title: Interindividual variabilities in haloperidol interconversion and the reduced haloperidol/haloperidol ratio.
abstract: Metabolism of haloperidol in humans includes N-dealkylation to inactive metabolites and reduction to reduced haloperidol; reduced haloperidol is also oxidized back to haloperidol. A single 0.5 mg/kg (0.00133 mmol/kg) oral dose of haloperidol and reduced haloperidol was administered to seven Chinese schizophrenics in a randomized crossover manner separated by a 2-week interval. The clearance values for the different metabolic pathways of haloperidol and reduced haloperidol were determined. There were differences up to 10-fold in both oxidation and reduction capacities. There were also interindividual variabilities in the elimination of reduced haloperidol (0.37 +/- 0.20 L/hr/kg) and the N-dealkylation pathway (0.74 +/- 0.36 L/hr/kg). Four weeks after the single-dose study, the same patients also received haloperidol (10 mg) twice daily for 4 weeks. The reduced haloperidol to haloperidol concentration ratio (0.40 +/- 0.16) after the 4-week therapy is related to individual variabilities in the interconversion process and the N-dealkylation pathway of haloperidol.
authors.affiliation: Department of Pharmacology, University of Texas Health Science Center, San Antonio 78284-6220.
authors.forename: Y W
authors.initials: YW
authors.lastname: Lam
authors.forename: W H
authors.initials: WH
authors.lastname: Chang
authors.forename: M W
authors.initials: MW
authors.lastname: Jann
authors.forename: H
authors.initials: H
authors.lastname: Chen
mesh_terms: D000328:Adult; D001711:Biotransformation; D006220:Haloperidol / Q000378:metabolism* / Q000493:pharmacokinetics / Q000627:therapeutic use; D006801:Humans; D008297:Male; D008433:Mathematics; D008657:Metabolic Clearance Rate; D008954:Models, Biological; D012559:Schizophrenia / Q000097:blood / Q000188:drug therapy / Q000378:metabolism
chemical_list: D006220:Haloperidol