Parkinson's drug could treat restless leg syndrome

A drug prescribed for Parkinson's disease may also treat restless leg syndrome without the adverse side effects of current therapies, Medical College of Georgia researchers say.

Rasagaline works by prolonging the effect of dopamine, a chemical that transmits signals between nerve cells in the brain. The cause of RLS is unknown, but research suggests a dopamine imbalance. Parkinson's is caused by a dopamine insufficiency.

"The hope is that Rasagaline, because it prolongs the effect of existing dopamine, instead of producing more, will not come with adverse side effects," said Dr. Shyamal Mehta, an MCG neurologist and neuroscientist. "We are trying to evaluate its safety and efficacy in treating RLS at this point. When it has been used to treat Parkinson's, it's been well-tolerated with few side effects."

Current RLS therapies include a group drugs that work by activating existing dopamine receptors, prompting the brain to make more dopamine. The problem, Mehta said, is that those drugs usually come with adverse effects, because dopamine increases feelings of euphoria.

"People taking those drugs often report behavioral problems like addiction, because the pleasure they get from things like shopping is multiplied," he said. "They can cause impulse-control problems, like gambling or hypersexuality as well. They can also cause increased sleepiness and sudden sleep attacks, which can be quite disruptive and dangerous."

Some reports also suggest decreased efficacy after extended use, as well as symptoms beginning earlier in the day.

Restless leg syndrome, which affects 10 percent of the population, is characterized by prickling or tingling in the legs and an urge to move the legs. Symptoms are more noticeable at rest, such as during bedtime or a long car ride. RLS can also cause depression and daytime sleepiness, Dr. Mehta said, and is linked to conditions including iron deficiency, renal failure, pregnancy and Parkinson's.