Patients meeting eligibility criteria(mutation +ve and having EEG spikes), will be admitted to the Pediatric Clinical Research Unit at Johns Hopkins Hospital and will have pharmacokinetics of DM determined to establish that they are rapid metabolizers of the drug. The baseline studies on initial admission include neurological, neuropsychology,EEG, gastroenterology, Occupational and Physical therapy evaluations. If the subject is a rapid metabolizer they will be randomized to one of the three drug doses. They are contacted by telephone, weekly in the first month, and monthly thereafter. They will be examined by a neurologist at 2 weeks,1 month, and 3 months during the drug trial. At each of these visits they will also be monitored for changes in complete blood count (CBC), electrolytes, and EKG. At the end of the 6 month drug trial the patients will be readmitted to Johns Hopkins Hospital when all baseline studies are repeated. Cost of travel, hospitalization and interim tests are free to participants.