Theories Of Drug Action Flashcards
What are the super families of receptor and the duration of their action?
Ligand gaffe ion channels ms
G protein coupled receptors sec-min
Catalytic receptors min-he
Nuclear receptors hr-day
Define affinity
They ability of a drug to bind to its receptor
Define efficacy
The ability of a drug node bound to activate its receptor by a conformational change
What does the law of mass action state?
Rate of binding is proportional to concentration
Drug binding obeys this law
Forward reaction = Kon (association rate constant)[D][R]
Reverse reaction = Koff (dissociation rate constant) [DR]
What happen at equilibrium?
Forward reaction = reverse reaction
Kd (equilibrium constant) = [D][R]/[DR]
What is KD?
Concentration of drug needed to occupy 50% of the receptors at equilibrium
What are CE50 and Rmax?
R max is the max response a drug can generate at its receptor
EC50 is the effective concentration of agonist for 50% of its max response. It measures the agonist potency.
How does one measure potency?
Compare EC50 value
How does one measure efficacy?
Comparing Rmax value
What are EC50 and Rmax values determined by?
Drug-receptor interaction (affinity and efficacy)
Properties of the functional response (amplification)
How do competitive antagonists act?
They act by reducing the EC50 without affecting the Rmax
Eg: propranolol antagonises formoterol
How do non-competitive antagonist act?
Reduce Rmax and EC50
eg: glutamate ionotropic NMDA receptor antagonised by memantine (treat AD)
No structural similarities
Effect non-surmountable
