Oxycontin is a long-acting form of morphine that's used to treat moderate or severe pain. It's also sometimes used for end-of-life care or palliative care. Oxycontin is a long-acting narcotic pain reliever. It works by attaching to opioid receptors in your brain and nervous system, blocking them from transmitting pain signals. Oxycontin is a prescription painkiller. It works by reducing the sensation of pain in your body, helping you to stay comfortable and live your life.