Spotlight on long-acting risperidone in schizophrenia

Long-acting risperidone (Risperdal Consta?) is a novel, intramuscular formulation of the atypical antipsychotic risperidone, which has shown efficacy in the treatment of patients with schizophrenia. Long-acting risperidone is pharmacokinetically equivalent to and causes less plasma drug concentration fluctuation than the oral formulation. This novel formulation is an aqueous suspension of microspheres comprising risperidone and a biodegradable copolymer. Significant release of risperidone from the microspheres begins 3 weeks after the first injection; thus, administration of another antipsychotic is necessary during this period only. Steady-state plasma concentrations are reached after the fourth injection. Elimination is complete 7–8 weeks after the last injection. Long-acting risperidone 25 or 50mg every 2 weeks demonstrated significantly greater antipsychotic efficacy than placebo and equivalent efficacy to oral risperidone 2–6 mg/day in two randomized, double-blind, double-dummy, 12-week trials of patients with schizophrenia. Additionally, in one of these trials, improvements in health-related quality of life (HRQOL) were superior with long-acting risperidone than placebo. Compared with baseline, improvements in the symptoms of schizophrenia in stable patients were significant with long-acting risperidone 25 or 50mg (12-month trial) and 25, 37.5 or 50mg (12-week trial) every 2 weeks, in two noncomparative, multicenter trials. Patient satisfaction with their medication and patient HRQOL mental health scores improved significantly in the 12-month trial. Long-acting risperidone is generally well tolerated, with a low incidence of injection site pain and an otherwise similar profile of adverse effects to the oral formulation. The overall incidence of extrapyramidal disorders in clinical trials was low (≤10%) with similar, yet minimal, changes in extrapyramidal symptom severity between patients treated with long-acting risperidone, oral risperidone or placebo. Tardive dyskinesia was reported in the 12-month trial, in 0.7% of patients. Conclusion: Long-acting risperidone is effective and generally well tolerated in patients with schizophrenia, including those patients with stable symptoms. Long-acting risperidone is the first atypical antipsychotic vailable in a formulation which offers a sustained, steady release of drug and is thus an attractive, new option in the treatment of patients with schizophrenia.