title: Intra- and interethnic variability in reduced haloperidol to haloperidol ratios.
abstract: Steady-state haloperidol and reduced haloperidol concentrations were measured in 250 schizophrenic patients from 4 ethnic groups: 39 Blacks, 66 Caucasians, 82 Chinese, and 63 Mexican Americans. The distribution of the reduced haloperidol to haloperidol concentration (RH/HL) ratios was bimodal in all ethnic groups, with the antimode determined by probit plot as 0.46, 0.51, 0.36, and 0.76, respectively. With these antimodes, the proportion of patients with low RH/HL ratios were 41%, 42%, 73%, and 57% in the four ethnic groups, respectively. Compared with the other three ethnic groups, in the Chinese patients the ratio was lower. The mean RH/HL ratio in the Chinese was 0.34 compared with 0.81 to 0.87 in the non-Chinese groups. In 53 patients who were treated with two or more haloperidol dosage regimens, steady-state haloperidol and reduced haloperidol drug concentrations obtained from the different regimens were positively correlated with the haloperidol dose (R = .79 and R = .62, respectively). Our data suggest not only the existence of a bimodal distribution in the RH/HL ratio, but also that the antimode separating the low and high ratio subgroups is different among the various ethnic groups.
authors.affiliation: Department of Pharmacology, University of Texas Health Science Center at San Antonio, USA.
authors.forename: Y W
authors.initials: YW
authors.lastname: Lam
authors.forename: M W
authors.initials: MW
authors.lastname: Jann
authors.forename: W H
authors.initials: WH
authors.lastname: Chang
authors.forename: H S
authors.initials: HS
authors.lastname: Yu
authors.forename: S K
authors.initials: SK
authors.lastname: Lin
authors.forename: H
authors.initials: H
authors.lastname: Chen
authors.forename: C M
authors.initials: CM
authors.lastname: Davis
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D044466:Asian People; D044383:Black People; D005006:Ethnicity; D005260:Female; D006220:Haloperidol / Q000493:pharmacokinetics*; D006801:Humans; D008297:Male; D008657:Metabolic Clearance Rate; D017058:Mexican Americans; D012559:Schizophrenia / Q000097:blood* / Q000208:ethnology; D013624:Taiwan / Q000208:ethnology; D013781:Texas; D044465:White People; D001741:Black or African American
chemical_list: D006220:Haloperidol