antidiarrheal vs antidiarrheal drug

antidiarrheal and antidiarrheal drug both are nouns.

Word	Noun	Adjective	Verb	Adverb
antidiarrheal	Yes	No	No	No
antidiarrheal drug	Yes	No	No	No

As nouns, antidiarrheal and antidiarrheal drug are synonyms defined as:

antidiarrheal and antidiarrheal drug: a drug used to control or stop diarrhea

antidiarrheal (noun)	antidiarrheal drug (noun)
a drug used to control or stop diarrhea	a drug used to control or stop diarrhea