antipsychotic drug vs major tranquillizer

antipsychotic drug and major tranquillizer both are nouns.

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

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

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

antipsychotic drug (noun)	major tranquillizer (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