<P> In pharmacology the term agonist - antagonist or mixed agonist / antagonist is used to refer to a drug which under some conditions behaves as an agonist ( a substance that fully activates the receptor that it binds to ) while under other conditions , behaves as an antagonist ( a substance that binds to a receptor but does not activate and can block the activity of other agonists ) . </P>
what is the difference between an opiate agonist and antagonist
a substance that fully activates the receptor that it binds to a substance that binds to a receptor but does not activate and can block the activity of other agonists