"The U.S. Food and Drug Administration FDA said it had approved Adamas Pharmaceuticals Incs treatment for a side effect caused by a commonly prescribed Parkinsons drug sending the shares of the drugmaker soaring in aftermarket trading.  The companys shares were up . percent at . after the bell on Thursday.  A majority of patients diagnosed with Parkinsons are treated with levodopa whose use often leads to dyskinesia  involuntary movements that are nonrhythmic purposeless and unpredictable.  Parkinsons disease is a debilitating disorder in which brain cells progressively die causing patients to experience tremors rigidity extreme slowness of movement impaired balance and difficulties in swallowing and speaking.  Adamas Gocovri previously ADS is the first drug cleared by the FDA to control levodopainduced dyskinesia LID. The longacting therapy is taken oncedaily at bedtime.  An estimated  percent of levodopatreated patients about  people in the United States suffer from LID the company said.  Fluctuating levels of levodopa result in erratic periods of muscular control and involuntary movements throughout the day disrupting activity at least half a dozen times a day.  As Parkinsons progresses patients are dyskinetic just after taking levodopa but increasingly exhibit off time or worsening symptoms as it wears off.  These patients have little recourse other than opting for deep brain stimulation a surgical procedure that involves blocking electrical signals from targeted areas in the brain.  With Gocovri which targets both dyskinesia and off time patients will be able to reclaim about . hours of their day CEO Gregory Went said in an interview ahead of the decision.  About  people are diagnosed with Parkinsons in the United States each year according to the National Institutes of Health.  The main ingredient of Gocovri amantadine has been available in the market as an antiviral drug for several decades.  The company said the drug is expected to be available in the fourth quarter and formally launched in January .  Adamas is also testing the drug to treat walking impairment in patients with multiple sclerosis."