A drug used to treat Parkinson's Disease appears to reduce 'the inappropriately active' sensory nerve responses that cause fibromyalgia patients to feel pain.

The study participants were taking an average of more than two medications each, including narcotics, and most were disabled.

"This appears to be a novel medicine with remarkable safety that decreases fibromyalgia pain more effectively than any other single agent," said study co-author Dr. Andrew J. Holman, a rheumatologist at the University of Washington. The research appears in the August issue of Arthritis & Rheumatism.

Reliance on Medication

Fibromyalgia is a syndrome that strikes 3.7 million Americans over the age of 18, with women getting the disorder at a rate seven times that of men, according to the National Institutes of Health. The syndrome includes symptoms ranging from chronic and diffuse pain throughout the body to fatigue and depression. There is no cure for the ailment, and many sufferers take a variety of medications to treat their symptoms.

Because of this reliance on medication, Holman and his colleagues let participants remain on their other medicines throughout the 14-week trial, which they admitted was a limitation of the study.

Holman said, however, that by permitting people to take their regular medications, at doses they had maintained for at least six weeks before beginning the study, he was able to mimic real-life situations and reach patients who were seriously ill with fibromyalgia.

However, Florida rheumatologist Roland Staud said the overlap of medicines makes it hard to assess what caused the pain reduction.

"Does the drug affect the pain itself, or does it affect the effectiveness of the medicines they're already on?" he asked.

Reduces 'Inappropriate' Nerve Responses?

For the study, 57 women and three men were randomly selected to receive in a 2-to-1 ration of either pramipexole or a placebo for 14 weeks. The dosage was increased weekly, starting at .25 milligrams, until patients received the optimal dose of 4.5 milligrams for the last three weeks of the study. The graduated dose schedule avoided unnecessary side effects, Holman said.

At the end of the three and a half months, 49 people remained in the study. Of those, 42 percent of those who had taken pramipexole reported at least a 50 percent drop in pain, as did 14 percent of those who had taken the placebo.

Overall, 82 percent of the patients taking the drug noted some improvement in pain, compared to 57 percent of the placebo group. Side effects of the drug included weight loss and nausea, although the latter was reported by many in the placebo group as well.

Holman said that the drug, which stimulates dopamine production by binding to dopamine receptor sites in the brain, appears to reduce "the inappropriately active" sensory nerve responses that cause fibromyalgia patients to feel pain. In Parkinson's patients, the drug helps reduce tremors; it is also commonly used to treat restless leg syndrome.

"While this is an interesting study, it is very preliminary, and the results need to be replicated in other studies," Staud said.

More information: The National Library of Medicine has more on fibromyalgia.