At 2 h after dosing , risperidone plasma concentrations were 1.54 + / -0.99 ng/ml and 2.80 + / -1.41 ng/ml ; 9-hydroxy-risperidone concentrations were 0.77 + / -0.46 ng/ml and 1.54 + / -0.85 ng/ml after intake of 0.25 mg and 0.5 mg doses , respectively .
