The Effects of Olanzapine on the 5 Dimensions of Schizophrenia Derived by Factor Analysis: Combined Results of the North American and International Trials
J Clin Psychiatry 2001;62:757-771
© Copyright 2014 Physicians Postgraduate Press, Inc.
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Background: The choice of drug to treat a
patient with schizophrenia is one of the most critical clinical
decisions. Controversy exists on the differential efficacy of
Data Sources and Study Selection: Raw data from
all 4 registrational double-blind, random-assignment studies of
olanzapine compared with placebo or haloperidol were obtained
from Eli Lilly and Company for this meta-analysis.
Method: Analysis of covariance of the
intent-to-treat last-observation-carried-forward endpoint scores
was used to assess efficacy on Brief Psychiatric Rating Scale
(BPRS) and Positive and Negative Syndrome Scale (PANSS) total
scores and the 5 factors derived by factor analysis (negative
symptoms, positive symptoms, disorganized thoughts,
impulsivity/hostility, and anxiety/depression).
Results: Olanzapine produced a statistically
significantly greater reduction in schizophrenic symptoms than
haloperidol (p < .05) on total scores on the BPRS and PANSS on
each of the 5 factors as well as on almost all items. Olanzapine
induced a response at a rate equal to that induced by haloperidol
in the first few weeks, but by the end of the study produced a
greater percentage of responders. Compared with haloperidol,
olanzapine produced a somewhat greater response on symptoms
responsive to haloperidol, but a markedly better response on
symptoms unresponsive to haloperidol. This difference favoring
olanzapine occurred to an equal degree in all subgroups examined.
The incidence of parkinsonism or akathisia following olanzapine
treatment was extremely low and not statistically distinguishable
Conclusion: Olanzapine produced a greater
improvement than haloperidol particularly by benefiting a much
larger number of items or factors. Extrapyramidal side effects
and akathisia during olanzapine treatment were statistically
indistinguishable from effects seen with placebo.