptors?
if less than 100% of receptors are required to evoke a maximum response, the the receptors left over are ‘spare receptors’
what is the KA?
the equilibrium dissociation constant for an antagonist - concentration of antagonist which makes it necessary to add twice as much agonist to produce a response as would be needed in the absence of the antagonist
what is r in terms of the Schild equation?
the ratio by which [D] must be increased to overcome [A] (A=antagonist)
r=([A]/Ka) + 1 to reach 100% response rate
what is pA2?
affinity of an antagonist
pA2= -log10(KA)
what is a partial agonist?
an agonist that doesn’t elicit a full response on binding to a receptor
what is a competitive antagonist?
a drug which REVERSIBLY binds to a receptor but does not evoke a response - maximum response achieved but at a higher concentration of drug
what is an irreversible competitive antagonist?
a drug which IRREVERSIBLY binds to a receptor but does not evoke a response - maxim response to agonist decreased slowly with addition of more agonist
what are inverse agonists?
drugs which reduce the level of receptor activation
