Blackwell Science, LtdOxford, UKPCNPsychiatry and Clinical Neurosciences1323-13162005 Blackwell Science Pty Ltd 2005594385394Original ArticlePharmacoeconomics of schizophreniaY. K. Yang et al.
Psychiatry and Clinical Neurosciences (2005), 59, 385–394
Regular Article
Pharmacoeconomic evaluation of schizophrenia in Taiwan: Model comparison of long-acting risperidone versus olanzapine versus depot haloperidol based on estimated costs YEN KUANG YANG, MD,1 YENG HUI TARN, PhD,2 TING YING WANG, M.Sc,3 CHIA-YIH LIU, MD,4 YI-CHENG LAIO, MD,5 YUAN-HWA CHOU, MD, PhD,6 SHIN-MIN LEE, MD,7 AND CHUN-CHIH CHEN, MD5 1
Department of Psychiatry, National Cheng Kung University College of Medicine, 2Department of Pharmacy, Taipei City Hospital and National Defense Medical Center, 3Department of Pharmacy Practice, Tri-Service General Hospital, 4Department of Psychiatry, Chang Gung Memorial Hospital and Chang Gung University School of Medicine, 5Department of Psychiatry, Changhua Christian Hospital, 6Department of Psychiatry, Taipei Veteran General Hospital and National Yang-Ming University, 7Department of Health, Bali Mental Hospital Taiwan
Abstract
Antipsychotics are the keystone in schizophrenia treatment. Although the benefits of the new generation of antipsychotics has been demonstrated over the last decade, the issues of patient compliance and higher purchasing price of atypical antipsychotics remain unresolved. Risperidone is the only atypical antipsychotic agent with long-acting formulation. Long-acting risperidone is a water-based injection and it has been associated with a low level of pain. The aim of the present study was to test whether an improvement in compliance with the use of a long-acting risperidone, compared with olanzapine and depot haloperidol, can increase the effectiveness and the costeffectiveness indexes. An economic comparison model with decision tree, rather than a prospective design with real clinical drug trial, was applied. The unit cost for each medical procedure was obtained from the claimed-database of the Bureau of National Health Insurance in Taiwan. An executive committee simulated the incidence of extrapyramidal side-effects and proposed a therapeutic model for each strategy based on a literature review. The probabilities of treatment response of different agents and those of different mental health states were estimated by the executive committee and 10 senior psychiatrists who were randomly selected. Sensitivity analysis was performed for drug cost-effectiveness and compliance improvement for using long-acting risperidone. The results showed that long-acting risperidone is more cost-effective than either olanzapine or depot haloperidol for treating schizophrenia patients whose conditions are stable and whose illness duration ranges from 1 to 5 years. The comparison model with the Kaplan–Meier decision tree may serve as an alternative to prospectively designed studies for cost-effectiveness of atypical antipsychotics.
Key words
long-acting antipsychotics, model comparison, pharmacoeconomic evaluation, schizophrenia.
INTRODUCTION Correspondence address: Dr Yen Kuang Yang, Department of Psychiatry, College of Medicine, National Cheng Kung University, 138 Sheng Li Road, Tainan 70428, Taiwan. Email:
[email protected] Received 7 July 2004; revised 20 January 2005; accepted 6 February 2005.
Schizophrenia is a serious and costly disorder because its course is chronic and it can have a major effect on the patient’s capacity for social adaptation and personality.1–5 Although many factors are involved in the treatment, antipsychotics are the keystone. The bene-
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fits of the new generation of antipsychotics (or atypical antipsychotics) have been demonstrated over the last decade in the therapeutic management of schizophrenia. Risperidone is the only atypical antipsychotic agent with a long-acting formulation; it is a waterbased injection that has been associated with a low level of pain.6–8 Modeled after the system in the USA, the mental health care system in Taiwan was implemented after World War II. Before World War II, the quality and quantity of mental health care were quite primitive. Initially, the development of mental hospitals for psychosis was a priority for those who were given up by their families. Psychiatric services in general hospitals were organized later. Currently, most of the healthcare costs, including that for the care of mental disorders, for each resident in Taiwan are reimbursed by Bureau of National Health Insurance (BNHI), which is the government-run national health insurance organization. The national health insurance program provides comprehensive coverage, including inpatient care, ambulatory care, laboratory tests, prescription drugs, and dental services, traditional Chinese medicine, day care for persons with mental illness, home care, and certain preventive services. By 1999, approximately 96% of Taiwan’s population was covered by the program of BNHI.9 Compared to conventional antipsychotics, atypical antipsychotics have higher prices and a better treatment profile.10 Therefore, pharmacoeconomic evaluations become very important in this regard. Assessing antipsychotics should involve analyzing their clinical effectiveness, safety and the costs in comparison to the use of medical resources.10 The most suitable design for a pharmacoeconomic study of antipsychotics is the prospective method. However, it has been estimated that it costs more than US$2m and takes more than 3 years to conduct a large-scale prospective pharmacoeconomic study in Taiwan. Hence, we applied the Kaplan–Meier method11 to compare to the medical costs for treating schizophrenia patients using long-acting risperidone, olanzapine and depot haloperidol. The aim of the present pharmacoeconomic evaluation was to determine which therapeutic strategy is the most effective, with acceptable cost. The economic impacts were measured in terms of cost to the BNHI in Taiwan and in terms of clinical effectiveness and safety criteria based on literature review or psychiatric experts’ estimation.
Y. K. Yang et al.
METHOD Executive expert committee The present study was conducted by an executive committee made up of six senior psychiatrists, two pharmacoeconomicists, and a representative from Janssen Pharmaceutical Taiwan. The role of the executive committee was to develop and validate a methodology for use in this pharmaeconomic assessment. The methodology included model type, target group (patient population), effectiveness criteria, unit costs of BNHI, clinical outcomes used, medical costs of different mental health states, variables tested in the sensitivity analyses, hypotheses and outcomes validation.
Type of study, model, and patient population In order to assess the economic implications of the different treatment strategies, a cost-effectiveness analysis with modeling technique comparing three therapeutic options for patients with schizophrenia was constructed. The model was a simple decision tree with three main branches corresponding to the three strategies, namely long-acting risperidone, olanzapine and depot haloperidol.12 The study simulated the treatment of a cohort of 1000 patients with schizophrenia, in which patients could change their treatment strategies according to their response/health status. This model comparison simulated the start of treatment of the patients with schizophrenia with up to three different types of antipsychotic: haloperidol, olanzapine and risperidone. The patient population/base case scenario, defined by the executive committee, was a group of stable schizophrenia patients whose scores on the Brief Psychiatric Rating Scale (BSRS)13 were
