Efficacy and tolerability of quetiapine in patients with schizophrenia switched from other antipsychotics.

OBJECTIVE The Seroquel Patient Evaluation on Changing Treatment Relative to Usual Medication (SPECTRUM) study assessed the efficacy and tolerability of quetiapine (Seroquel™) in patients with schizophrenia switched from treatments providing suboptimal outcomes. METHODS This was an international, open-label, non-comparative study, designed with titration to 400 mg/day quetiapine over 7 days, then flexible dosing (300-750 mg/day) for 11 weeks. Efficacy was assessed with the Positive and Negative Syndrome Scale (PANSS); Clinical Global Impression (CGI) Severity of Illness and Global Improvement scores; and the Calgary Depression Scale for Schizophrenia (CDSS). Clinical benefit and tolerability were also assessed. RESULTS The mean modal dose of quetiapine was 505 mg/day; 509 patients switched to quetiapine from olanzapine (13%), risperidone (11%), conventional antipsychotics (37%) and combinations of antipsychotics (28%), amongst others. Significant decreases in CGI Severity of Illness and PANSS scores and a significant improvement in CDSS score resulted from the switch (all P<0.001 versus baseline). There were significant reductions in extrapyramidal symptoms (EPS) on the Simpson-Angus Scale (SAS) and Barnes Akathisia Scale (BAS) (both P<0.001 versus baseline) and a low incidence of EPS-related adverse events (4.7%). CONCLUSION Results indicate that switching to quetiapine was clinically beneficial for patients with poor efficacy or intolerable side effects on their previous antipsychotic medication.