prescription drug vs medicament

prescription drug and medicament both are nouns.

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

As nouns, medicament is a hypernym of prescription drug; that is, medicament 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
medicament: (medicine) something that treats or prevents or alleviates the symptoms of disease

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

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