During this open-label, randomized, 4-week parallel-group study in pediatric patients, patients will be stratified by age (5-8 years and 9-17 years), and randomly assigned to one of 3 dose levels (30 mg/kg/day, 60 mg/kg/day, and 90 mg/kg/day) in the manner described in Section 3.5.1. Patients weighing less than 20 kg will not be assigned to the 30 mg/kg group, and patients weighing more than 60 kg will not be assigned to the 90 mg/kg group, due to dosing concerns. A total of 48 patients will be enrolled (8/treatment group/age stratum), with the expectation that 36 (6/treatment group/age stratum) will complete.