Some patients with severe fibromyalgia, a chronic pain disorder, respond to a drug usually used to treat Parkinson’s disease with a significant improvement in their symptoms, researchers report.

The drug is pramipexole, marketed as Mirapex, which stimulates dopamine receptors in the brain. “I suspect that this class of medication will transform the treatment of fibromyalgia,” said Dr. Andrew J. Holman from Pacific Rheumatology Associates, Renton, Washington.

Fibromyalgia is a chronic condition marked by widespread muscular and joint pain, as well as specific “tender” points that typically occur in the neck, spine, hips and shoulders. Other symptoms include sleep disturbances and fatigue, Depression and Irritable bowel syndrome.

Holman and Robin R. Myers investigated the effects of pramipexole in a 14-week clinical trial involving 40 patients with fibromyalgia, mostly white women. Half the participants were on narcotics for pain, and a third were disabled by their condition.

Compared with individuals assigned to get an inactive “placebo”, those given pramipexole experienced significant reductions in pain, the researchers report in the medical journal Arthritis & Rheumatism. Specifically, 42 percent of the pramipexole group had at least a 50 percent reduction in pain, compared with 14 percent of the placebo group.

“This is the highest response rate yet reported for a single medication to treat fibromyalgia,” Holman said. He cited response rates ranging from 29 percent to 36 percent with other drugs in prior studies.

Pramipexole-treated patients also experienced improvements in standardized fibromyalgia scores, and in measures of pain, fatigue, and function, the report indicates.

Side effects included weight loss and increased anxiety in the pramipexole group and weight gain in the placebo group, the researchers note.

“The most important message here is that even severe fibromyalgia is treatable,” Holman concluded.

“As with most complex disorders, we should not expect simple answers quite yet,” he cautioned. “Doses of effective medications have to be carefully adjusted to get maximum results in other disorders, and fibromyalgia is similar.”

SOURCE: Arthritis & Rheumatism, August 2005.