nonprescription vs over-the-counter

nonprescription and over-the-counter both are adjectives.

Word	Noun	Adjective	Verb	Adverb
nonprescription	No	Yes	No	No
over-the-counter	No	Yes	No	No

As adjectives, nonprescription and over-the-counter are synonyms defined as:

nonprescription and over-the-counter: purchasable without a doctor's prescription

nonprescription (adjective)	over-the-counter (adjective)
purchasable without a doctor's prescription	purchasable without a doctor's prescription
	(of securities) not traded on a stock exchange