Pharmacoeconomics of long-acting risperidone: results and validity of cost-effectiveness models.

Relapse is the primary cost driver in schizophrenia and is closely related to levels of adherence (compliance) with therapy. Both atypical antipsychotic agents and depot preparations have been shown to be useful in improving therapeutic adherence compared with oral conventional antipsychotic agents. Long-acting risperidone is a new formulation of an atypical antipsychotic agent that combines the pharmacological advantages of the atypical drugs with those of its mode of administration. The likelihood of improved compliance compared with existing treatment regimens implies that the higher acquisition costs would be offset by reduced rates of relapse. Economic models, which represent the health and economic outcomes of patients or populations under a variety of scenarios, are used to evaluate the economic implications of schizophrenia treatment. These models need to reflect clinical reality while simultaneously remaining as simple as possible. The assumptions and results need to be made transparent; data quality must be described explicitly; areas of uncertainty must be comprehensively explored through sensitivity analysis; and individual models must be validated, for example by comparing them with others in the therapeutic area. In this article, cost-effectiveness models of long-acting risperidone developed for different countries are discussed in terms of design, data sources and robustness, and the implications of the results for the treatment of schizophrenia are also reviewed. A discrete event simulation (DES) model that was developed using UK cost and treatment assumptions, in order to provide a 'proof of concept', is described. Country-specific models forthe United States, Canada, Germany, the Netherlands, France, Belgium, Italy and Portugal, using either DES or decision analytical structures, are then discussed. Comprehensive sensitivity analyses were conducted to assess the robustness of the results. In each case, long-acting risperidone produced additional clinical benefit and cost savings compared with other treatment strategies, despite significant variations in cost effectiveness and therapeutic approaches. In particular, improved adherence arising through the use of long-acting risperidone provides a cost-effective strategy for treating patients with schizophrenia, irrespective of the country analysed. The information generated in this analysis therefore provides one potential method for improving resource allocation and reducing the health burden related to schizophrenia.