pharmacodynamics II Flashcards
what is a ligand
any chemical that can bind to a receptor
what is a full agonist
a ligand that binds a receptor & produces a maximal response
what is a partial agonist
a ligand that binds a receptor & produces a smaller maximal response
-partial agonists occupy all of the available receptors
effect of partial agonist on a full agonist
partial agonist can antagonize a full agonist
what is an inverse (reverse) agonist
produces a change opposite to other agonists
what is an antagonist
ligand that binds a receptor but does NOT produce a response
-prevents an agonist from binding
what is an allosteric modulator
binds near the agonist’s orthosteric binding site
-changes effectiveness of agonist
what is a positive allosteric modulator
increases effectiveness of agonist
what is a negative allosteric modulator
decreases effectiveness of agonist
what is a biased agonist
(functionally selective) ligand that recognizes & stabilizes a GPCR into a certain configuration
=can either be an agonist, inverse agonist, or antagonist (depending on signal pathway that’s activated)
what are constitutively active receptors
receptors that cause a cellular response when NOT bound by ligand
efficacy vs intrinsic efficacy
intrinsic efficacy: how much a drug molecule stimulates a receptor (doesn’t vary among tissues)
efficacy: intrinsic efficacy + total receptor concentration (varies among tissues)
what is the dose-response relationship, & how is it graphed
demonstrates ability of a drug to produce pharmacological response
y-axis: pharm. effect
x-axis: [drug]
what does an ideal dose-response graph look like
(linear dose-response effect)
= typical hyperbolic curve
what does a dose-response graph look like when the pharm. effect is plotted against log(dose)
(sigmoidal dose-effect curve)
= sigmoidal “S” curve
graded vs quantal dose-response effects
graded: when response continuously increases up to a max as dose is continuously increased
quantal: (all or nothing, yes/no data) plots fraction of population that responds to given dose against the dose
3 types of drug antagonism
-chemical antagonism
-functional antagonism
-competitive antagonism
what is chemical antagonism
agonist & antagonist interact -> renders agonist pharmacologically inactive
what is functional antagonism
(aka physiological antagonism)
the independent opposing actions of two drugs cancel each other out in the body
what is competitive antagonism
antagonist competes w agonist for its binding site on the receptor
2 types of competitive antagonism
-equilibrium competitive
-non-equilibrium competitive
potency vs efficacy
potency: dose required to produce given effect
efficacy: intrinsic property of drug; how “good” of an agonist the drug is (at producing effect)
what are spare receptors
receptors that are not occupied by agonist (bc response could be elicited by agonist not occupying all receptors)
what does a narrow therapeutic index of drug safety indicate
that the drug can produce toxic effects
