Pharmacologic approaches to neuropathic pain

Injury to peripheral or central primary afferent neurons can produce severe and chronic neuropathic or deafferentation pain. This type of pain responds poorly, if at all, to nonsteroidal anti-inflammatory drugs and often is relatively opioid resistant. Several classes of drugs have been used with varying effectiveness to treat neuropathic pain. None are effective for all patients. Tricyclic antidepressants (TCAs) are often considered the drugs of choice at doses that are only one third to one half of the antidepressant doses. Available TCAs are contrasted by their side-effect profiles and pharmacokinetic characteristics. Amitryptyline is the most commonly used drug, but desipramine may be the TCA of choice for this indication. When the TCA alone is not sufficient an anticonvulsant can be added. Recent experience suggests that gabapentin may be the anticonvulsant of choice for this purpose. The used of systemic local anesthetics and topical capsaicin to deplete substance P is also described. Other classes of medications that have been used with varying results are discussed and include autonomic agents, depleting agents, andN-methyl-D-aspartate receptor antagonists. Methods of obtaining complete medication histories and of stopping ineffective drugs are described. The importance of an interdisciplinary, multimodel approach to the management of neuropathic pain is discussed.