Quetiapine Extended-Release Versus Immediate-Release Formulation: A Positron Emission Tomography Study
J Clin Psychiatry 2008;69(1):81-86
© Copyright 2014 Physicians Postgraduate Press, Inc.
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Objective: The pharmacokinetic and pharmacodynamic profile of
the immediate-release (IR) formulation of quetiapine is characterized by a
rapid peak in plasma level and striatal dopamine D2 receptor
occupancy, followed by a rapid decrease to baseline levels, necessitating the
use of twice-daily dosing. An extended-release (XR) formulation of quetiapine
is currently being developed to achieve similar efficacy using a once-daily
dosing regimen. We compared the central D2 receptor binding between
the IR and XR formulations.
Method: In this open-label, crossover positron emission
tomography study using [11C]-raclopride, we compared the central D2
receptor binding potential at expected peak and trough plasma levels using
equivalent daily doses of the IR and XR formulations (300, 600, and 800 mg/day)
in 12 subjects. Data were collected from April 2002 to May 2003.
Results: The mean plasma level of quetiapine at trough was
significantly lower than that at peak for all dose groups of both formulations
except for IR 300 and 800 mg (all p values < .05), while the mean plasma level
did not differ significantly between formulations at trough and peak. The mean
occupancy at peak was significantly higher than that at trough for all dose
groups other than IR 800 mg/day (all p values < .05) and did not differ
significantly between formulations at trough and peak.
Conclusion: Once-daily dosing of the XR formulation gives peak
and trough plasma levels and central D2 receptor occupancy
comparable to twice-daily dosing of the IR formulation. These data should be
considered while determining equivalent doses, as well as switching strategies.