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March 3, 2004

Olanzapine vs Haloperidol for Treatment of Schizophrenia—Reply

Author Affiliations

Letters Section Editor: Stephen J. Lurie, MD, PhD, Senior Editor.

JAMA. 2004;291(9):1064. doi:10.1001/jama.291.9.1065-d

In Reply: Drs Volavka and Citrome suggest that some patients in our study may have previously failed to improve with atypical antipsychotic drugs, thus biasing our results in favor of a negative effect of olanzapine. We think this conclusion is unlikely. We did not find that olanzapine was less effective in our study than in others, but rather that haloperidol was so much better, probably because we provided prophylactic benztropine. In fact, at entry into our study, 40% of patients were receiving an atypical antipsychotic, 37% were receiving haloperidol, and the rest were receiving other conventional agents. If anything, this would have biased the results against haloperidol, not olanzapine. Volavka et al1 have previously acknowledged that the findings of their study favoring olanzapine were invalid because " . . . we included patients who had failed to respond to haloperidol. However, those who showed a clear failure to respond to clozapine, olanzapine or risperidone were excluded. This selection bias, shared with many other studies, would be expected to result in data that tend to show superior efficacy of atypical antipsychotics."

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