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Curr Med Res Opin. 2013 Mar;29(3):227-39. doi: 10.1185/03007995.2012.762903. Epub 2013 Jan 22.

The long-term clinical benefit and effectiveness of switching to once-daily quetiapine extended release in patients with schizophrenia.

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  • 1Department of Psychiatry, Faculty of Medicine, University of Alberta, 9942-108 Street, Edmonton, Alberta T5K 2J5, Canada.



To evaluate the long-term clinical benefit and effectiveness of switching to once-daily quetiapine extended release (XR) from an oral antipsychotic in patients with schizophrenia. Reasons for switching included insufficient efficacy, tolerability, and/or non-acceptability. The primary endpoint was the percentage of patients achieving an improvement in Clinical Global Impression - Clinical Benefit (CGI-CB) scale scores.


A 24-week, international, multicentre, open-label, prospective study ( : NCT00640601). After a 7-14 day enrolment period (depending whether prior antipsychotic mono- or combination therapy), all patients received quetiapine XR 300 mg once daily (day 1), 600 mg/day (day 2), 600-800 mg/day (day 3) and 400-800 mg/day thereafter, with down-titration and discontinuation of prior antipsychotic by day 4.


A total of 62% of patients completed the study and 56.9% (LOCF, ITT) achieved a significant improvement in CGI-CB (95% CI [0.51, 0.63]; p = 0.02). Switches due to insufficient efficacy showed a significant improvement (60%, 95% CI [0.51, 0.68]; p = 0.02), compared to 54.4% ([0.44, 0.64]; p = 0.38) and 52.4% ([0.36, 0.68]; p = 0.76) of switches due to insufficient tolerability and non-acceptability respectively (both p = ns). Patients previously on olanzapine and quetiapine IR showed a significant improvement in CGI-CB (62.6% [p = 0.02] and 61.2% [p = 0.04], respectively). Somnolence (18.0%) and dizziness (14.6%) were the main adverse events. Anticholinergic use decreased from 7.1 to 2.7%. Overall mean weight gain was 0.4 kg; 12.9% of patients experienced a weight gain of ≥7% and 15% experienced a clinically relevant shift in triglycerides from baseline.


A majority of patients switched from other antipsychotics to quetiapine XR experienced clinical benefit. This was supported by all other efficacy outcomes regardless of the reason for switching. Safety data confirmed quetiapine XR was safe and well tolerated. The open-label design and lack of a placebo group represent limitations.

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