pep pill vs stimulant drug

pep pill and stimulant drug both are nouns.

Word	Noun	Adjective	Verb	Adverb
pep pill	Yes	No	No	No
stimulant drug	Yes	No	No	No

As nouns, stimulant drug is a hypernym of pep pill; that is, stimulant drug is a word with a broader meaning than pep pill:

pep pill: a central nervous system stimulant that increases energy and decreases appetite; used to treat narcolepsy and some forms of depression
stimulant drug: a drug that temporarily quickens some vital process

Other hypernyms of pep pill include drug of abuse, street drug, excitant, stimulant.

pep pill (noun)	stimulant drug (noun)
a central nervous system stimulant that increases energy and decreases appetite; used to treat narcolepsy and some forms of depression	a drug that temporarily quickens some vital process