opioid opioid opioids are substances that act on opioid receptors to produce morphine-like effects. medically they are primarily used for pain relief, including anesthesia. other medical uses include suppression of diarrhea, replacement therapy for opioid use disorder, reversing opioid overdose, and suppressing cough. extremely potent opioids such as carfentanil are approved only for veterinary use. opioids are also frequently used non-medically for their euphoric effects or to prevent withdrawal. opioids can cause death and have been used for executions in the united states. opioiddrug classchemical structure of morphine, the prototypical opioid.class identifiersusepain reliefatc coden02amode of actionopioid receptor