prescription drug vs medication

prescription drug and medication both are nouns.

Word	Noun	Adjective	Verb	Adverb
prescription drug	Yes	No	No	No
medication	Yes	No	No	No

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

prescription drug: a drug that is available only with written instructions from a doctor or dentist to a pharmacist
medication: (medicine) something that treats or prevents or alleviates the symptoms of disease

Other hypernyms of prescription drug include medicament, medicinal drug, medicine.

prescription drug (noun)	medication (noun)
a drug that is available only with written instructions from a doctor or dentist to a pharmacist	the act of treating with medicines or remedies
	(medicine) something that treats or prevents or alleviates the symptoms of disease