Extrapyramidal symptom profiles assessed with the Drug-Induced Extrapyramidal Symptom Scale: comparison with Western scales in the clinical double-blind studies of schizophrenic patients treated with either olanzapine or haloperidol.

The superiority of olanzapine to haloperidol with respect to a decreased incidence of treatment-emergent extrapyramidal syndromes (EPS) in patients with schizophrenia was demonstrated in studies conducted in both Japan and Western countries. EPS measurements used in Western countries included the Simpson-Angus, Barnes akathisia and the Abnormal Involuntary Movement Scale, while the Drug-Induced Extrapyramidal Symptom Scale (DIEPSS) was used in Japan. The aim of this study was to clarify how the DIEPSS captures EPS profiles. The baseline prevalence and treatment-emergent incidence of EPS in Japanese schizophrenic patients treated with olanzapine or haloperidol were retrospectively compared as assessed by the DIEPSS to the prevalence and incidence of EPS in primarily Caucasian schizophrenic patients who were treated with olanzapine or haloperidol. Specifically, the prevalence and incidence of dyskinesia, akathisia and parkinsonism were compared between the Japanese trial and an international trial to examine if appropriate definitions using the DIEPSS can be derived assuming that a comparable prevalence and incidence of the syndromes would be observed when any differences in residual antipsychotic exposure at the initiation of study treatment were accounted for. For the incidence of all EPS syndromes, odds ratios were observed to be similar between the two studies, indicating that appropriate criteria for the clinical diagnosis of the EPS syndromes could be established based on the DIEPSS. This preliminary and retrospective work suggests that the DIEPSS can be used to operationally define the presence or absence, and make the clinical diagnosis, of specific EPS syndromes.