Cost-effectiveness analysis of schizophrenia relapse prevention : an economic evaluation of the ZEUS (Ziprasidone-Extended-Use-In-Schizophrenia) study in Spain

Abstract

Objective: The aim of this study was to estimate the cost-effectiveness of schizophrenia relapse prevention in Spain using data from the ZEUS (Ziprasidone-Extended-Use-in-Schizophrenia) study.

Methods: Treatment of schizophrenia was modeled over 1 year using a retrospective deterministic model from the Spanish National Health System (NHS) perspective (year 2005). The primary outcome was the probability of relapse occurring within a 52-week period of treatment with daily doses of ziprasidone 40-160mg versus placebo. Data were obtained from a randomised, double-blind clinical trial (n = 218 patients). Antipsychotic cost, concomitant medications to treat adverse events (for example extrapyramidal symptoms) and medical costs associated with adverse events were derived from the clinical trial results and a Spanish health cost database. The average cost of a relapse admitted to hospital in Spain (3421 euro) was obtained from a retrospective study.

Results: The probability of psychosis relapse was 0.77 with placebo, and 0.43, 0.35, 0.36 and 0.38 with ziprasidone daily doses of 40, 80, 160mg and average dose, respectively (p < 0.01 vs placebo in all cases). The average annual incremental cost per relapse avoided was 186 euro for the average dose, ranging from a saving of 557 euro (80 mg/day) to an incremental cost of 1015 euro (160 mg/day), and was lower in all cases than the minimum cost of a relapse (2830 euro).

Conclusions: According to this evaluation, psychosis relapse prevention with ziprasidone is cost effective compared with no treatment from the Spanish NHS perspective. Ziprasidone therapy avoids a considerable number of relapses at a reasonable cost, producing cost savings.