Neuropathic pain syndromes. (Pain).

A growing understanding of shared mechanisms has led to more tailored pain therapy using drugs originally for depression or seizures, Dr. Bennet E. Davis explained at a psychopharmacology conference sponsored by the University of Arizona.

Neuropathic pain responds to drugs that produce a blockade of neuronal sodium channels, inhibiting nerve terminal release of dopamine, [gamma]-aminobutyric acid, and glutamate.

Tricyclic antidepressants are an example of this type of drug, as are anticonvulsants. But selective serotonin reuptake inhibitors are not, which explains why they are less effective than tricyclic antidepressants in blocking neuropathic pain, said Dr. Davis of the university's Pain Institute in Tucson.

Symptom-based drug choices are the result of both trial and error, as well as small amounts of data for support.

His first line for treating constant neuropathic pain is a tricyclic antidepressant or venlafaxine, followed by an anticonvulsant drug or bupropion. For lancinating pain, which is best relieved by sodium channel blockers, oxcarbazepine or lamotrigine is a first choice, carbamazepine a second choice. According to animal studies, lamotrigine is more effective than carbamazepine for treating pain, he noted.

In general, Dr. Davis starts with gabapentin or venlafaxine to treat patients with allodynia. If these do not work or ...