Lecture 32 - Drugs Acting Through Receptors 2 Flashcards
What is potency?
Affinity
Efficacy
Do drugs with different potencies reach the same maximum?
Yes
What is the difference between a weak agonist and a full agonist?
Different efficacies:
Weak: little response in the cell
Full: full response in the cell
What is potency?
The amount of drug required to elicit a certain response
Draw a dose-response curve of two drugs with different potencies
:)
Will a weak agonist ever reach the maximum?
No
Will partial agonists ever reach the maximum?
No
What is intrinsic efficacy?
This is the ability of the ligand to elicit a response in the cell
It is a property of the drug
What is coupling in pharmacology?
Transduction
This is the relationship between the binding of the ligand to the receptor and the transduction pathway
The greater the coupling, …
the greater the intrinsic efficacy of the drug
Draw a stimulus-response curve for two drugs of different coupling efficiency
Lecture 31
Slide 8
Draw a concentration-response curve:
- one drug
- different numbers of receptors
Lecture 31
Slide 11
What is the ‘gold-standard’ B-adrenoceptor agonist?
Isoprenaline
What are the features of isoprenaline?
High intrinsic efficacy
Compare isoprenaline with prenalterol
Isoprenaline: high intrinsic efficacy
Prenalterol: modest instrinsic efficacy
Describe an instance of tissue-dependency of the agonist
Prenalterol
Has much less of a response in the gut than in the atria due to the receptor density
Describe an instance of disease-dependence of an agonist’s activity
Prenalterol
TIssue has been desensitised to Prenalterol.
Has much less of a response in failing heart than in healthy heart, due to receptor number
Isoprenaline is also less potent in the failing heart
What are the drug-dependent factors of potency?
I/ Affinity
II/ Efficacy
What are the tissue-dependent factors of potency?
I/ Number of receptors
II/ Coupling
What are the different types of antagonism?
I/ Chemical
II/ Functional
Mechanical
Describe an example of chemical antagonism
Protamine binds to heparin, neutralising it
What type of molecule is protamine?
A polycation
What is competitive antagonism?
This is when a molecule binds to the active site of a receptor, preventing a response
What is surmountable antagonism?
The antagonism can be overcome by adding more of the agonist
Concontration dependent antagonism
Describe the two sites that the agonist and antagonist act on in competitive antagonism
They act on the same site
Draw a concentration-response graph of a drug at a certain concentration when there is an antagonist present, and when there is no antagonist
Slide 28
Draw a dose-response curve of a drug when there is and isn’t an antagonist present
Slide 29
Is the maximum still reached in competitive antagonism?
Yes - if the concentration of the agonist is high enough
What is happening in non-competitive inhibition?
The antagonist is binding to an allosteric site, leading to a change in the shape of the active site
What is the reason for the difference between partial and full agonists?
Different functional groups
