Drug combo packs more relief for chronic nerve pain, scientists say

By ANDRÉ PICARD

Friday, April 1, 2005 Updated at 7:58 AM EST

From Friday's Globe and Mail

Canadian scientists have found a new formula for treating the chronic, debilitating pain that results from nerve damage.Researchers at Queen's University in Kingston, Ont., found that combining morphine with an anti-seizure drug provides better pain relief than existing treatments.

"We now have the first clinical evidence that combining these drugs provides better pain relief, with comparable side effects," said Dr. Ian Gilron, director of clinical pain research in the Departments of Anesthesiology and Pharmacology & Toxicology.

"This new treatment approach has the potential to dramatically improve quality of life for people suffering from neuropathic pain."

Neuropathic pain is a condition that has long puzzled researchers because it is often experienced in areas of the body that appear uninjured.

In the study, which in published in yesterday's edition of the New England Journal of Medicine, researchers treated patients with morphine, the anti-seizure drug gabapentin, a combination of the two drugs, and with a placebo or sugar pill.

All 57 patients received, in turn, all four treatments.

The combination of morphine and gabapentin worked best, and worked at a lower dose than any of the drugs taken individually, researchers reported.

Isabel Abbott of Beeton, Ont., suffers from postherpetic neuralgia, a form of nerve damage caused by shingles, and has been living in chronic pain for four years.

"It hurts all the time," she said. "It's like an electric shock going through my leg, and it can happen any time, anywhere." The shooting pains occur on the left side of her body, anywhere from her shoulder to her knee.

Ms. Abbott, who took part in the study, said her pain levels fell dramatically with the combination treatment.

"It's an immense relief to have found a medication," she said.

The study focused on people suffering from two specific forms of nerve-related pain:

postherpetic neuralgia, which occurs in about 20 per cent of people who have shingles (a reactivation of the virus that causes chickenpox);

and diabetic neuropathy, a condition in which diabetics suffer from a constant burning pain in the soles of their feet and shooting pains in the lower leg.

Existing treatments have a number of side effects, including constipation, dry mouth and a profound lethargy that comes from being sedated.

The combination treatment has those same side effects, but to a lesser extent because the dosage is lower.

Dr. Gilron said while only two conditions were studied, the findings could benefit patients with a number of types of chronic pain, such as that experienced by cancer sufferers, those with spinal injuries, and the pain caused by chemotherapy and mastectomy surgery.

"The numbers of people affected are staggering, and the impact of the problem is devastating and costly," he said.

The new research was funded by the Canadian Institutes of Health Research.

Updated 4-5-05