OBJECTIVES: Compliance with pharmacologic treatment in schizophrenia is directly associated with the successful control of the condition. The objective of this study is to estimate the cost-effectiveness of quetiapine XR in the treatment of schizophrenia compared to paliperidone (ER) and quetiapine IR. METHODS: Model: A Markov model, with three disease states (mild, moderate and severe) was constructed with a time horizon of 1-year, based on Edwards 2005. The analysis was performed from the Turkish healthcare payer perspective. Patient group: Adult patients with schizophrenia receiving treatment. Data sources: Clinical data were acquired from local and international literature. Resource use data were provided by an expert panel. Prices of medications and other costs related to treatment of schizophrenia were obtained from the Ministry of Health Drug Price List in November 2008, and the Price Lists of Social Security Institution in 2008, respectively. Outcomes: Clinical outcome was defined as the number of relapses and hospitalizations within one year period. Economic outcome was the calculated annual cost of disease. Only direct medical costs, i.e. treatment, laboratory examinations and healthcare, were considered. RESULTS: Total annual cost of disease is €1.450 for quetiapine XR, lower as compared to quetiapine IR (€1.653), quetiapine IR pool (€1,606) and paliperidone (€1.898). Annual hospitalizations rate is 1149 for quetiapine XR and paliperidone, and 1174 for quetiapine IR. Annual relapse rate is 2569 for quetiapine XR and paliperidone, and 2623 for quetiapine IR. Quetiapine XR, with its lower cost, is superior to paliperidone on cost-minimization manner. Quetiapine XR has dominated quetiapine IR on cost-effectiveness manner. Sensitivity analyses prove that results are quite robust. CONCLUSIONS: In the treatment of schizophrenia, quetiapine XR dominates quetiapine IR due to lower cost, reduced relapse and hospitalization rate and dominates paliperidone due to lower cost. REFERENCE: Edwards NC et al. Pharmacoeconomics 2005;23(Suppl. 1):75-89.