Receptor theory Flashcards
EC50
concentration of ligand giving 50% of maximal response (receptor reserve)
Efficacy
measure of an agonists ability to generate a response
KD
concentration where 50% of the receptors are occupied
Affinity
ability of a ligand to bind to a receptor
Agonist
chemical that binds to a receptor and activates the receptor to produce a biological response
Partial agonist
have only partial efficacy at the receptor relative to a full agonist. EC50=Kd
pA2
molecular conc of a.agonist needed to produce a dose ratio of 2 (need double the agonist to produce the same response)
Dose-ratio
how many more times agonist is needed in the
presence of an antagonist
Potency
measure of drug activity expressed in terms of the amount required to produce an effect of given intensity
What affects potency?
Affinity
Efficacy
Spare receptors
What is chemical antagonism?
when the agonist is chemically altered by the antagonism, for example when the substances combine in solution. E.g heavy metals toxicity is reduced by chelating agents
What is pharmokinetic 1. antagonism?
there is a reduction in the amount of drug absorbed- e.g from the GI tract
What is pharmokinetic 2. antagonism?
when the drug/agonist is metabolised, by antibiotics/other drugs etc.
What is physiological antagonism?
The interaction of two drugs with opposing actions in the body
e.g. NA raises arterial blood pressure by acting on the heart and peripheral blood vessels, while histamine lowers arterial pressure by causing vasodilation
What is non-competitive antagonism?
does not compete with the agonist for the receptor site
