pharmacodynamics Flashcards
what is kd and what does it mean?
equilibrium dissociation constant
measure of receptor affinity
the lower the kd the higher the affinity
the concentration at which half-maximal binding occurs is the Kd
drug effect is proportional to what?
number of receptors occupied
what are the four characteristic parameters of the log dose response curve
slope
efficacy
potency
variability
what is more important. efficacy or potency.
efficacy
that is because if a drug is less potent you can just give more of it. but if a drug is less efficacious it might never reach the maximal effect desired
what is therapeutic index
LD50/ED50
the higher the better
is it possible for side effects to occur at the same or lower doses than the desired effect?
yes and sometimes this is a risk patients take
benefits outweigh risks
are drugs specific ?
no
they are selective!!
that means they bind more selectively to some receptors versus others–> but this can have unwanted side effects
hyperreactive
individual responds to a drug at unexpectedly low doses
can antagonists be potent?
yes but they have no intrinsic activity
what is an inverse agonist
something that has negative intrinsic activity–> inhibits responses even in the absence of an agonist (negative antagonist)
do antagonist have efficacy?
yes they can have efficacy by doing some sort of drug effect but they lack drug action. == no efficacy at the receptor level
we only see the effect of an antagonist in the presence of an agonist !!
where does the LDR shift for a competitive antagonist
to the right
effects of noncompetitive antagonists>
drugs are very prolonged!
examples of noncompetitive antagonists
phnoxybenzamine – antagonist at alpha receptors
irreversible cholinesterase inhibitors –> organophosphate insecticides and echothiophate
Aspirin–> modifies the enzyme cyclooxygenase and irreversibly inhibits platelet aggregation
desensitization
prolonged exposure of a cell to an agonist causes it to lose its responsiveness to that agonist
pharmacodynamic tolerance
