Which of the following is classified as a mixed function opioid?

Buprenorphine is classified as a mixed-function opioid because it partially activates the mu-opioid receptors while also exhibiting antagonist properties at the kappa-opioid receptors. This unique dual action makes it different from full agonists, as it produces analgesic effects but does not provide the same level of euphoria or respiratory depression typically associated with full agonists like oxycodone, fentanyl, and hydromorphone.

Additionally, the partial agonist nature of buprenorphine allows it to function as a safer alternative in pain management and substance use disorder treatment, as it has a "ceiling effect," which reduces the risk of overdose compared to full agonists. This balance of efficacy and safety is a distinguishing characteristic of mixed-function opioids, effectively addressing pain without the increased risk of adverse effects common with full opioid agonists.