New treatment for fibromyalgia

Study demonstrates effectiveness of the antidepressant duloxetine for improving symptoms and relieving pain

Fibromyalgia is a chronic, incapacitating musculoskeletal disorder. Nearly six times more common in women than in men, fibromyalgia is marked by widespread body pain and muscle tenderness, often accompanied by headaches, sleep disturbances, and fatigue. While its cause remains a mystery, fibromyalgia has been linked to abnormalities in the brain’s neurotransmitters, serotonin and norepinephrine–chemicals key to mood and widely recognized for their role in depression. Not all patients with fibromyalgia, however, have depression or respond to antidepressants. Treatment studies of the other types of antidepressant drugs, including selective serotonin uptake inhibitors and tricyclic agents, have had mixed results.

A new and different antidepressant, duloxetine, works by inhibiting the reuptake of both serotonin and norepinephrine. In a recent clinical trial conducted for the treatment of fibromyalgia–one of the largest ever–duloxetine was shown to reduce pain and improve a range of disease symptoms, significantly and safely. The results, published in the September 2004 issue of Arthritis & Rheumatism, offer the promise of relief for women with fibromyalgia.

“Our results suggest that duloxetine improves pain and tenderness, the hallmark characteristics of fibromyalgia,” states Lesley M. Arnold, M.D., who coordinated the research at 18 centers, including the University of Cincinnati College of Medicine, Indiana University Medical School, and Harvard Medical School. “The effect of duloxetine on the reduction of pain,” Dr. Arnold further notes, “appears to be independent of its effect on mood.”

To test duloxetine’s effectiveness on the range of symptoms, researchers recruited 207 patients, all meeting the American College of Rheumatology criteria for fibromyalgia. Like the majority of those with this disease, the majority of the participants–89 percent–were women. 87 percent of the subjects were Caucasian and the mean age was 49. Just over a third of the patients–38 percent–had been diagnosed with depression. On a random basis, the patients were prescribed one of two treatments for a course of 12 weeks. About half, 104 individuals, received 60 milligrams of duloxetine twice a day. The remaining 103 patients were given a placebo. Both groups were evaluated and scored, using the Fibromyalgia Impact Questionnaire and other standard measures, for improvements in their condition.

In various measures of disease–from pervasive pain to tiredness to tenderness–the female fibromyalgia patients treated with duloxetine improved significantly over those treated with a placebo. One of the most dramatic changes was in the reduction of the number of tender points–places on the body where it hurts to touch–and the increase of pressure pain threshold. Women with or without depression receiving duloxetine benefited emotionally and physically, reporting improvements in general mood, ability to function, and overall enjoyment of life.

For the study’s 23 men, however, duloxetine did little to change their condition. Although researchers reported some evidence of improvement in tender point measures among duloxetine-treated men over their placebo-treated counterparts, it was not statistically significant. “The reasons for the sex differences in response are unclear,” Dr. Arnold observes. “Because the male subgroup was small, reflecting the much higher prevalence of fibromyalgia in women, the results of the study may not be generalizable to all men with fibromyalgia. There may also be sex differences in fibromyalgia that affect treatment response.”

As Dr. Arnold notes, further research is needed on larger samples of not only men but also other groups with fibromyalgia to evaluate duloxetine’s effectiveness.