Clinical review of a long-acting, injectable formulation of risperidone

Background: A long-acting, injectable risperidone formulation is the first depot atypical antipsychotic drug to become available in the United States. Objective: The intent of this article is to review the efficacy and safety data available for long-acting, injectable risperidone. Methods: Information was identified via MEDLINE (years, 1990-May 2004) using the terms risperidone, long-acting injectable, depot, and delayed-action preparations. The manufacturer also provided information about risperidone in the form of abstracts and summaries of professional meetings. Results: Several 12-week studies and one 12-month study suggest that long-acting risperidone is an effective and well-tolerated treatment option for the maintenance therapy of schizophrenia. Thus far, no unexpected adverse events have been reported with the long-acting formulation. Extrapyramidal symptoms with long-acting risperidone were uncommon, dose-related, and similar to those observed with oral risperidone in short-term trials. A small, dose-related weight gain occurred with long-acting risperidone, again similar to that seen with oral risperidone. Pain at the injection site was uncommon and decreased with continued administration. The long-acting, injectable formulation comes in an aqueous suspension of microspheres. There is no initial drug release after injection; the main release of risperidone begins at week 2 to 3 postinjection, increases during weeks 3 and 4, is maintained during weeks 4 through 6, and declines between weeks 6 and 7. With repeated injections every 2 weeks, steady-state levels are usually reached by weeks 6 to S. For most patients, the initial dosage should be 25 mg every 2 weeks, and oral administration should continue for the first 3 weeks after initial injection. Doses can be increased every 8 weeks to a maximum of 50 mg every 2 weeks. Conclusion: Long-acting risperidone offers clinicians a combination of the benefits of a depot antipsychotic drug with the therapeutic advantages of an atypical antipsychotic drug. (C) 2004 Excerpta Medica, Inc.