Chronic neuropathic pain: mechanisms and treatment.

There have been considerable advances in our understanding of the pathophysiology of neuropathic pain. There is still a lack of consensus about the optimal therapeutic strategy of such conditions, however. Drugs are generally selected on the basis of their established efficacy in randomized controlled studies in etiologically based groups of patients. These studies have been important in confirming the efficacy of antidepressants, antiepileptics, local anesthetics and derivatives, capsaicin, opioids, and N-methyl-D-aspartate antagonists in neuropathic pain, specifically painful diabetic neuropathy and postherpetic neuralgia. More specific therapeutic strategies based on precise quantified assessment of the various components of neuropathic pain are now increasingly used and may provide insight regarding the effects of treatments of particular symptoms (e.g., allodynia, hyperalgesia). In some cases, such assessment may also help to analyze the mechanisms involved in pain, thus allowing selection of treatment on a more rational basis. A mechanism-based approach seems promising for clinical research studies, although its application in current management remains challenging.