major tranquillizer vs antipsychotic agent

major tranquillizer and antipsychotic agent both are nouns.

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

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

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

major tranquillizer (noun)	antipsychotic agent (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