purgative vs medicinal drug

purgative and medicinal drug both are nouns.

Word	Noun	Adjective	Verb	Adverb
purgative	Yes	Yes	No	No
medicinal drug	Yes	No	No	No

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

purgative: a purging medicine; stimulates evacuation of the bowels
medicinal drug: (medicine) something that treats or prevents or alleviates the symptoms of disease

Other hypernyms of purgative include medicament, medication, medicine.

purgative (noun)	medicinal drug (noun)
a purging medicine; stimulates evacuation of the bowels	(medicine) something that treats or prevents or alleviates the symptoms of disease

purgative (adjective)	medicinal drug (adjective)
strongly laxative