https://medixway.com/pain-relief/oxycodone/Oxycodone is an opioid painkiller. It's used to treat severe pain, for example after an operation or a serious injury, or pain from cancer.Oxycodone is only available on prescription. It comes as slow-release tablets, standard tablets and capsules, and a liquid that you swallow. It can also be given by injection, but this is usually done in hospital.