when a drug molecule moves so close to its receptor that the attractive force between them becomes great enough to overcome the random motion of the drug molecule, the drug binds to the receptor.
affinity
the affinity of a drug for a particular receptor and the type of binding that occurs ins intimately related to the drug's what?
chemical structure
because 2 drug molecules cannot occupy the same receptor site at the same time, the drug with the _______ _______ will bind more readily to the receptor
greater affinity
affinity is expressed by its __________ ________ (___) which is the concentration of a drug required in solution to achieve ___% occupancy of its receptors
dissociation constant
KD50
What happens when 2 drugs of equal concentrations are competing for the same receptor population?
the drug with the greater affinity will bind with more receptors (and stimulate the receptor to cause an action) at any given instant; and a lower concentration of that drug will produce the same level of pharmacologic effect
drugs with good affinity have greater _____ and require a _________ dose to cause a specific effect
potency
smaller
_________ is related to the affinity of a drug
potency
drugs that have direct stimulatory effects on receptors are called what?
agonists
a strong againist produces a significant physiologic response when a relatively _______ number of receptors are occupied
small
the ability of an agonist to interact with a receptor and initiate a response is the function of its what?
intrinsic activity
when a small dose of a drug (agonist) produces a desired effect, the drug has good _____ and good _________
affinity
intrinsic activity
true or false. a weak agonist must be bound to many more receptors to produce the same affect, so a musch larger dose of a weak agonist will be required to produce the desired affect. the drug has a lower affinity and/or lower intrinsic activity
both statements are true
a _______ ________ has affinity for the receptor, but very low intrinsic activity, and will never produce the same effect as a strong agonist or weak agonist even when all receptors are occupied.
partial agonist
the maximum response produced by a drug
efficacy
concept stating; a state of optimal receptor occupancy by the drug molecules; additional doses would produce no further beneficial effect
ceiling dose
as seen with the affinity of a drug for a particular receptor, the efficacy of a drug is also related to its ________________
chemical structure
The lowest dose of a drug that will produce a measureable response is called the what?
threshold dose
What is an example of a drug that reaches a plateau, efficacy, or maximal effect?
acetaminophen, which has a ceiling dose of 1,000 mg for pain reliev, taking more will not produce greater pain relief, and may lead to toxicity
the relative pharmacologic activity of a dose of a compound compared with a dose of a different agent producing the same effect
potency
__________ is related to the affinity of a drugy to its receptor, whereas _______ is related to the intrinsic activity of that drug once a drug receptor comlex is formed
potency
efficacy
_________ is used to compare the effect of 2 drugs with affinity for the same receptor, to produce a given effect as a function of dose
potency
a drug that interferes with the action of an agonist but has no effect in the absence of an agonist and can be classified as receptor or nonreceptor _______
antagonist
________ _________ prevent binding of agonist
receptor antagonists
What are 2 ways that a receptor antagonist can prevent agonists from doing their job?
they can bind at the active site (or binding domain) and prevent the binding of the agonist
they may bind to an adjacent site (overlapping with the agonist binding domain) and prevent the donfomational change required for receptor activation by an agonist
true or false. Receptor antagonism can be reversible (competetive) or irreversible (noncompetetive)
binds reversibly to the active site of tha agonist and maintains the receptor in its active conformation; it has affinity for a receptor, but no efficacy (cannot cause an effect)
competetive antagonist
how can the effect of a competetive antagonist be overcome?
increasing the dose of the agonist
the presence of a competitive antagonist reduces the ________ of the agonist
potency
binds to either the active site or to an allosteric (adjacent) site of the receptor and binds to the active site either covalently or with very high affinity, both of which are effectively irreversible
noncompetetive antagonist
true or false. an allosteric noncompetitive antagonist prevents the receptor from being activated even when the agonist is bound to the active site.
true
the presence of a noncompetitive antagonist reduces the ________ of the agonist
efficacy
what is an example of a noncompetitive antagonist?
