Viagra vs sildenafil

Viagra and sildenafil both are nouns.

Word	Noun	Adjective	Verb	Adverb
Viagra	Yes	No	No	No
sildenafil	Yes	No	No	No

As nouns, Viagra and sildenafil are synonyms defined as:

Viagra and sildenafil: virility drug (trade name Viagra) used to treat erectile dysfunction in men

Other synonyms of Viagra include sildenafil citrate.

Viagra (noun)	sildenafil (noun)
virility drug (trade name Viagra) used to treat erectile dysfunction in men	virility drug (trade name Viagra) used to treat erectile dysfunction in men