Pramipexole (Mirapex), which is commonly used to treat this neurological disease, makes many people worse, said lead researcher Richard Allen, an associate professor of neurology at Johns Hopkins University School of Medicine in Baltimore.
Lyrica works just as well and doesn't worsen the condition, Allen said.
People with restless legs syndrome -- now also known as Willis-Ekbom disease -- feel throbbing, creeping or other unpleasant sensations in the legs and an uncontrollable urge to move them.
Symptoms occur primarily at night, and most people with restless legs syndrome have trouble falling asleep and staying asleep. Moving the legs relieves the discomfort; remaining in a resting position often activates symptoms. Untreated, the condition results in exhaustion and daytime fatigue, experts say.
"When the disease becomes worse it can become really bad," Allen said. Besides disturbing sleep, it affects patients 24 hours a day, he noted.
The report, published Feb. 13 in the New England Journal of Medicine, was funded by Pfizer, the maker of Lyrica.
"Long-term management of restless legs syndrome affecting sleep and quality of life remains problematic," said Dr. Sudhansu Chokroverty, from the New Jersey Neuroscience Institute at JFK Medical Center in Edison. Chokroverty wrote an accompanying journal editorial.
The most commonly used medications, called "dopamine agonists," are associated with worsening of the disease in a large number of patients, he said.
This multicenter study was launched in an attempt to resolve "the vexing problem of long-term issues in restless legs syndrome," Chokroverty said.
Although Allen thinks Lyrica should be seen as a viable treatment for restless legs syndrome based on the current findings, Chokroverty said further studies are still needed. Whether Lyrica's positive effects will be sustained without undesirable side effects and whether the treatment will improve quality of life, including sleep, are among the questions that need to be addressed, he said.
"Many gaps remain in our knowledge about treatment of restless legs syndrome," Chokroverty said. "Hopefully, this recent progress in research will encourage researchers to develop an ideal drug for this common but uncommonly diagnosed condition."
Allen noted that Lyrica is expensive, running to more than $250 for 60 capsules. But there are less expensive alternatives, such as generic gabapentin, which can cost less than $14 for 90 capsules, he said.
For the trial, Allen's team randomly assigned about 720 patients with moderate to severe symptoms of restless legs syndrome to Lyrica versus Mirapex, or Mirapex versus an inactive placebo.
Over 12 weeks of treatment, patients taking Lyrica showed greater improvement in symptoms, compared with those taking placebo (about 71 percent versus 47 percent), the researchers found.
Moreover, over 40 or 52 weeks of treatment, significantly fewer patients taking Lyrica saw their condition worsen compared to those taking Mirapex (2 percent versus nearly 8 percent), the authors noted.
That finding suggests that worsening of the condition is caused by dopamine agonists, not a natural occurrence, the study authors pointed out.
"Restless legs syndrome is a progressive disease. The question is not do people get worse over time -- they do," Allen said. "But dopamine [agonists] make patients worse than they were before. We get people who have symptoms 24 hours a day, which is profoundly disturbing."
In terms of side effects, six of the patients taking Lyrica had suicidal thoughts, as did five taking Mirapex.
For more information on restless legs syndrome, visit the U.S. National Institute of Neurological Disorders and Stroke.