Agonists And Dose Response Curves Flashcards
What do agonists and receptors form and give example
Agonist receptor complexes
Salbutamol and B2
Form camp
Bronchodilation
Why is dosage important in pharmacodynamics
Need a certain dose for an effect but also there’s a line between toxicity
What is plotted on a dose response curve
Agonist concentration/ dosage
Against response % of the body
What is a GRADED dose response curve
Response of a particular system (person or tissue) to an AGONIST CONC
What is a QUANTAL dose response relationship curve
Where the response of the population/all tissues included
Plotted against the dosage of AGONIST OR ANTAGONIST CONC
Why is the graph placed on log scale
To fit the maximum dosage response relationship
Much higher dose needed
What is the maximum response called regardless of dosage
Efficacy / eMAX
What does EC50 mean on a dose response curve
The concentration/dose needed to produce a 50% response
What does the lowest point on graph show
The threshold dose needed for response
Explain the 2 state hypothesis
First state is
Drug + receptor —-> complex
The forward binding to this is K1
Reverse (dissociation of drug to receptor) = K-1
Next state is
AR complex —-> activated
Reverse is inactivion of complex
What does the first state (forming complex) show
The occupancy and affinity of the drug and receptor
What does the second stage (activation) show and presume
Shows efficacy of the drug to form response
Suggests it’s either in the inactive stage or the active (only 2)
How would you measure specific drug binding to receptors
You would measure the max number of drug bound (saturation) - non specific drug binding
What is the max drug binding number called
to determine number of drugs bound - non specific drugs
Bmax
What is kD a measure of
Affinity
It is the equilibrium dissociation constant
How is the kD measured and what does it tell us (equilibrium dissociation constant)
K1 association / k-1 dissociation
The lower the kD = higher affinity
When can kD affinity be equal to EC50
It is the same as the EC50 ONLY when response is proportional to occupancy of receptors
Why can kD be used to identify drugs or receptors
Because the kD of a drug receptor complex is the same in any tissue and person
What is EC50 a better measure of than kD because response isn’t proportional to occupancy
Potency
What is potency and why is it the same measure as EC50
Potency is the dosage/ conc needed to produce an effect
If a drug has a high potency (low EC50) it means they produce a response even at a lower concentration
What is potency dependant on
Affinity of the drug
Efficacy of the drug (ability to activate)
Receptor density
What are spare receptors
The fact that the proportion between occupancy and response isn’t linear
Some receptors can produce a higher response even in lower numbers
Spare receptors are ones not needed
What is efficacy
Ability of an agonist to evoke a response in receptor
Maximum is regardless of the dose given
EMAX = max efficacy
What is a full agonist
An agonist with high efficacy
They have an incline to the active state despite concentration
