Results from studies of older long-acting injectable antipsychotics (not risperidone) show that patients tend to relapse (which means start having symptoms again) when they are given low doses. However, increasing the dose may cause more side effects. This study will measure the time to relapse during a 52-week period in patients with schizophrenia or schizoaffective disorder who are switched from an oral antipsychotic (one taken by mouth) to one of two doses of long-acting risperidone injections (shots). The patients will be assigned to a dose of either 25 or 50 milligrams per injection every 2 weeks. Patients continue to take their usual oral antipsychotic medications up to 3 weeks following the first injection. After this 3-week period, they will receive the injectable risperidone only. Patients will be asked questions at each visit to help determine the effectiveness of the drug as assessed by the Clinical Global Impression Scale and the Positive and Negative Syndrome Scale. The safety of the drug will be based on patient signs and symptoms assessed according to the Extrapyramidal Symptom Rating Scale and self-reported treatment-emergent adverse events. Long-acting risperidone injection, 25 or 50 milligrams per injection, every 2 weeks for 52 weeks. Patients will continue to take their current oral antipsychotics for up to 3 weeks following the first injection of risperidone.
