Initially the two dose range were 0.15-0.4 mg/day and 1.5-4mg/day but were changed in protocol amendment to evaluate the maximum tolerated dose with a minimum of 3.5mg/day and maximum of 6mg/day (resp. 0.35 and 0.6mg/day in low dose treatment arm) Risperidone lower dose (0.35-0.6 mg/day [subjects >=50kg] or 0.007-0.012 mg/kg/day [subjects <50 kg]) as 0.1 mg/mL oral solution or risperidone higher dose (3.5-6 mg/day [subjects >=50 kg] or 0.07-0.12 mg/kg/day [subjects <50 kg]) as 1 mg/mL oral solution for 8 weeks. Daily dose can be given all at once or through 2 administrations (in morning and evening); the dose is increased based on efficacy and tolerability.