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Chlorpromazine Equivalent Doses for the Newer Atypical Antipsychotics

Scott W. Woods, M.D.

Background: Several clinical and research applications require an estimation of therapeutic dose equivalence across antipsychotic medications. Since the advent of the newer atypical antipsychotics, new dose equivalent estimations have been needed.

Method: The reported minimum effective dose was identified for each newer atypical antipsychotic medication and for haloperidol across all available fixed-dose placebo-controlled studies. Reported minimum effective dose equivalence ratios to haloperidol were then converted to chlorpromazine equivalents using the "2 mg of haloperidol equals 100 mg of chlorpromazine" convention.

Data Sources and Study Selection: To identify the fixed-dose studies, the following sources were searched until June 2002: MEDLINE, the bibliographies of identified reports, published meta-analyses and reviews, Cochrane reviews, Freedom of Information Act material available from the Food and Drug Administration, and abstracts from several scientific meetings from 1997 to 2002.

Results: Doses equivalent to 100 mg/day of chlorpromazine were 2 mg/day for risperidone, 5 mg/day for olanzapine, 75 mg/day for quetiapine, 60 mg/day for ziprasidone, and 7.5 mg/day for aripiprazole.

Conclusion: These equivalency estimates may be useful for clinical and research purposes. The source of the dose equivalency estimation is evidence-based and consistent across medication.

(J Clin Psychiatry 2003;64:663-667)

Received Aug. 21, 2002; accepted Dec. 25, 2002. From the Department of Psychiatry, Yale University School of Medicine, Connecticut Mental Health Center, New Haven.

Supported by U.S. Public Health Service (USPHS) grant R01 MH61008.

The author has received grant/research support from Eli Lilly and Janssen.

Corresponding author and reprints: Scott W. Woods, M.D., Department of Psychiatry, Yale University School of Medicine, 34 Park St., New Haven, CT 06519 (e-mail: