Oxycodone is a semi-synthetic opioid analgesic. It works by binding to mu-opioid receptors in the central nervous system, altering pain perception and emotional response to pain. It is highly effective—and highly addictive. Oxycodone is a semi-synthetic opioid analgesic. It works by binding to mu-opioid receptors in the central nervous system, altering pain perception and emotional response to pain. It is highly effective—and highly addictive.