A narcotic used as a pain medication. It appears to be an agonist at KAPPA RECEPTORS and an antagonist or partial agonist at MU RECEPTORS.

A synthetic mixed opioid agonist-antagonist with analgesic properties. Although its exact mechanism has not been fully delineated, it is hypothesized that upon administration, nalbuphine binds to kappa receptors in the central nervous system (CNS), thereby inhibiting the release of neurotransmitters that mediate pain, such as substance P. Additionally, nalbuphine exerts post-synaptic inhibitory effects on interneurons and output neurons of the spinothalamic tract, responsible for transporting nociceptive information. Compared to other opioid agents that stimulate mu receptors, nalbuphine antagonizes mu receptors, thereby potentially producing less intense respiratory depression.