Aripiprazole: dose-response relationship in schizophrenia and schizoaffective disorder.

Aripiprazole is an atypical antipsychotic that has been shown to be more effective than placebo and at least as effective as haloperidol and risperidone in the treatment of schizophrenia and schizoaffective disorder. Despite having a well defined licensed dose range, the optimum dose for aripiprazole is yet to be established. Aripiprazole exhibits high affinity for dopamine D(2) receptors, with near maximal receptor occupancy at a dose of 30 mg. Even doses as low as 2 mg, thought not to be clinically effective, have produced striatal D(2) receptor occupancies exceeding 70%, higher than the accepted threshold for antipsychotic effect. In this review we examined the efficacy data from short-term studies of aripiprazole in relapsed schizophrenia or schizoaffective disorder, in order to establish a dose-response relationship for aripiprazole. Results of five fixed-dose studies suggest that the threshold for clinical effect is between 5 and 10 mg/day. In addition, the highest response rate is seen at 10 mg/day. Doses above 20 mg/day do not appear to provide any additional benefit and may be associated with a smaller change in symptom scores. In summary, the data available so far indicate that the optimum dose for aripiprazole is 10 mg/day and that doses above 20 mg/day provide no additional benefit.