Naltrexone appears to relieve fibromyalgia pain

Apr 20 2009

For Tara Campbell, the onset of her fibromyalgia began slowly with repeated sore throats, fevers and fatigue.

By the time she was diagnosed, a year later, she had become so debilitated by flulike symptoms and exhaustion that she often couldn't get off the couch all day.

"Fall, a year ago, I hit my very, very worst," said Campbell, 39, of Walnut Creek, Calif. "I felt overall pain to the point that even when my children or husband just touched me it hurt."

Campbell's symptoms still linger, but since taking part in a Stanford University School of Medicine clinical trial in the spring of 2008, she's improved enough that she's gone back to working again as an interior decorator and even headed up the fundraising auction at her daughters' school.

"I am really, really good," Campbell said. "Having said that, I'm still not 100 percent. I'm still not that person I was before."

Campbell was one of 10 women with fibromyalgia to take part in a small pilot study at Stanford over a 14-week period to test the new use of a low dose of a drug called naltrexone for the treatment of chronic pain. The drug, which has been used clinically for more than 30 years to treat opioid addiction, was found to reduce symptoms of pain and fatigue an average of 30 percent over placebo, according to the results of the study to be published April 17, 2009 online in the journal Pain Medicine .

"Patients' reactions were really quite profound," said senior author Sean Mackey, MD, PhD, associate professor of anesthesia and chief of the pain management division at Stanford University Medical Center. "Some people decided to come off other medications. Some people went back to work really improving their quality of life."

Still, Mackey and his colleagues remain cautious about recommending the drug this early on in the research process. "People need to understand that while we're excited about preliminary results, they are still preliminary, and we need to do longer studies with more patients. There is still a significant amount of work to be done." The researchers are moving ahead with a second, longer-term trial of 30 patients who will be tested during a 16-week period.

The drug is particularly promising, the study states, because of the few treatment options available for fibromyalgia patients, its low cost of about $40 a month and its limited side effects. Vivid dreams were reported by a few participants.

Still considered a controversial diagnosis, fibromyalgia is a disorder classified by chronic widespread pain, debilitating fatigue, sleep disturbance and joint disorder. Advocates and doctors who treat the disorder, estimate it affects as much as 4 percent of the population. "The symptoms of fibromyalgia are commonly seen in a number of other diseases, and there is no well-established and objective blood test to confirm the diagnosis," said Jarred Younger, PhD, the study's lead author and an instructor in anesthesia and pain management at Stanford. "In the meantime, new treatments that work particularly well for fibromyalgia go a long way toward validating the usefulness of the diagnosis."

The idea to explore the use of a low-dose of naltrexone as a treatment for fibromyalgia began about two years ago when Younger began searching for relief for patients with the disorder. "I was asking patients, 'Does anything work for you?'" he recalled. "A lot of people in support groups were saying, 'Yeah, I tried naltrexone and it works for me.' It just kept coming up."

The use of naltrexone to treat pain at first seems counterintuitive, Younger said, because at normal doses the drug actually blocks the body's pain relief systems. However, naltrexone appears to have the opposite effect when given at a lower dose. Naltrexone, at these lower doses, is thought to work by modulating glial cells in the nervous system, Mackey said. Glial cells provide support and protection for neurons and act as a link between the neuronal and inflammatory systems.

"We're learning more and more that maybe by modulating these glial cells we can impact the abnormal processing of pain in these patients," Mackey said.

During the study, the women used a handheld electronic device to capture their symptoms on a daily basis. They took a placebo for two weeks and then the drug for eight weeks, but they weren't told when they were taking the drug or the placebo.

Some of the women, including Campbell, have continued to take the drug after the end of the study because the results were so positive, Younger said.

"Even after the study, it just got better and better and better," Campbell said. "I think my improvement was about 40 percent during the study. When you're not capable of doing much of anything, that's a lot. I still have localized pain, but I don't have the overall body pain. I can live with that if I don't have the fatigue and flulike symptoms. I'm much more back to normal."