mannitol vs diuretic drug

mannitol and diuretic drug both are nouns.

Word	Noun	Adjective	Verb	Adverb
mannitol	Yes	No	No	No
diuretic drug	Yes	No	No	No

As nouns, diuretic drug is a hypernym of mannitol; that is, diuretic drug is a word with a broader meaning than mannitol:

mannitol: a diuretic (trade name Osmitrol) used to promote the excretion of urine
diuretic drug: any substance that tends to increase the flow of urine, which causes the body to get rid of excess water

Other hypernyms of mannitol include diuretic, water pill.

mannitol (noun)	diuretic drug (noun)
a diuretic (trade name Osmitrol) used to promote the excretion of urine	any substance that tends to increase the flow of urine, which causes the body to get rid of excess water