Peripheral opioid analgesia.

Major recent findings in peripheral opioid analgesia include the relative lack of tolerance under inflammatory conditions, tetrapeptides as novel peripherally restricted compounds, the potent anti-inflammatory activity of mu and kappa agonists and the identification of selectins as important molecules governing the homing of opioid cells to injured tissue. Clinical studies have now moved into the field of chronic arthritic pain, a problem of major relevance and prevalence.