M&R Session 8- Receptors And Drug-receptor Interactions Flashcards
Do agonists have efficacy or affinity?
Both.
What are agonists?
They bind to receptors and cause a response.
What are antagonists?
Drugs that bind to receptors but don’t cause a response.
Do antagonists have efficacy or affinity?
Affinity only.
What do antagonists do?
They prevent agonists from binding to receptors and therefore prevent receptor activation by agonists.
What is intrinsic efficacy?
The ability to produce an active form of a receptor ligand complex.
What is efficacy?
The ability to produce a desired/intended response.
Determined by cell and tissue factors.
Why does an antagonist not produce a response?
Because it has no intrinsic efficacy, therefore cannot activate the receptor.
What is Kd?
The amount of ligand required to achieve 50% occupancy of available receptors.
What does a small Kd represent?
A high affinity. It means that less drug is required to achieve 50% occupancy.
What is the relationship between Kd and affinity?
Inverse proportion
What does response require?
Drug efficacy
What is EC50?
The effective concentration that gives 50% of the maximum response.
When should the term dose and concentration be used with regard to drugs?
Concentration- when the concentration of the drug is known at the site of action.
Dose- when the concentration is unknown at the site of action.
What does potency depend on?
Affinity and intrinsic efficacy
What is potency?
It is a measure of drug activity.
Why is it important that receptors are selective and specific? E.g beta 2 adrenoreceptors when treating asthma?
So that the drug being used only acts in the beta 2 receptor in the airways and not on beta 1 receptors for example in the heart to cause increase force and rate of heart contraction.
Why do spare receptors exist?
Due to signal amplification
What is the advantage of having spare receptors?
Allows increased sensitivity and therefore responses at low concentrations of agonist.
When do receptor numbers tend to increase and why?
With low activity in order to increase sensitivity.
What are partial agonists?
Drugs that can’t produce a max response even when receptors are fully occupied.
Give an example of a partial agonist and what it is used for.
Opioids,
Pain relief and recreational use (heroin) for euphoria
When can a partial agonist become a full agonist and why?
When the receptor number is increased because although each agonist has a low intrinsic activity at each receptor, there are sufficient receptors to produce a full response.
What is IC50?
The concentration of antagonist giving 50% inhibition.
