150mg per 6 hours = 600mg per day (150mg x 24hours/day ÷ 6hours/dose)
child weighs 30p = 30 ÷ 2.2p/Kg = 13.6Kg
recommended dosage = 20mg (low)/Kg/day = 20mg x 13.6Kg = 272mg/day
recommended dosage = 40mg (high)/Kg/day = 40mg x 13.6Kg = 544mg/day
so, 600mg will exceed the recommendation
a safe dose is one that will fall within the range of 20-40 mg/kg/day