• Changes in the Clinical Global Impression - Severity of Illness subscale (CGI-S) from baseline to endpoint, compared between treatment groups
  

• Changes from baseline in the YMRS, MADRS and HAM-A at Months 1 - 6 and endpoint; resource utilization (emergency room visits, hospitalizations); quality of life; patient satisfaction with treatment; time to intervention for manic and depressive episodes
  

This an open-label, randomized study. Approximately 40 stable bipolar patients who are on an atypical antipsychotic (olanzapine, risperidone, quetiapine) plus adjunct bipolar treatment consisting of (a maximum or two of lithium, valproate or lamotrigine, and, if applicable, one antidepressant) will be randomized to two arms. In one arm, 25 milligrams of long-acting injectable risperidone will replace the oral atypical antipsychotic as adjunct therapy and in the other arm, patients will continue with their current atypical antipsychotic therapy. Trial duration is 6 months. In the long-acting injectable risperidone arm, the oral atypical antipsychotic will be continued (as supplementation) for 3 weeks after the first injection of long-acting risperidone and then discontinued. Investigators, based upon the patient's response, may increase the dose of injectable risperidone to 37.5 mg after 6 weeks on the 25-mg dose and to 50 mg after at least 4 weeks on the 37.5-mg dose. Risperidone oral supplementation is allowed. In the oral antipsychotic only arm, the oral atypical antipsychotic dose can also be increased as required. The primary efficacy outcome will be measured by changes in the Clinical Global Impression - Severity of Illness subscale (CGI-S), from baseline to endpoint, and will be compared between the treatment groups. Safety will be monitored throughout the study. The primary hypothesis is that patients switched to long-acting injectable risperidone will be able to tolerate this formulation of risperidone and maintain or even improve their reduction in bipolar symptomatology compared with baseline, and compared with subjects who continue in the oral antipsychotic arm. The secondary hypothesis is that patients switched to long-acting injectable risperidone will have a longer time to intervention for a mood episode (either mania or depression) as compared with subjects who continue in the oral antipsychotic arm. Risperidone, formulated for intramuscular injection, 25 mg every 2 weeks. Patients treated with injectable risperidone continue their original oral atypical antipsychotic (AAP) dose for 3 weeks. Investigators, at their discretion, may increase the dose of injectable risperidone to 37.5 mg after 6 weeks on the 25-mg dose and to 50 mg after at least 4 weeks on the 37.5-mg dose. Study duration is 6 months.