Test 4 definitions Flashcards
Kon
the rate of association or binding of the ligand to the receptor to form the drug receptor complex
Koff
the rate of dissociation or unbinding of ligand from the receptor
ligand
refers to a drug or endogenous substance that binds to a receptor eliciting a cellular or systemic response
receptor
refers to the cellular macromolecule or macromolecular complex with which the drug or ligand interacts to elicit a response
acceptors
things drug interact with that do not directly cause any change in biochemical or physiological response but can alter the pharmacokinetics of a drug’s actions
kd
the equilibrium dissociation constant is equal to the ligand concentration at which 50% of total receptors are bound
fractional occupancy
fraction of total receptors that are occupied by a ligand, equal to [LR]/[R0]
Kd is ___ related to affinity
inversely
if you know the ligand concentration and the kd, you can
determine the percentage bound even though we do no know the number of receptors
receptor occupancy curve
x axis: log [drug]
y axis: receptor occupancy / percent bound
info it can yield:
Kd; Bmax; comparison of affinity
Response/effect curve (graded response curve)
x axis: log [drug] y axis: percent response info it can yield: EC50 Emax comparison of potencies
potency
inversely related to the drug concentration required to produce a defined effect or response; the lower the concentration needed to produce the effect, the more potent the drug
most potent drug
smallest x value
efficacy
ability of a drug to produce a response and is related to the number of drug receptor complexes formed
to compare efficacy of drugs, compare their
Emax values
a graded dose response curve
is achieved by repeatedly exposing a single subject to a progressively increasing doses of drug and measuring the effect
quantal dose response curve
plots the fraction of the population that responds to a given dose of a drug against the drug dose
therapeutic index
equal to the ratio of TD50 to ED50; the larger the ratio, the safer the drug
inverse agonists
selectively bind to the inactivated form of a receptor and shift the conformational equilibrium toward the inactive state; in systems that are non constitutiutively active, inverse agonists will behave like competitive antagonists
a prerequisite for an inverse agonist response is that
the receptor must have a constitutive (aka intrinsic or basal) level of activity in the absence of any ligand
an agonist
increase the activity of a receptor above its basal level whereas an inverse agonist decreases the activity below the basal level
the efficacy of a full agonist
by definition is 100%
neutral antagonist
0%
inverse agonist
less than 0%