sedative-hypnotic vs downer

sedative-hypnotic and downer both are nouns.

Word	Noun	Adjective	Verb	Adverb
sedative-hypnotic	Yes	No	No	No
downer	Yes	No	No	No

As nouns, downer is a hypernym of sedative-hypnotic; that is, downer is a word with a broader meaning than sedative-hypnotic:

sedative-hypnotic: a sedative that depresses activity of the central nervous system and reduces anxiety and induces sleep
downer: a drug that reduces excitability and calms a person

Other hypernyms of sedative-hypnotic include depressant, sedative, sedative drug.

sedative-hypnotic (noun)	downer (noun)
a sedative that depresses activity of the central nervous system and reduces anxiety and induces sleep	a drug that reduces excitability and calms a person