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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
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?
This process occurs when the receptor is continuously activated from hours to days
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
This process occurs when the receptor is continuously activated from seconds to minutes
What is tolerance?
A decrease in the effect (intensity) of the response to a given dose of a drug
A depletion of substrates required for downstream effects
This process occurs when the receptor is continuously activated for several days
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?
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
Potency of a drug depends on the _____ of the dug for binding to the receptor and the ______ of the occupancy response coupling process
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 _____
________ _________ determines the administered dose of a selected drug
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