Last year, the US Food and Drug Administration approved the first drug specifically marketed for restless leg syndrome, and earlier this year, Mayo Clinic researchers reported that the drug Requip can significantly improve the annoying symptoms and improve sleep for many of the 20 million Americans who have the neurological problem. A similar drug called Mirapex is up for FDA review now.

Restless legs syndrome is not fatal, but it can be a life-wrecker. When people with the syndrome are at rest, or trying to sleep, they get creepy-crawly feelings in the legs that can sometimes be relieved — for a short time — by movement. This means that sufferers may get only get a few hours’ sleep a night. The syndrome is believed to involve abnormalities in iron metabolism and production of dopamine, a neurotransmitter, in parts of the brain that control movement.

Requip and Mirapex (already on the market to treat Parkinson’s disease) increase activity in dopamine cells, said Dr. John Winkelman, medical director of the Sleep Health Center at Brigham and Women’s Hospital, who consults for the manufacturers of both Requip and Mirapex.

The leader of the Requip study, Dr. Richard K. Bogan, chief medical officer of sleep medicine at the University of South Carolina School of Medicine, said the 12-week multi-center study involved about 350 patients, roughly half of whom received a placebo, or dummy drug, and half, Requip. Neither doctors nor the patients knew who was getting the real drug, which proved significantly better.

Drug companies have funded most of the research into these medications; this study was funded by GlaxoSmithKline, the maker of Requip.