Enrolled children went through four study phases : @ ) Screening period ( @ weeks ) and a @ day medication washout period ; @ ) open-label period with dose initiation of MPH-MLR @mg daily and individual dose optimization treatment period ( @-@ weeks ) ; @ ) double-blind crossover period in which participants were randomized to sequences ( @ week each ) of placebo and the optimized MPH-MLR dose given daily ; and @ ) follow-up safety call .