Drugs And Receptors Flashcards
Define agonist
Drugs that bind to receptors and cause a response
Have affinity and efficacy
Equation for concentration?
Concentration (g/L) = MWt x molarity (M)
Define antagonists
Bind to receptors but don’t cause a response
Only have affinity
If a drug has a low Kd, what does this mean?
It has a high affinity
What does Kd mean?
The concentration required to occupy 50% of receptors.
How do we measure Kd?
Binding of a radioactively labelled ligand (radioligand) to cell membranes
What is Bmax?
The maximum binding capacity of a receptor
What do concentration response curves measure?
Response in cells or tissues
What does EC50 show?
The effective concentration giving 50% of a maximum response.
What can a response be?
A change in signalling pathway
A change in cell or tissue behaviour
What is Emax?
The maximum response
What type of drugs are used to treat asthma?
Beta agonists
What type of receptors are found in the airways?
Beta 2 and M3
Salbutamol:
Kd for β1 = 20mM
Kd for β2 = 1mM
Which one does it have a higher affinity for?
β2
What advantage are spare receptors?
Increase sensitivity, allowing responses at low concentrations of agonist
What factor does the number of receptors affect?
More receptors increases potency
What is a partial agonist?
A drug that cannot produce a maximal response, even with full receptor occupancy.
What is a clinical use of a partial agonist?
Morphine is an agonist. Buprenorphine is a partial agonist with a higher affinity but a lower efficacy. Provides adequate pain control with less respiratory depression.
What are the types of antagonists?
Reversible competitive antagonism
Irreversible competitive antagonism
Non-competitive antagonism
What is IC50?
The concentration of an antagonist that gives 50% inhibition
What is irreversible competitive antagonism?
When the antagonist dissociates sloe elf or not at all.
With increased time or [antagonist], more receptors are blocked and non-surmountable
When does homologous desensitisation occur?
When the response from a single stimulated receptor population is reduced
When does heterologous desensitisation occur?
When response to other agonists become blunted after a single receptor has been continuously stimulated.
What is intrinsic efficacy?
A measure of the ability of the drug to activate the receptor
