blocker vs blocking agent

blocker and blocking agent both are nouns.

Word	Noun	Adjective	Verb	Adverb
blocker	Yes	No	No	No
blocking agent	Yes	No	No	No

As nouns, blocker and blocking agent are synonyms defined as:

blocker and blocking agent: a class of drugs that inhibit (block) some biological process

blocker (noun)	blocking agent (noun)
a class of drugs that inhibit (block) some biological process	a class of drugs that inhibit (block) some biological process
a football player whose responsibility is to block players attempting to stop an offensive play