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Schizophrenia is one of the most expensive psychiatric conditions because of high direct and indirect costs associated with the nature of the illness, its resistance to treatment and the consequences of relapse. Long-acting risperidone is a new formulation of an atypical antipsychotic drug that also offers the improvements in compliance associated with haloperidol depot. The aim of this simulation study was to compare the benefits and costs of three pharmacological treatment strategies comprising first-line treatment with long-acting risperidone injection, a haloperidol depot or an oral atypical antipsychotic agent, over a 5-year period in Germany. A discrete event simulation model was developed to compare three treatment scenarios from the perspective of major third-party payers (sickness funds and social security 'Sozialversicherung'). The scenarios comprised first-line treatment with haloperidol depot (scenario 1), long-acting risperidone (scenario 2) and oral olanzapine (scenario 3). Switches to second or third-line options were allowed when side-effects occurred or a patient suffered more than a fixed number of relapses. The model accounted for fixed patient characteristics, and on the basis of these, simulated patient histories according to several time-dependent variables. The time horizon for this model was limited to 5 years, and in accordance with German guidelines, costs and effects were discounted by between 3 and 10%. Direct costs included medication, type of physician visits and treatment location. Indirect costs were not included. Information on treatment alternatives, transition probabilities, model structure and healthcare utilization were derived from the literature and an expert panel. Outcomes were expressed in terms of the number and duration of psychotic episodes, cumulative symptom scores, costs, and quality-adjusted life-years (QALY). Univariate sensitivity analyses were carried out, as were subgroup analyses based on disease severity and for patients at high risk of being non-compliant. The long-acting risperidone strategy was calculated to avoid 0.23 and 0.33 relapses per patient, decrease the cumulative symptom score by 25 and 33 points, and decrease the costs by 2017 Euro and 6096 Euro per patient (1608 Euro and 5422 Euro discounted), compared with the haloperidol depot and olanzapine strategies, respectively, over a 5-year period (year of costing 2004). Among high-risk non-compliant patients, long-acting risperidone was estimated to avoid 0.23 and 0.47 relapses and save 4822 Euro and 10,646 Euro per patient (4107 Euro and 9490 Euro discounted), compared with the haloperidol depot and olanzapine strategies, respectively. Sensitivity analyses showed that the results were robust and mainly sensitive to changes in the reported relative effectiveness of atypical and conventional formulations for preventing symptom recurrence, and in the relative compliance with oral and long-acting formulations. In this model, long-acting risperidone is a dominant strategy compared with a haloperidol depot or oral atypical antipsychotic agent, being both more effective and less costly over a 5-year period. Results for long-acting risperidone are even more favourable among patients at high risk of being noncompliant or with more severe disease.

Schizophrenia is a chronic, relapsing disease that requires more healthcare resources to manage than any other single psychiatric illness. The main cost of treatment is hospitalization as a result of the exacerbation of symptoms often caused by poor compliance. Although the costs of hospitalization and relapse have been well documented, the differential effects of various medications on healthcare expenditure are still being determined. The aim of the present study was to estimate the cost effectiveness of long-acting risperidone in the treatment of high-risk, non-compliant patients with schizophrenia over a 5-year period in Canada. A discrete event model was developed comparing three scenarios, each with a different starting treatment: haloperidol depot, long-acting risperidone or oral risperidone. Second and third-line treatment options were olanzapine and clozapine, respectively, for all three scenarios. On the basis of 3000 simulated patient characteristics, the model generated individual patient histories. Outcomes included the number and duration of psychotic episodes, the cumulative Positive and Negative Syndrome Scale (PANSS) score and direct medical costs. The time horizon of the model was 5 years and a 5% discount rate was used for costs and effects. The perspective of the model was that of the Canadian healthcare system. After 5 years, treatment with long-acting risperidone saved Canada dollars 6908 and Canada dollars 13,130 (discounted) and avoided 0.28 and 0.54 relapses per patient, compared with haloperidol depot and oral risperidone, respectively. In this model, initiating treatment of high-risk, non-compliant patients with schizophrenia with long-acting risperidone was the dominant strategy. With long-acting risperidone, direct costs were lower and clinical effectiveness was greater, compared with haloperidol depot or oral risperidone, during years 4 and 5.

In schizophrenia, modelling techniques may be needed to estimate the long-term costs and effects of new interventions. However, it seems that a simple direct link between symptoms and costs does not exist. Decisions about whether a patient will be hospitalized or admitted to a different healthcare setting are based not only on symptoms but also on social and environmental factors. This paper describes the development of a model to assess the dependencies between a broad range of parameters in the treatment of schizophrenia. In particular, the model attempts to incorporate social and environmental factors into the decision-making process for the prescription of new drugs to patients. The model was used to analyse the potential benefits of improving compliance with medication by 20% in patients in the UK. A discrete event simulation (DES) model was developed, to describe a cohort of schizophrenia patients with multiple psychotic episodes. The model takes into account the patient's sex, disease severity, potential risk of harm to self and society, and social and environmental factors. Other variables that change over time include the number of psychiatric consultations, the presence of psychotic episodes, symptoms, treatments, compliance, side-effects, the lack of ability to take care of him/herself, care setting and risk of harm. Outcomes are costs, psychotic episodes and symptoms. Univariate and multivariate sensitivity analyses were performed. Direct medical costs were considered (year of costing 2002), applying a 6.0% discount rate for costs and a 1.5% discount rate for outcome. The timeframe of the model is 5 years. When 50% of the decisions about the patient care setting are based on symptoms, a 20% increase in compliance was estimated to save 16,147 pounds and to avoid 0.55 psychotic episodes per patient over 5 years. Sensitivity analysis showed that the costs savings associated with increased compliance are robust over a range of variations in parameters. DES offers a flexible structure for modelling a disease, taking into account how a patient's history affects the course of the disease over time. This approach is particularly pertinent to schizophrenia, in which treatment decisions are complex. The model shows that better compliance increases the time between relapses, decreases the symptom score, and reduces the requirement for treatment in an intensive patient care setting, leading to cost savings. The extent of the cost savings depends on the relative importance of symptoms and of social and environmental factors in these decisions.