purple heart vs Luminal

purple heart and Luminal both are nouns.

Word	Noun	Adjective	Verb	Adverb
purple heart	Yes	No	No	No
Luminal	Yes	No	No	No

As nouns, purple heart and Luminal are synonyms defined as:

Other synonyms of purple heart include phenobarbital, phenobarbitone, sodium thiopental.

purple heart (noun)	Luminal (noun)
a long-acting barbiturate used as a sedative	a long-acting barbiturate used as a sedative