By Pat Anson, Editor

British researchers say a combination of two widely used drugs – an antidepressant and an opioid – can significantly relieve pain and other symptoms caused by neuropathy.

In a study published in the journal PAIN, researchers at Queens University say combining the painkiller morphine with the antidepressant nortriptyline relieved chronic neuropathic pain in nearly 90 percent of patients – significantly better than when either drug is used alone.

"Morphine and nortriptyline are excellent candidates for pain management because of the extensive research conducted on them, their low cost, and widespread availability all over the world," said Ian Gilron, MD, a professor in Queen's School of Medicine and anesthesiologist at Kingston General Hospital.

"Current neuropathic pain treatments are ineffective or intolerable for many sufferers so this new evidence supporting the morphine-nortriptyline combination is important news for patients."

Nortriptyline, an antidepressant sold under the brand names Aventyl and Pamelor, is already being used to treat pain in the arms and legs caused by multiple sclerosis. Morphine has long been used to treat both acute and chronic pain.

Neuropathic pain is characterized by tingling or burning sensations that develop as result of nerve damage caused by conditions such as shingles, diabetes, amputation, inflammation, and cancer. About 8% of adults worldwide suffer from neuropathy. Many drugs used to treat neuropathic pain, such as Neurontin and Lyrica, often don’t work or have unpleasant side effects.

In the double-blind, randomized study, 52 neuropathy patients were given a choice of trying every one of three treatments: morphine alone, nortriptyline alone, and a combination of the two drugs over six-week treatment periods. Patients were asked to record their pain levels and side effects during each treatment.

The average daily pain before treatment was 5.6, measured using a rating scale from 0-10. Average daily pain dropped to 2.6 when patients received the two drug combination. Patients taking nortriptyline and morphine alone rated their pain at 3.1 and 3.4, respectively.

Researchers said that common side effects for both drugs, which include constipation and dry mouth, did not worsen with the combined treatment.

"It's important to remember that we don't want to completely eliminate patients' ability to sense pain as it's a warning system for us, but we do want to find the right balance of pain relief and drug side effects," said Gilron

Nortriptyline and morphine are currently not available in a combined formulation. According to the Mayo Clinic, using the two drugs together is usually not recommended because they both cause sedation.