Antidepressants should be used as an initial treatment for the frequently disabling pain caused by nerve tissue damage, according to a new review of research on the issue.

Researchers reviewed 50 studies of 19 different antidepressants in the treatment of pain caused by nerve tissue damage, also known as neuropathic pain. They found that the older class of antidepressants called tricyclics can provide significant pain relief. These include medications such as amitriptyline, imipramine, clomipramine, desipramine, and nortriptyline.

Anticonvulsant drugs were also shown to alleviate neuropathic pain.

Nerve pain from diabetes, called diabetic neuropathy, occurs after chronically elevated blood sugars damage nerves throughout the body. A complication of shingles called postherpetic neuralgia causes nerve pain for weeks to years after the shingles rash has disappeared. And some cancer treatments -- radiation and some chemotherapy drugs -- can also result in nerve damage.

There is limited evidence that newer antidepressants, called selective serotonin reuptake inhibitors (SSRIs), may also provide neuropathic pain relief. Researchers say more studies are needed before they can be recommended for this use. SSRIs include Prozac, Celexa, Luvox, Zoloft, and Paxil.

Pain caused by nerve tissue damage often occurs as a burning, tingling, or stabbing sensation.

Researchers say antidepressants have been used for neuropathic pain for many years, and this review of research shows that it is still probably the best approach to take. Antidepressants are thought to ease pain caused by nerve damage by dampening pain signals sent to the brain.

Anticonvulsant drugs, such as Neurontin, Tegretol, and Dilatin, originally developed to treat epilepsy, are also often used to treat nerve pain, but researchers say they should be reserved as a second line of treatment. It remains unclear how these drugs work to dampen nerve pain.

Read WebMD's "Get the Facts about Diabetes-Related Nerve Problems"

Older Antidepressants Still Work for Nerve Pain

In the review, which appears in the current issue of the Cochrane Library, researchers evaluated studies on antidepressants and anticonvulsant drugs in the treatment of neuropathic pain involving more than 2,500 people.

The results showed that two-thirds of people with pain caused by nerve damage who took tricyclic antidepressants obtained at least moderate pain relief. But about one-fifth found the side effects of antidepressant treatment, such as drowsiness, dry mouth, and blurred vision, unacceptable and stopped taking the drugs.

The study showed that tricyclic antidepressants, particularly Amitril, were most effective in easing neuropathic pain caused by diabetes and shingles.

Although these results are promising, researchers say antidepressants do not cure or eliminate all pain.

"The amount of pain reduction is moderate at best. Typically the pain reduction averages around 40 percent in 50 percent of treated patients," says researcher Dennis C. Turk, PhD, of the University of Washington, in a news release. "This means that a significant proportion of patients do not obtain even moderate reductions in pain, and even those who do continue to experience significant pain."

Researchers say more studies are needed to evaluate the effects of newer antidepressants as well as alternative medicines, such as St. John's wort, before they can be recommended for treating neuropathic pain.

Read WebMD's "Learn More About Diabetes Complications"

Anticonvulsants May Also Help Nerve Pain

Researchers say the results of their review of anticonvulsants in treating neuropathic pain are both encouraging and conflicting.

Anticonvulsants were originally developed to treat epilepsy in the 1960s and have increasingly been used to treat pain. The drugs are thought to work by quieting abnormal firings of the nerves in the brain and central nervous system.

In their review, researchers analyzed 23 trials of anticonvulsant drugs involving more than 1,000 people.

They say the results of these studies are conflicting and suggest that each anticonvulsant drug needed to be evaluated independently to determine its effectiveness in treating neuropathic pain in comparison with other anticonvulsants and antidepressants.

For example, 15 studies of Neurontin showed that its effectiveness was comparable to another anticonvulsant, Tegretol, in relieving neuropathic pain. Neurontin has fewer side effects, but researchers say it is more expensive than other alternatives and cheaper treatments are also effective.

Therefore, researchers say anticonvulsants should be reserved as a second choice for treating pain caused by nerve tissue damage after first trying treatment with antidepressants.

By Jennifer Warner, reviewed by Brunilda Nazario, MD

SOURCES: Saarto, T. The Cochrane Database of Systemic Reviews, July 20, 2005. News release, Health Behavior News Service.