Receptor theory and pharmacokinetics Flashcards
What is efficacy
A measure of a single agonist receptor complex’s ability to generate a response
What is the efficacy of an antagnoist
0
What is the efficacy of an agnonist
1
What is the concentration of a dug and the size of the response measured using
A bioassay using isolated cells
What does EC50 show
Defines the relationship between the drug and the response in that tissue
What is receptor reserve
100% of receptors don’t need to be occupied to give maximal response
Why is receptor reserve useful
Because the amount of hormones needed can be much lower
Which direction do spare receptors shift the response curve to
To the left of the binding curve
What will the efficacy of the agonist for its receptor influence
It will influence how big and how well it can produce responses
What is the hill slope equation
Response = max[Xa]^n/ ([Xa)n+[EC50]^n)
n is the hill slope factor, measure of the number of molecules that need to bind to a receptor to activate it
What does the drug with the highest potency require
The lowest concentration to produce 50% maximal response
What does the location of the concentration response curve depend on
Affinity, efficacy and spare receptors
What do agonists with different efficacies produce
Different maximal responses
What efficacy does a partial agonist have
between 0-1
What are partial agonists not able to produce
Not able to produce the same maximum response as a full agonist
What does a partial agonist need to achieve to produce the maximum response that it’s capable of?
100% occupancy
What are equal for partial agonists and why is this desirable
KD and EC50. You can’t get a maximum response for partial agonists so you can’t overdose
What 3 properties determine the effect of a drug in a living system
Specificity, affinity and efficacy
Definition of an antagonist
A drug that prevents the response of an agonist
What 5 classes can antagonism be divided into
Chemical, pharmacokinetic, physiological, non-competitive and competitive
What happens in chemical antagonism
Substances in a solution combine so that the effects of the active drug are lost
Example of chemical antagonism
Inactivation of heavy metals reduced with the addition of a chelating agent
What happens in pharmacokinetic antagonism
Refers to the processes that control the concentration of drugs in the body
Example of pharmacokinetic antagonism
some antibiotics stimulate the metabolism of warfarin so reducing its effective concentration in the blood stream