Percocet is pain killer used to treat moderate to severe acute (short-term) pain. The active ingredients of Percocet are oxycodone and acetaminophen. How should you take Percocet? Percocet may be taken with meals or with milk. If you miss a dose... If you take Percocet on a regular schedule, take it as soon as you remember. If it is almost time for the next dose, skip the one you missed and go back to your regular schedule. Never take 2 doses at once. Storage instructions... Store at room temperature. What side effects may occur? Side effects may include: dizziness, light-headedness, nausea, sedation, vomiting You may be able to alleviate some of these side effects by lying down.