[Mechanism of action and clinical use of opioids administered by the peripheral perineural route]

Experimental studies have shown that opioids could produce two types of effect on neuronal excitability. The first one, aspecific, is a local anesthetic action on the nerve fiber with a diminution of sodium and potassium conductance. The second is specific: the sodium conductance lowering is due to a linkage of the opioid with a receptor on the internal face of the membrane. Opioids could also migrate to the posterior horn of the spinal cord after linkage with axonal receptors. Clinical studies have proved that opioid injection in peripheral nervous trunks and specially in the brachial plexus produce a prolonged analgesia status in the post operative period but also and mostly in the chronic pain. The more liposoluble opioids like fentanyl and buprenorphine are the more effective.