Local analgesia with opioid drugs

These data suggest the presence of peripheral opioid receptors that are involved in the clinical perception of pain. This is a radical change in our traditional thinking of opioid pharmacology and pain management. Most clinicians have been taught that opioids work through the central nervous system. These new data depart from this traditionally held view of an exclusively central site of action. Further data, specifically, additional dose-response data with varying amounts of morphine, additional studies in pain syndromes other than knee arthroscopy, and the development and pharmacology of orally active opioid compounds that do not cross the central nervous system, are necessary to confirm and expand the present findings. The possibility of providing opioid pain relief free of central nervous system adverse effects is an exciting prospect. Additional studies of topical opioid preparations also would be of interest.