Poor adherence to antipsychotics is a major problem in long term treatment of schizophrenia, a relationship between poor adherence and relapse is well documented in the literature. One of the factors that may affect compliance is antipsychotic formulation. The primary objective of the study was to compare patient preference for olanzapine conventional tablet (OCT) with orodispersible tablet (ODT) as measured by a formulation preference question.

A 12-week open label, randomized, crossover, multinational study (Turkey, Romania, Israel, Brazil, Mexico) conducted to estimate the proportion of patients preferring OCT over ODT after 6 weeks of treatment with each formulation. Outpatients with stable schizophrenia (CGI-S<4) on OCT monotherapy for at least 1 month before study inclusion were randomized 1:1. Compliance, drug attitude were measured using DAI-10 and MAF scales; tolerability and safety by AMDP-5 questionnaire and adverse event summary.

From 265 randomized patients,207 were eligible for the analysis and 175 patients answered the preference question. 106(61%) patients preferred ODT, and 48(27%) preferred OCT (p<0.001 adjusted for treatment sequence); 21(12%) expressed no preference. 90% of patients were rated as almost always compliant on both formulations. The adverse event profiles of ODT and OCT were similar: most common (>1%) adverse events were weight increase, hypertriglyceridaemia, and somnolence.

Most of the patients who answered the preference question declared to prefer olanzapine orodispersible to conventional formulation. Given the importance of patient's preference as one of the factors for future compliance, olanzapine orodispersible tablet could be a good choice.