People who suffer from debilitating neuropathic pain may get more relief and sleep better by combining two commonly-prescribed drugs.
A new, federally-funded study by Queen's University researchers has found that taking the drugs together is a more effective treatment than taking either of them individually.
When given both an anti-seizure drug (gabapentin) and an antidepressant (nortriptyline), patients suffering from neuropathic pain caused by nerve damage or disease experienced less pain than when they took one or the other individually, reports Ian Gilron, director of Clinical Pain Research for Queen's Departments of Anesthesiology, and Pharmacology & Toxicology, and an anesthesiologist at Kingston General Hospital.
"It was also exciting to discover the effect of this combination on sleep interference," adds Dr. Gilron, noting that people rated sleep interference with the combined drugs as 1.0 on a scale of 10, compared to 2.2 when they took each drug individually. "That's a very important issue for this group of patients, whose debilitating, unrelenting pain often interferes with normal sleep."
This is the first time Dr. Gilron has been able to find a drug combination that also helps patients sleep better. An earlier trial investigated the effects of combining morphine - the other type of commonly prescribed drug for neuropathic pain - with the anti-seizure drug gabapentin. The patients' pain lessened significantly, but they still had as much trouble sleeping.
Dr. Gilron says it's important to understand how drugs interact, since 45 per cent of Canadians being treated for neuropathic pain take two or more pain drugs. There may also be safety issues. "We need more evidence from carefully conducted trials in support of each particular combination, and let the doctors and patients know about such results," Dr. Gilron stresses.
While this research focuses on two specific types of neuropathic pain - diabetic neuropathy and postherpetic neuralgia - the methodology could also be applied to the study of other chronic conditions such as cancer-related pain, spinal disk disease, and the pain experienced after chemotherapy and mastectomies, says Dr. Gilron.
Results of the study, funded by the Canadian Institutes of Health Research (CIHR), are published in the international health journal The Lancet.
"This is a very interesting and important result," says Dr. Jane Aubin, Scientific Director of CIHR's Institute of Musculoskeletal Health and Arthritis. "Many chronic pain sufferers don't sleep well, and they get caught in a vicious cycle in which less sleep equals more pain. Dr. Gilron's work offers new hope to Canadians desperate to put an end to this debilitating situation."
Also on the Queen's team are researchers Joan Bailey (Anesthesiology), Dongsheng Tu (Mathematics and Statistics), Ronald Holden (Psychology,) Robyn Houlden (Medicine); and Alan Jackson from the University of Manitoba.
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