ORIGINAL ARTICLESEvaluation of the feasibility of switching from immediate release quetiapine to extended release quetiapine fumarate in stable outpatients with schizophreniaMöller, Hans-Jürgena; Johnson, Sunnyb; Mateva, Temenuzhkac; Brecher, Martind; Svensson, Olae; Miller, Franke; Meulien, Didiereon behalf of the Study 146 investigatorsAuthor Information aPsychiatric Hospital of the University of Munich, Munich, Germany bCredit Valley Hospital, Mississauga, Ontario, Canada cDistrict Dispensary for Psychiatric Disorders, Rousse, Bulgaria dAstraZeneca Pharmaceuticals, Wilmington, Delaware, USA eAstraZeneca R&D, Södertälje, Sweden Correspondence to Prof Hans-Jürgen Möller, MD, Psychiatric Hospital of the University of Munich, Nussbaumstr. 7, 80336 Munich, Germany Tel: +49 89 5160 5501; fax: +49 89 5160 5522; e-mail: email@example.com Received 2 March 2007 Accepted 1 October 2007 International Clinical Psychopharmacology: March 2008 - Volume 23 - Issue 2 - p 95-105 doi: 10.1097/YIC.0b013e3282f2d42c Buy Metrics Abstract This double-blind, double-dummy study (D1444C00146) evaluated the efficacy and safety of switching patients with clinically stable schizophrenia from quetiapine immediate release (IR) to the same dose of once-daily extended release quetiapine fumarate (quetiapine XR). Patients received quetiapine IR 400–800 mg/day twice daily for 4 weeks, and were then randomized (2 : 1) to a once-daily equivalent dose of quetiapine XR or maintained on IR for 6 weeks. The primary variable was the proportion of patients who discontinued treatment owing to lack of efficacy or whose Positive and Negative Syndrome Scale scores increased by at least 20% from randomization to any visit. In total, 497 patients were randomized to quetiapine XR (n=331) or IR (n=166). Noninferiority (6% margin; one-sided test, 2.5% significance level) was narrowly missed for the primary efficacy variable for the modified intention-to-treat population (9.1%, quetiapine XR; 7.2%, quetiapine IR; difference 1.86%; 95% confidence interval: −3.78, 6.57; P=0.0431), but was shown for the per-protocol population (5.3%, quetiapine XR; 6.2%, quetiapine IR; difference: −0.83%; 95% confidence interval: −6.75, 3.71; P=0.0017). Serious adverse event incidence was low for quetiapine XR and IR; there were no unexpected adverse events. In conclusion, efficacy was maintained without compromising safety/tolerability when switching patients with stable schizophrenia from twice-daily quetiapine IR to once-daily quetiapine XR (400–800 mg/day). © 2008 Lippincott Williams & Wilkins, Inc.