Lack of pre-emptive analgesic effects of local anaesthetics on neuropathicpain

We investigated the significance of pre-emptive analgesia using a well-know n model of neuropathic pain in rats. Lignocaine, bupivacaine or saline was applied locally to the left L5-L6 spinal nerve before or 4 days after nerve injury. Mechanical allodynia was then evaluated before and after injury. P re- and post-injury treatment with local anaesthetics both resulted in a tw o- to threefold increase in the pain threshold, as manifested by a signific ant increase in von Frey measurements. However, this effect lasted only 24 h. Our study in rats questions the beneficial effect of a single dose of lo cal anaesthetic as pre-emptive analgesia.