Am J Psychiatry 1997; 154:1243-1247
Copyright © 1997 by American Psychiatric Association
Time to clozapine response in a standardized trial
RR Conley, WT Carpenter Jr and CA Tamminga
Maryland Psychiatric Research Center, University of Maryland School of Medicine, Baltimore, USA.
OBJECTIVE: The authors sought to determine the time to clozapine response
in treatment-refractory patients with schizophrenia. METHOD: Antipsychotic
response to a clozapine trial was examined in 50 treatment-refractory
schizophrenic inpatients. Subjects were treated with clozapine for at least
12 months, regardless of response status, according to a standardized,
increasing dose protocol. Behavioral changes were measured through monthly
assessments with the Brief Psychiatric Rating Scale. RESULTS: Thirty-four
subjects (68%) met clinical response criteria by the end of the trial.
Response was achieved at a mean dose of 468 mg/day (SD = 168). The dose of
30 (88%) of the responding patients was 600 mg/day or less. The mean time
to response was 82 days (SD = 100, range = 10-401). It took an average of
60 days (SD = 87) for subjects to reach the dose at which clozapine
response was achieved. Once this dose was reached, the average response
time was 17 days (SD = 14, range = 2-56). All 34 subjects who responded met
criteria within 8 weeks of a clozapine dose escalation. No late response
was found in the remaining 16 subjects despite a mean follow- up period of
75 weeks (SD = 50). CONCLUSIONS: In this study, all patients who responded
to clozapine did so within 8 weeks of a change in dose. Thus, there appears
to be little clinical gain in prolonging exposure to clozapine beyond 8
weeks at any particular dose if no response is seen.
