promethazine vs antiemetic drug

promethazine and antiemetic drug both are nouns.

Word	Noun	Adjective	Verb	Adverb
promethazine	Yes	No	No	No
antiemetic drug	Yes	No	No	No

As nouns, antiemetic drug is a hypernym of promethazine; that is, antiemetic drug is a word with a broader meaning than promethazine:

promethazine: antihistamine (trade name Phenergan) used to treat allergies; also an antiemetic used to treat motion sickness
antiemetic drug: a drug that prevents or alleviates nausea and vomiting

Other hypernyms of promethazine include antiemetic, antihistamine.

promethazine (noun)	antiemetic drug (noun)
antihistamine (trade name Phenergan) used to treat allergies; also an antiemetic used to treat motion sickness	a drug that prevents or alleviates nausea and vomiting