Monthly Administration of Long-Acting Injectable Risperidone and Striatal Dopamine D<sub>2</sub> Receptor Occupancy for the Management of Schizophrenia
J Clin Psychiatry 2008;69(8):1281-1286
© Copyright 2017 Physicians Postgraduate Press, Inc.
Purchase This PDF for $40.00
If you are not a paid subscriber, you may purchase the PDF.
(You'll need the free Adobe Acrobat Reader.)
Receive immediate full-text access to JCP. You can subscribe to JCP online-only ($86) or print + online ($156 individual).
With your subscription, receive a free PDF collection of the NCDEU Festschrift articles. Hurry! This offer ends December 31, 2011.
If you are a paid subscriber to JCP and do not yet have a username and password, activate your subscription now.
As a paid subscriber who has activated your subscription, you have access to the HTML and PDF versions of this item.
Click here to login.
Did you forget your password?
Still can't log in? Contact the Circulation Department at 1-800-489-1001 x4 or send email
Objective: Long-acting risperidone
administered intramuscularly biweekly is approved for
the management of schizophrenia. However, dosing
of long-acting antipsychotics is frequently extended
in clinical practice, and a recent clinical trial has
lent support to monthly dosing of long-acting
risperidone. The objective of this positron
emission tomography (PET) study was to examine the
striatal dopamine D2 binding of long-acting
risperidone administered intramuscularly once a month.
Method: Following at least 3
maintenance monthly injections of 50 mg long-acting
risperidone, 7 patients with a DSM-IV diagnosis of schizophrenia or schizoaffective disorder
underwent PET using [11C]raclopride to measure
D2 binding potential within 4 days of the next
scheduled injection. Data were collected from May
to October 2003. This PET study was part of a
larger 52-week clinical study wherein individuals
received long-acting risperidone once monthly over
a 1-year interval. One-year follow-up data were obtained from the 52-week parent investigation.
Results: The mean ± SD
D2 receptor occupancy was 56% ± 24% (range, 29%-82%). Of note,
there were 4 subjects with less than 60%
D2 occupancy, none of whom relapsed over the course of the
1-year follow-up. The mean ± SD total plasma
level of risperidone plus 9-hydroxyrisperidone was
16.6 ± 12.3 ng/mL (range, 5.7-40.8).
Conclusion: As with plasma levels, there
was considerable variability in D2 occupancy levels
for individuals receiving long-acting risperidone.
This work suggests a possibility that sustained
D2 occupancy at or above the accepted threshold with
acute clinical response may not be necessary to
maintain response, a hypothesis with important clinical
implications as we consider antipsychotic dosing
and future antipsychotic development.
Trial Registration: clinicaltrials.gov