Emerging pharmacologic mechanisms of buprenorphine to explain experience of analgesia versus adverse effects

Buprenorphine's unique pharmacologic mechanisms of action lend itself to a higher level of complexity than its typical characterization as a partial agonist at µ-opioid receptors. It is well-documented that its additional activity at Δ- and κ-opioid receptors, and opioid receptor ligand 1 may be associated with varying degrees of analgesia and usual opioid-related adverse effects. However, novel downstream molecular and cellular mechanisms from µ-opioid receptor activation contain potential new insights into its overall unique effects. These include buprenorphine's peculiar ability to induce analgesia at escalating doses, while exhibiting a plateaued effect on respiratory depression, euphoria, gastrointestinal (GI) motility, depression, anxiety, and addictive potential. Thus, this review aims to discuss several of these emerging mechanisms to gain a better understanding of these curious actions, as well as support much of this in vitro evidence with various human clinical trial data to further support buprenorphine's place on the analgesic ladder.