antipsychotic agent vs major tranquilizer

antipsychotic agent and major tranquilizer both are nouns.

Word	Noun	Adjective	Verb	Adverb
antipsychotic agent	Yes	No	No	No
major tranquilizer	Yes	No	No	No

As nouns, antipsychotic agent and major tranquilizer are synonyms defined as:

antipsychotic agent and major tranquilizer: tranquilizer used to treat psychotic conditions when a calming effect is desired

antipsychotic agent (noun)	major tranquilizer (noun)
tranquilizer used to treat psychotic conditions when a calming effect is desired	tranquilizer used to treat psychotic conditions when a calming effect is desired