Glucose Metabolism in Patients With Schizophrenia Treated With Olanzapine or Quetiapine: A Frequently Sampled Intravenous Glucose Tolerance Test and Minimal Model Analysis
J Clin Psychiatry 2006;67(5):789-797
© Copyright 2015 Physicians Postgraduate Press, Inc.
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Objective: Clozapine and olanzapine
treatment has been associated with insulin resistance in
nonobese schizophrenia patients. Much less is
known regarding other agents such as quetiapine.
The objective of this study was to compare matched olanzapine- and quetiapine-treated
schizophrenia patients and normal controls on measures of
Method: A cross-sectional comparison
of quetiapine-treated and olanzapine-treated nonobese (body mass index < 30.0
kg/m2) schizophrenia subjects (DSM-IV) with matched
normal controls using a frequently sampled
intravenous glucose tolerance test and nutritional
assessment was conducted from April 2002 to October
2004. Data from 24 subjects were included in the
analysis (7 quetiapine, 8 olanzapine, 9 normal controls).
Results: There was a significant
difference among groups for fasting baseline plasma
glucose concentrations (p = .02), with olanzapine
greater than normal controls (p = .01). The insulin
sensitivity index (SI) differed significantly among
groups (p = .039); olanzapine subjects exhibited
significant insulin resistance compared to normal
controls (p = .01), but there was no significant difference
for quetiapine versus olanzapine (p = .1) or quetiapine versus normal controls (p = .40). SI inversely
correlated with quetiapine dose (p = .0001) and
waist circumference (p = .03) in quetiapine-treated
subjects. Insulin resistance calculated by the
homeostasis model assessment of insulin resistance (HOMA-IR) also differed significantly
among groups (p = .03). The olanzapine group had a higher HOMA-IR level than normal
controls (p = .01). There was a significant difference in
glucose effectiveness (SG) among the groups (p = .049). SG was lower in the olanzapine
group than in the quetiapine group (p = .03) and in
the olanzapine group compared to normal controls (p = .049).
Conclusions: Our findings are consistent
with our previous report that nonobese olanzapine - treated subjects showed insulin resistance,
measured by both HOMA - IR and SI, and reduction in SG. Studies that include larger samples,
unmedicated patients, and varying durations of
antipsychotic exposure are necessary to confirm