To the Editors: C lozapine, an atypical antipsychotic, Concentration-dose ratio was obtained by dividing the sum of plasma clozapine and total (clozapine and norclozapine) concentrations by clozapine dose.

The results show that aripiprazole might be generally well tolerated and might constitute an alternative treatment of subjects with ASD who experience poor efficacy or tolerability issues with risperidone treatment. Additional long-term controlled studies are needed to evaluate the efficacy and the safety of switching to aripiprazole from other antipsychotics in subjects with ASD.