prescription vs nonprescription

prescription is a noun but nonprescription is not a noun.

Word	Noun	Adjective	Verb	Adverb
prescription	Yes	Yes	No	No
nonprescription	No	Yes	No	No

prescription (noun)	nonprescription (noun)
a drug that is available only with written instructions from a doctor or dentist to a pharmacist
directions prescribed beforehand; the action of prescribing authoritative rules or directions
written instructions from a physician or dentist to a druggist concerning the form and dosage of a drug to be issued to a given patient
written instructions for an optician on the lenses for a given person

prescription (adjective)	nonprescription (adjective)
available only with a doctor's written prescription	purchasable without a doctor's prescription