Drug Receptor Interactions Flashcards
(21 cards)
What is definition of agonist?
A drug that binds to receptor + elicits biological response
What is definition of antagonist?
A drug that blocks action of agonist compound by binding to receptor without eliciting a biological response
What is definition of affinity?
Ability of drug molecule to bind to receptor site
What is definition of efficacy?
Ability of drug to elicit biological response from drug receptor interactions
What is definition of partial agonist?
An agonist drug that produces a biological effect but never the maximal of which tissue is capable
What is definition of inverse agonist?
An agonist drug that produces an opposing biological response to that observed by full agonist
What type of binding is reversible?
H bonding
Ionic bonds
VDWs forces
These are relatively weak, reversible binding dissociation
What type of binding is irreversible?
Covalent binding => stable strong bonds , irreversible binding poor dissociation
What is Ka?
Amount of drug to occupy 1/2 the number of receptors
Each drug has its own Ka
Ka is same as saying …..
Kd
Higher the Ka, the …… the affinity
Lower
Lower the Ka, the…… the affinity
Higher
What occurs in saturation binding experiments?
Need receptor population
Add increasing concentration of agonist
Measure how much the agonist binds to receptor of interest
Describe what the Satruation plot graph shows?
There are finite amount of receptor
Bmax=> max amount of receptors which can be bound to drug
Describe the experiment to determine efficacy?
Develop assay
Increase concentration of drug
What is EC50 mean?
Efficacy
Effective concentration giving 50% biological response which is used to compare drug potency (determined by affinity + efficacy)
Affinity (Ka) + efficacy (EC50) are ……..
Not equal
You don’t need full occupancy to give max response
Only small no. Of drug receptor interactions can produce biological effects
Describe the characteristics of partial agonists?
Present at receptors -high affinity but less efficacy
Reduces additive highs
Reduces withdrawal effects
Heroin induced highs are reduced in presence of partial agonists
What is competitive antagonism?
Receptor only bind either agonist or antagonist
A and Ant compete for same binding site
A and Ant both bind irreversibly
Raising the agonist can store agonist occupancy
This antagonism is said to be surmountable
In presence of Ant conc, the effect of curve is shifted to right
Shift to right is linearly related to [Ant]
What is non competitive antagonism?
Give an example
Ant binds to different site from agonist
Leads to conformational changes to active sites which blocks pharmacological effect of agonist
E.g. ketamine
What is irreversible antagonism?
Give an example
Ant binds irreversibly to either agonist or non agonist binding sites in receptor through covalent bonds
Reduces number of receptor the agonist can bind to
E.g. aspirin
