Clinical meaning
Opioid analgesics act on mu, kappa, and delta receptors in the central nervous system and peripheral tissues to modulate pain perception and emotional response to pain. Mu receptor activation provides analgesia, euphoria, and respiratory depression. Opioids reduce the perception of pain at the level of the spinal cord (ascending pathways) and activate descending inhibitory pathways. The most dangerous adverse effect is respiratory depression, which occurs through direct suppression of the medullary respiratory center. The nurse monitors pain levels, vital signs (especially respiratory rate and oxygen saturation), level of consciousness, and reports concerns to the RN.