<Tr> <Th> MeSH </Th> <Td> D000701 </Td> </Tr> <Tr> <Td_colspan="2"> In Wikidata </Td> </Tr> <P> 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, treating opioid use disorder, reversing opioid overdose, suppressing cough, and suppressing opioid induced constipation . Extremely potent opioids such as carfentanil are only approved for veterinary use . Opioids are also frequently used non-medically for their euphoric effects or to prevent withdrawal . </P> <P> Side effects of opioids may include itchiness, sedation, nausea, respiratory depression, constipation, and euphoria . Tolerance and dependence will develop with continuous use, requiring increasing doses and leading to a withdrawal syndrome upon abrupt discontinuation . The euphoria attracts recreational use, and frequent, escalating recreational use of opioids typically results in addiction . An overdose or concurrent use with other depressant drugs commonly results in death from respiratory depression . </P>

The analgesic effect of opioids is due to their