Sept. 30 (HealthDay News) -- People with nerve pain respond better to a combination treatment using the anticonvulsant gabapentin and antidepressant nortriptyline than to treatment with either drug alone, according to Canadian researchers.

The study findings suggest that combination treatment could be used to help people who only partially respond to one drug or the other.

Nerve, or neuropathic, pain -- which affects 2 to 3 percent of the population -- is "initiated or caused by a primary lesion or dysfunction in the nervous system," according to a news release from The Lancet, which is publishing the study online Sept. 29. Conditions that cause neuropathic pain include nerve problems in the spine, diabetes-related nerve damage and postherpetic neuralgia (PHN), which is nerve pain caused by the varicella zoster virus that can follow an outbreak of shingles.

The study included 56 people with PHN or diabetic nerve disease who had a daily pain score of at least 4 on a scale of 0 to 10. They were randomly selected to be given gabapentin alone, nortriptyline alone, or both drugs. Everyone received each type of treatment, with each treatment period lasting six weeks.

At the start of the study, the average daily pain level among the participants was 5.4. At maximum tolerated doses, average daily pain levels were 3.2 while people were taking gabapentin, 2.9 for while taking nortriptyline and 2.3 while taking the combination treatment, the researchers reported.

"This trial shows that combination of an antidepressant and an anticonvulsant drug seems to be superior to monotherapy for neuropathic pain," wrote study author Ian Gilron, director of clinical pain research at Queen's University and Kingston General Hospital in Ontario, and colleagues.

"Although development of more effective and better-tolerated monotherapies is much anticipated, our findings suggest that drug combinations represent the most effective strategy for many patients with neuropathic pain," the researchers concluded. "On the basis of our results, we recommend combined gabapentin and nortriptyline for patients who have a partial response to either drug alone and seek additional pain relief."

SOURCE: The Lancet, news release, Sept. 29, 2009