Purpose To evaluate the efficacy and safety of once-daily quetiapine extended release (XR) in patients with schizophrenia switched from other antipsychotics which were suboptimal due to insufficient efficacy or insufficient tolerability.

Methods:

This was a 12-week, open-label study conducted in the Chinese population in Taiwan. Quetiapine XR was administrated at 300 mg on day 1, 600 mg on day 2 and up to 800 mg after day 2. From day 8 until the end of the study, the dose of quetiapine XR was adjusted within 400-800 mg per day, depending on the clinical response and tolerability of the patients.

Inclusion Criteria:

• The participants who were aged from 20 to 65 years and met the diagnosis of schizophrenia according to Diagnostic and Statistical Manual of Mental Disorders, fourth edition, text revision (DSM-IV-TR) were eligible for the recruitment to the clinical trial.
• They also fulfilled the criteria including having a score of 4 (moderate) or greater on any of the 7 items of the Positive and Negative Syndrome Scale (PANSS) Positive Symptom Subscale and needed to switch from previous antipsychotics due to insufficient efficacy or insufficient tolerability.

Exclusion Criteria:

• Any DSM-IV-TR Axis I disorder other than schizophrenia, except comorbid obsessive-compulsive disorder, anxiety disorder, eating disorders or impulse control disorders if they had been stable and had not been primary focus of treatment over the previous 6 months
• An imminent risk of suicide or a danger to self or others
• Pregnancy or lactation
• Intolerance or lack of response to quetiapine IR
• Use of cytochrome P450 3A4 inhibitors or inducers in the 14 days preceding enrolment
• Administration of a depot antipsychotic injection within one dosing interval before recruitment
• Unstable or inadequately treated medical illness as judged by the investigator.