What is Oxycontin? OxyContin (oxycodone) is an opioid pain reliever that is also known as a narcotic. It is a prescription medicine that helps treat moderate to severe pain. Oxycodone is an opioid analgesic that works by changing the way your body perceives and responds to pain. You can buy OxyContin online. Important Information Do not use OxyContin if you have severe asthma or breathing problems or a blockage in your stomach or intestines.