Buy Oxycodone 5 mg Online Rx Prescription is a painkiller that reduces the intensity of pain and blocks the substance in the brain that causes it. According to World Health Organization, the drug is a useful tool for the treatment of moderate to severe pain. Oxycodone is a powerful, long-acting opioid pain reliever used as an analgesic (painkiller). It is one of three drugs in the family of opioid agonists used to relieve pain and reduce coughs.