A fixed-dose , randomized , double-blind , @ week study was conducted in patients @-@ years of age , who were randomized by two strata : @ ) Patients with prior stimulant use randomized to placebo , edivoxetine @ mg/kg/day , @ mg/kg/day , or @ mg/kg/day arms in a @:@:@:@ ratio ; @ ) Stimulant-nave patients randomized to placebo , edivoxetine @ mg/kg/day , @ mg/kg/day , @ mg/kg/day , or osmotic-release oral system methylphenidate ( OROS MPH ) ( @-@mg / day based on body weight ) arms in a @:@:@:@:@ ratio .