antihistamine vs medicinal drug

antihistamine and medicinal drug both are nouns.

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

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

antihistamine: a medicine used to treat allergies and hypersensitive reactions and colds; works by counteracting the effects of histamine on a receptor site
medicinal drug: (medicine) something that treats or prevents or alleviates the symptoms of disease

Other hypernyms of antihistamine include medicament, medication, medicine.

antihistamine (noun)	medicinal drug (noun)
a medicine used to treat allergies and hypersensitive reactions and colds; works by counteracting the effects of histamine on a receptor site	(medicine) something that treats or prevents or alleviates the symptoms of disease