A medication used to treat Parkinson’s disease is showing promise in treating people with restless legs syndrome, according to a new study.

Restless legs syndrome can be extremely disruptive, especially when it comes to sleep. Patients have an irresistible urge to move their legs and may feel crawling, tingling, pulling, or painful sensations in their legs. Though the cause of restless legs syndrome is unknown, studies have suggested that the condition results from abnormalities in the brain chemical known as dopamine.

A study in the journal Movement Disorders shows the Parkinson’s drug Requip, which works like dopamine, relieves symptoms of restless legs syndrome, improving sleep and quality of life for people with the condition.

Still, it doesn’t cure the problem, which affects one in 10 people to varying degrees.

The FDA is reviewing Requip as a treatment for restless legs syndrome. Made by WebMD sponsor GlaxoSmithKline, the drug directly stimulates nerve cells in the brain that aren’t being stimulated by dopamine. A similar drug called Mirapex has also shown promise in small clinical trials.

Requip and Mirapex are prescribed to help control the tremors and shaking seen with Parkinson’s disease. Other drugs that affect dopamine have also been tried for restless legs syndrome, but some may cause scarring of heart valves.

Requip was tested against a placebo pill in more than 260 restless legs patients in North America, Europe, and Australia. Researchers included Arthur Walters, MD, of the New Jersey Neuroscience Institute at JFK Medical Center.

Participants were split into two groups. One group took Requip one to three hours before bedtime every day for 12 weeks, starting at 0.25 mg per day and increasing as necessary to a maximum dose of 4 mg daily.

The other participants took a placebo. No one knew whether they were taking the drug or the placebo.

There is no lab test for restless legs syndrome, so participants’ reports were important. They rated any changes in their symptoms, as well as their sleep and quality of life.

By the study’s end, 60 percent of the Requip group said their symptoms were “much” or “very much” improved, compared with 40 percent of the placebo group. Some improvements were seen within a week and lasted throughout the study.

Patients taking Requip also said they slept better at night and felt less drowsy during the day. Compared with the placebo group, they reported feeling more energetic, sociable, and less tired.

The drug was well tolerated, say the researchers. Most side effects were mild or moderate and included nausea, headache, fatigue, dizziness, upper respiratory tract infection, and vomiting. Less than 10 percent of participants in each group quit the study because of side effects.

The study was conducted in 2002. Requip also showed promise in a similar restless legs study conducted in Europe and reported in January 2004.