Establishing a Dose-response Relationship for Oral Risperidone in Relapsed Schizophrenia

For many antipsychotics, dose-response relationships remain poorly understood. High dose treatment remains commonplace. We aimed to establish the dose-response relationship for oral risperidone in relapsed schizophrenia. We searched the known medical literature for fixed-dose studies of oral risperidone in this patient group. Data recovered were used to construct graphs of dose versus response. Eighteen reports evaluating the efficacy of oral risperidone were retrieved. Three studies used fixed doses of oral risperidone for eight weeks in relapsed schizophrenia. The data from these studies were included. Graphs plotted using these data strongly suggest that doses of around 4 mg daily are optimal. A dose of 2 mg daily consistently produced a lower level of efficacy. Doses of 6 mg or greater produced no additional benefit and doses tend to be less efficacious at 10mg daily and above. Frequency of extrapyramidal adverse effects increased with dose. The optimal dose of risperidone in relapsed schizophrenia is 4 mg daily. Higher doses are unlikely to improve efficacy and may reduce it. Adverse movement disorders become more common.