Pharmacodynamics II Flashcards
what are the assumptions we make with quantitation of drug action?
drug effect is proportional to the fraction of receptors occupied
maximal effect results when all receptors are occupied
what is a graded dose-response?
dose-dependent intensity of an effect
what is a quantal dose response?
dose-dependent specified effect in number of patients
what is KD- the dissociation constant?
the concentration at which 50% of binding sites are occupied by the drug
what does the height of the graded dose-response curve correlate to?
maximal effect, efficacy
is efficacy or potency more important therapeutically?
efficacy
true/false: potency and efficacy are unrelated
true
what are partial agonists?
drugs that bind to and activate a given receptor, but only have partial efficacy at the receptor relative to a full agonist
why would KD not equal ED50?
spare receptor concept
if there are spare receptors, could have 100% of effect without binding them all (two are on one action)
if there are fewer receptors, could have 25% of effect
considering the receptor theory, what is the term for the concentration of a drug at which 50% of receptors for that drug are occupied by the drug?
KD, dissociation constant
how do competitive/reversible antagonists affect the dose-response curve?
decrease affinity
efficacy unaffected
rightward shift: more drug to get same effect
how do non-competitive/irreversible antagonists affect the dose-response curve?
affinity unaffected
efficacy decreased
downward shift: once non-competitive binds, it won’t let go so effectively decreased the binding sites
_____________ exacerbate physiological responses
_____________ inhibit physiological responses
agonists
antagonists
how do antagonists produce their effects?
competing with an agonist for a receptor
irreversibly blocking the receptor
what is the equation for the therapeutic index?
TI=TD50/ED50
TD50= toxic dose in 50% of the subjects
