Dose-related effects of amisulpride on five dimensions of psychopathology in patients with acute exacerbation of schizophrenia

The present analysis investigated symptom-specific dose-response relationships of the atypical antipsychotic amisulpride (AMI) in schizophrenic patients. The effects of different AMI doses on five different symptom dimensions of the Brief Psychiatric Rating Scale (BPRS) were analyzed. Results on global efficacy and safety parameters have been previously published. Four AMI doses (100 mg/day [AMI100], 400 mg/day [AMI400], 800 mg/day [AMI800], 1200 mg/day) were compared with 16 mg haloperidol (HAL16) in a multicenter, double-blind, randomized, parallel-group, 4-week trial. A total of 319 patients with acute exacerbation of schizophrenia (DSM-III-R) were included. AMI100 was compared with the other AMI doses, and HAL16 was compared with all AMI dosage groups. Response on BPRS factors defined as ≥ 40% improvement and ORs were computed. An optimal AMI dose was calculated for each BPRS factor based on linear and quadratic regression. For all BPRS factors, inverted u-shaped dose-response curves emerged (r2 > 95%). The estimated AMI dose optimum for the BPRS factors activation/ agitation (760 mg), thought disturbances (716 mg), and hostility/suspiciousness (694 mg) was higher than that for anergia/negative symptoms (584 mg) and depression/anxiety (672 mg). Significant differences (p < 0.05) were found for AMI400/800 versus AMI100 (thought disturbances, hostility/ suspiciousness), for AMI400/800 versus HAL16 (depression/anxiety, thought disturbances, hostility/suspiciousness), and for AMI400 versus HAL16 (anergia/negative symptoms). ORs for response of the BPRS factors depression/anxiety, anergia/negative symptoms, and hostility/suspiciousness were highest under treatment with AMI400 compared to AMI100 and HAL16. For the BPRS factors thought disturbances and activation/agitation, the highest response chance emerged under AMI800 compared to AMI100 or HAL16. AMI seems to show the best clinical efficacy in acutely schizophrenic patients in a moderate dose (400-800 mg/day), with a somewhat lower dose optimum for negative than for positive symptoms. The present finding of distinct dose-response relationships of AMI regarding the BPRS dimensions is in accordance with studies on the mechanism of action of AMI and provides a useful rationale for the clinical treatment of schizophrenic patients with AMI.