Viagra vs anti-impotence drug

Viagra and anti-impotence drug both are nouns.

Word	Noun	Adjective	Verb	Adverb
Viagra	Yes	No	No	No
anti-impotence drug	Yes	No	No	No

As nouns, anti-impotence drug is a hypernym of Viagra; that is, anti-impotence drug is a word with a broader meaning than Viagra:

Viagra: virility drug (trade name Viagra) used to treat erectile dysfunction in men
anti-impotence drug: drug to treat impotence attributable to erectile dysfunction

Other hypernyms of Viagra include virility drug.

Viagra (noun)	anti-impotence drug (noun)
virility drug (trade name Viagra) used to treat erectile dysfunction in men	drug to treat impotence attributable to erectile dysfunction