Block A Sem 1 Flashcards
Define Affinity
The property of a drug to bind to a binding site
Define Efficacy
A measure of the ability of an agonist to activate the receptor and produce a response
Define Agonist
Drugs or naturally occurring body substances which cause a measurable response
What does Emax refer to?
The maximum response an antagonist can produce in a specific setting
Define each symbol in this equation
Pa=Xa/Xa+Kd
Pa= Proportion of receptors occupied
Xa= Concentration of agonist
Kd= Affinity of agonist
What is the result of a Pa being 50%
The Kd (affinity of agonist) is equal to the concentration of the agonist
What is a partial agonist
An agonist that is unable to reach maximal response due to low efficacy
What is an inverse agonist?
Agonists with negative efficacy
Name some inverse agonists
ziprasidone- atypical antipsychotic
Naloxone- Used in opiate overdose
what is a biased agonist?
An agonist which only inhibits one portion of the signaling pathway, inhibiting the other
Define Chemical antagonism
When one drug antagonises another by chemically combining with it
Define Physiological antagonism
When two drugs counteract each other by producing opposite effects
Define pharmacological antagonism
When antagonists bind to a receptor and stops an agonist binding
Explain what the symbols in this equation mean. Kb=Xb/r-1
Kb= Antagonist dissociation constant
Xb= Antagonist concentration
r= Dose ratio
What is the result of a dose ratio being equal to 2 in this equation, Kb=Xb/r-1?
Antagonist dissociation constant is equal to antagonist concentration
What is irreversible competitive antagonism?
Insurmountable antagonism often due to covalent bonding
What is non-competitive antagonism?
Antagonism where an allosteric binding site is used to alter the structure of the binding site so the agonist may not fully bind
What is radioligand binding?
Can you suggest examples?
A radioactively labelled drug that can associate with any site of interest.
[3H]-salbutamol/mepyramine/adrenaline
What information would a radioligand reveal?
Number of binding sites
Affinity to binding sites
Where the binding sites are
