This buy oxycodone online medication is used to relieve moderate to severe pain. belongs to a class of drugs known as opioid analgesics. It works in the brain to change the way your body feels and reacts to pain. belongs to a class of drugs known as opioid analgesics. It works in the brain to change how your body feels and responds to pain. The higher strengths of this drug (more than 40 milligrams per tablet) should be used only if you have been regularly taking moderate to large amounts of an opioid pain medication.