THURSDAY, Sept. 9 (HealthDayNews) -- A new antidepressant called duloxetine improved symptoms of fibromyalgia -- a chronic and painful musculoskeletal disorder -- in women but not in men, researchers report.
Duloxetine (brand name Cymbalta) was recently approved by the U.S. Food and Drug Administration to treat major depression and nerve pain suffered by those with diabetes. In the new study, published in the September issue of Arthritis & Rheumatism, the drug was used "off-label," which is legal.
"Antidepressants have been used to treat fibromyalgia for over 10 years," said study author Dr. Lesley Arnold, an associate professor of psychiatry at the University of Cincinnati College of Medicine. "The problem has been those medications are poorly tolerated," she said, adding that side effects include weight gain, potential heart problems and excess sedation.
"We have been looking for alternatives," Arnold said.
Fibromyalgia is marked by body pain and muscle tenderness at several body sites, and there also can be headaches, sleep disturbances and fatigue. An estimated 3 percent to 6 percent of the U.S. population has the disorder and it's far more common in women than in men, according to the National Fibromyalgia Association.
The cause is not known, but the disorder has been linked to abnormalities in the brain neurotransmitters serotonin and norepinephrine. Both are linked to mood and recognized for their role in depression. According to the study authors, there is no FDA-approved treatment for fibromyalgia.
Duloxetine works differently than some other antidepressants, affecting levels of both serotonin and norepinephrine rather than just serotonin, Arnold said. The drug produces the benefits of the other antidepressants without the downsides, according to Arnold, whose colleagues on the study included researchers from Eli Lilly and Co., the drug's manufacturer.
In the study, Arnold and her team evaluated 207 patients, mostly women, with fibromyalgia. About a third had also been diagnosed with depression. The subjects were randomly assigned to a placebo group or to a treatment group, which received 60 milligrams of duloxetine twice a day for 12 weeks.
Then they were evaluated using the Fibromyalgia Impact Questionnaire, commonly used to determine the effect of a treatment. It asks about the ability to perform common activities such as going to work, shopping, doing laundry, preparing meals, driving a car and climbing stairs.
Thirty percent of the women in the duloxetine group had a 50 percent or greater improvement in their pain, Arnold said, compared with just 16.5 percent in the placebo group. And, she said, the improvement in pain reduction seemed to be independent of the effect on mood.
Those who received duloxetine demonstrated greater improvement on most of the measures evaluated on the questionnaire, she said.
Why the treatment didn't work for the men isn't clear, Arnold said, but the answer could lie with the small sample size. Only 23 men were included in the study.
Dr. Daniel J. Clauw, a professor of medicine at the University of Michigan and an expert on fibromyalgia, called the new research "a well-done study."
But he noted there was more improvement with daily activities than pain management. He couldn't predict whether more doctors treating patients with fibromyalgia would be likely to use the new antidepressant off-label.
But the outlook is getting brighter for those with the condition, Clauw said. "Nearly every large pharmaceutical company is testing one or more compounds for fibromylagia," he said.
To learn more about fibromyalgia, visit the National Fibromyalgia Association.