Efficacy and tolerability of quetiapine in patients with schizophrenia who switched from haloperidol, olanzapine or risperidone

A post hoc analysis of the SPECTRUM trial was carried out to evaluate whether the improvements in efficacy and tolerability gained on switching to quetiapine occurred consistently for patients previously treated with either: haloperidol (n = 43); olanzapine (n = 66); or risperidone (n = 55) monotherapy. Patients were initiated with quetiapine to 400 mg/day over 7 days, and then flexibly dosed (300-750 mg/day) for 11 weeks. The mean (SD) modal dose of quetiapine was 501 (138) mg/day in the haloperidol subgroup, 472 (147) mg/day in the olanzapine subgroup and 485 (141) mg/day in the risperidone subgroup at the study endpoint. Switching to quetiapine induced significant improvements from baseline in PANSS scores, with least square mean changes in total scores of -32.5, -15.4, and -18.5 for patients previously treated with haloperidol, olanzapine and risperidone, respectively, (all p < 0.001 vs baseline). Significant improvements were also noted in CDSS scores, particularly for patients clinically depressed at baseline (all p < 0.001 vs baseline). There were significant reductions in EPS on the SAS and BAS for all subgroups (all p < 0.001 vs baseline). Switching to quetiapine produced efficacy and tolerability benefits regardless of whether their previous antipsychotic was haloperidol, olanzapine or risperidone.