Evaluation of the Efficacy and Safety of Risperidone Injections Given Once a Month to Adults With Schizophrenia or Schizoaffective Disorder

Risperidone, taken by mouth on a daily basis, has been an effective treatment for schizophrenia and schizoaffective disorder. Risperidone is also available in a long-acting injectable form so that patients can take their medicine by bi-weekly injections. This study will assess the effectiveness and safety of long-acting risperidone injection given once a month instead of every two weeks (based on previous studies with dosing every 2 weeks). During the four-week lead-in phase, patients will receive one 50-milligram injection every two weeks for two doses. Patients continue to take their prescribed dose of risperidone tablets (from 2 to 6 milligrams per day) for the first 14 days. After the first month, patients will receive one 50-milligram injection once a month for 48 weeks. This dose can be increased to 75 milligrams if patient meets relapse criteria, and is willing to stay in the trial. Patients will be asked questions to help determine how well the monthly injections are working. Laboratory tests (including drug levels), physical examinations and adverse event reporting will be performed to determine the safety of the monthly injections. Risperidone oral tablets, 2 to 6 milligrams per day, for first 2 weeks; long-acting risperidone intramuscular injections, 50 mg in 2 milliliters of liquid, every 2 weeks for 1 month, then injections once a month for 48 weeks. Monthly injection dose may be increased to 75 mg in 2-mL if needed.