Restless Legs Syndrome Drug Receives FDA Approval

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Seventy-four-year-old Marilyn Butterfield shakes her legs when she sits down for dinner. She shakes her legs when she sits down to read, and she shakes her legs in her bed when she lies down to sleep.

She's that woman who is standing at the back of the movie theater to watch a movie, because she can't bear to sit still for two hours.

The Peoria, Ariz., resident and retired nurse has had the sensory motor neurologic abnormality since childhood, but it's been especially bad for the last 15 years. When Butterfield sits still, she said it feels like a pressure builds in her knee joints that can't be relieved unless she moves her legs. 

"It sounds simple or blasé, but when you get the symptoms, it's so aggravating and so irritating especially if you're in a theater or at lunch or dinner and you have to get up," Butterfield told MyHealthNewsDaily. "It impacts your whole life."

Butterfield takes one of the two medications approved by the Food and Drug Administration (FDA) for restless legs syndrome, but she has cycled through several drugs over the years because they tend to stop being effective.

But now, she has a third drug option to explore, because the FDA this week approved the drug Horizant for treating the disorder.

About the drug

Horizant, which is manufactured by GlaxoSmithKline and XenoPort Inc., is recommended for once-daily use for people with moderate to severe restless legs syndrome. It was shown to be effective in two 12-week clinical trials, where patients on the drug had their symptoms measured with an objective scale, and then compared with those taking a placebo, according to the FDA.

The drug contains gabapentin enacarbil, a molecule that is similar to one in drugs that treat seizures in people with epilepsy, said Dr. Richard K. Bogan, who is one of the clinical investigators of the drug and president and medical director of SleepMed Inc. of South Carolina, a company that offers diagnostic services and therapy devices for sleep patients.

Horizant is an extended release drug, which means it's designed to be absorbed slowly throughout the night so that it has a longer duration of activeness, Bogan said. It was designed to be absorbed this way because restless legs syndrome symptoms tend to be worse in the evening hours, he said.

"It has a duration of action that covers when the patient has the circadian [time-related] symptoms," Bogan told MyHealthNewsDaily.

However, people who tend to sleep during the day and are awake at night are advised against taking the drug, according to the FDA.

A look at the syndrome

Scientists don't yet know the exact cause of restless legs syndrome, though the disorder tends to be genetic, according to the National Institutes of Health. In Butterfield's case, her father and brother also have the disorder.

Researchers also think that low iron levels in the brain could contribute to the syndrome, according to the NIH. 

Up to 10 percent of people in the United States have some form of restless legs syndrome, and 2 percent to 3 percent have moderate to severe versions of the syndrome, according to the NIH. Some cases are mild, involving slight discomfort, while others are severe and can be painful.

Even though the new drug can't cure the disorder, "having a new medication on the market is going to give us another option, and we need that option," Butterfield said.

Pass it on: The FDA approved this week a new drug for treating restless legs syndrome.

Follow MyHealthNewsDaily staff writer Amanda Chan on Twitter @AmandaLChan.

This story was provided by MyHealthNewsDaily, a sister site to LiveScience.

Amanda Chan
Amanda Chan
Amanda Chan was a staff writer for Live Science Health. She holds a bachelor's degree in journalism and mass communication from the Walter Cronkite School of Journalism and Mass Communication at Arizona State University, and a master's degree in journalism from Columbia University.