To the Editor.—
Davidson et al1 reported that plasma homovanillic acid (pHVA) concentrations decreased in a group of neuroleptic responders (n=7) but were unchanged in nonresponders (n=13). Within the framework of a large experiment,2 we collected analogous data. To replicate their results, we emulated their analyses with our data set.Our experiment2 used 176 acutely exacerbated schizophrenic or schizoaffective patients. After a placebo period, they were randomly assigned to one of three plasma levels of haloperidol for 6 weeks. Weekly measures included haloperidol plasma levels, the Brief Psychiatric Rating Scale (BPRS), Clinical Global Impression (CGI), and, in a subset of patients, pHVA (assayed with a modification of a published method3 using gas chromatography/mass spectroscopy and deuterated HVA as an internal standard).Emulating the sampling criteria of Davidson et al,1 we selected 28 schizophrenic patients who had a minimum of four points on the CGI at baseline
VOLAVKA J, DOUYON R, CONVIT A, CZOBOR P, COOPER TB. Neuroleptic Treatment, Symptoms of Schizophrenia, and Plasma Homovanillic Acid Concentrations Revisited. Arch Gen Psychiatry. 1992;49(12):999–1000. doi:10.1001/archpsyc.1992.01820120087017
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