Pharmacoeconomic comparison of ziprasidone with other atypical oral antipsychotic agents in schizophrenia

Abstract

Objective: to comparatively investigate – by means of computer simulations – the economic cost and clinical outcomes of five atypical oral antipsychotic agents (ziprasidone, olanzapina, risperidone, paliperidone and aripiprazolo).
Methods: a cyclical stochastic model representing patient evolution, taking into account main adverse reactions (akathisia, weight gain and extra-pyramidal ARs), drug efficacy on psychosis stabilization and probability of relapse, was developed. Ten different scenarios were compared, each starting with one of the considered antipsychotics, prescribed either at home or in a hospital setting. Switching to another medication was allowed until no untried drugs were available, in which case clozapine treatment or admission to a Psychiatric Therapeutic Rehabilitation Center were irreversibly assigned. Model inputs were probabilities of ARs, probabilities of stabilization and probabilities of destabilization (assumed equal for all); as well as costs attributable to drugs, hospitalization, outpatient care and costs adverse reactions in terms of concomitant medications. Sources for the inputs were the trials reported in the most recent literature (from the year 2000), selected based on the homogeneity of the observational period and antipsychotic dosage used.
Results: in each scenario, the hospitalization cost represented the highest component of the overall cost (approximately 67%). Assuming equal drug effectiveness, ziprasidone fared better than all other considered competitors, showing the lowest average annual costs per patient (and also the lowest average annual hospitalization costs) as well as the largest numbers of controlled months without adverse reactions, independently of the initial setting.
Conclusions: the most important determinant of total cost appears to be hospitalization, whose cost is about 600% higher than the medications cost. Medication effectiveness and tolerability remain however of utmost importance for the patients well being and reduction of hospitalization rate.