A fixed-dose , randomized , double-blind , 8 week study was conducted in patients 6-17 years of age , who were randomized by two strata : 1 ) Patients with prior stimulant use randomized to placebo , edivoxetine 0.1 mg/kg/day , 0.2 mg/kg/day , or 0.3 mg/kg/day arms in a 1:1:1:1 ratio ; 2 ) Stimulant-nave patients randomized to placebo , edivoxetine 0.1 mg/kg/day , 0.2 mg/kg/day , 0.3 mg/kg/day , or osmotic-release oral system methylphenidate ( OROS MPH ) ( 18-54mg / day based on body weight ) arms in a 1:1:1:1:1 ratio .