Long-term symptomatic remission of schizophrenia with once-daily extended release quetiapine fumarate: post-hoc analysis of data from a randomized withdrawal, placebo-controlled study.

Despite available effective medications, many patients with schizophrenia do not become completely symptom free. We report analyses of data from a randomized, double-blind, placebo-controlled relapse prevention study of extended release quetiapine fumarate (quetiapine XR) using Remission in Schizophrenia Working Group criteria for symptomatic remission. During 16-week open-label stabilization, patients with stable schizophrenia were switched from their current antipsychotic to quetiapine XR (400, 600 or 800 mg/day flexibly dosed). One hundred and ninety-seven patients were randomized to either quetiapine XR or placebo (planned for 1 year or until relapse). The study was terminated early because the planned interim analysis showed quetiapine XR to be statistically superior to placebo in the primary outcome variable (time to schizophrenia relapse). One hundred and eighty of 195 (92.3%) patients with an available Positive and Negative Syndrome Scale assessment met symptomatic remission criteria at randomization (following 16 weeks' quetiapine XR). The risk of losing symptomatic remission was statistically significantly higher with placebo versus quetiapine XR: hazard ratio 0.39 (95% confidence interval: 0.19-0.81, P=0.009), that is, 61% risk reduction for quetiapine XR-treated versus placebo-treated patients. At 6 months postrandomization, the probability that patients would be in remission was 76% for quetiapine XR and 52% for placebo. Once-daily quetiapine XR was effective in preserving symptomatic remission in the longer-term treatment of patients with schizophrenia.