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BASIC PRINCIPLES-3
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What are 4 ways to regulate a receptor?
1- Desensitization
2- Internalization
3- Upregulation
4- Downregulation
What is desensitization?
Rapid and reversible
process that
desensitizes the tissue
to any more
agonist
interaction
True or false, desensitization is reversible
True
False
True
What is Internalization?
When receptors are
recycled
via endocytosis in response to an
agonist
Rapid cyling
allows for dephosphorylation and increases the rate of restoration of receptors
The
binding of beta-arrestin
in a beta-adrenergic receptors is an example of which type of receptor regulation?
Desensitization
This process occurs when the receptor is continuously activated from
hours to days
Down-regulation
What is down-regulation?
A
decrease
in the number of receptor molecules in response to an
agonist
It is
slow
and
not readily reversible
This process occurs when the receptor is continuously activated from
minutes to hours
Internalization
This process occurs when the receptor is continuously activated from
seconds to minutes
Desensitization
What is tolerance?
A
decrease in the effect
(intensity) of the response to a given dose of a drug
ALSO
A
depletion of substrates
required for downstream effects
This process occurs when the receptor is continuously activated
for several days
Up-regulation
What is up-regulation?
An
increase
in the number of receptors in response to
pharmacologic antagonists
or denervation
Efficacy refers to the ability of the drug to.....
....accomplish a specified effect
Potency reflects the amount of the drug.....
.....required to cause an effect
What two factors determine the approptriate dose of a drug?
1- max therapeutic efficacy
2- pharmacologic potency
Which line is the partial agonist?
B
Which drug is the most potent?
B (the lowest EC50 value)
Which drug(s) have the highest efficacy?
A, C, D (highest Emax)
Which drug(s) have the highest efficacy?
Potency
refers
to the ____ and the ____ values on the graded-dose response curve
EC50 (concentration)
ED50 (dose)
Potency of a drug
depends
on the _____ of the dug for binding to the receptor and the ______ of the
occupancy response coupling process
KD (affinity)
efficiency
What does the
clinical effectiveness
of a drug depends on what? (2)
Emax (max efficacy)
ability to reach the site of action
When choosing between 2 drugs for administration one must chose based on _____ instead of _____
effectiveness
potency
________ _________ determines the administered
dose
of a selected drug
pharmacologic potency
Drug efficacy in a patient will be determined by? (2)
1-
mode of interactions
with the receptor
2-
characteristics
of the receptor-effector system
What is the purpose of a
quantal dose-response curve
?
It shows the percentage of indiviuals who
exhibit a drug effect
(toxic, theraputic)
vs. log drug dose
_______ is the
drug dose
where 50% of individuals exhibit the specified
quantal effect
ED50 (median effective dose)
What is TD50?
Median toxic dose
which is the dose required to
produce a toxic effect
in 50% of the individuals
What is the LD50?
Median lethal dose
which is the
dose required to kill 50%
of the individuals
What does the
therapeutic index
measure?
The
estimate of the safety
of a drug
It's the
TD50/ED50 ratio
What is the significance of a small therapeutic window?
It means that the
drug is toxic
and the
levels must be monitored
in a patient
frequently
What does the
therapeutic window (therapeutic range)
measure?
Dosage range between the
minimum effective therapeutic dose
and the
minimum toxic dose
What are the 4 mechanisims known to contribute to
variation in drug responsiveness
?
1- alteration in
concentration at the receptor site
2- variation in
concentration of an endogenous receptor ligand
3- alterations in the
number of receptors
4-
changes in componets of response
distal to the receptor
What are the 3 mechanisims for
mediating the toxic and beneficial effects
of drugs?
1- mediated by the
same receptor-effector mechanisim
2- mediated by
identical receptors in different tissues
3-mediated by
different types of receptors
An unsatistfactory therapeutic response is attributed to the _______ ________ _______ that respond to and oppose the effects of a drug.
physiologic compensatory mechanisms
Author
dr.fizzle
ID
64083
Card Set
BASIC PRINCIPLES-3
Description
725
Updated
2011-02-06T19:08:18Z
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