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August 1985

The Interpretation of Plasma Haloperidol Concentrations

Author Affiliations

Neuropsychiatry Branch National Institute of Mental Health Intramural Research Program Saint Elizabeths Hospital William A. White Building Washington, DC 20032

Arch Gen Psychiatry. 1985;42(8):838-839. doi:10.1001/archpsyc.1985.01790310106016

To the Editor.—  The recent study by Smith et al1 regarding plasma haloperidol concentrations and clinical response addressed an important issue in the treatment of schizophrenia. Their statistical analysis of the clinical data, however, illustrates the complexities involved in balancing mathematical rigor against the reasonable interpretation of clinical observations.The authors assumed that the neuroleptic-induced course of clinical improvement in symptoms of psychosis is linear and used this assumption to "estimate" Basic Psychiatric Research Scale (BPRS) scores for patients on days 0 and 24 of treatment. Clinical experience, however, indicates that in many patients response is "nonlinear," with a frequently observed pattern being one of more rapid improvement early in treatment followed by a more gradual phase. Furthermore, the linear model of the relationship of improvement vs time would, if extended, produce either a negative rating in the case of a patient whose condition is improving or a