title: Determination of olanzapine and N-desmethyl-olanzapine in plasma using a reversed-phase HPLC coupled with coulochemical detection: correlation of olanzapine or N-desmethyl-olanzapine concentration with metabolic parameters.
abstract: BACKGROUND
  Olanzapine (OLZ) is one of the most prescribed atypical antipsychotic drugs but its use is associated with unfavorable metabolic abnormalities. N-desmethyl-olanzapine (DMO), one of the OLZ metabolites by CYP1A2, has been reported to have a normalizing action on metabolic abnormalities, but this remains unclear. Our aim was to explore the correlation between the concentrations of OLZ or DMO with various metabolic parameters in schizophrenic patients.
  
  
  METHODS
  The chromatographic analysis was carried out with a solvent delivery system coupled to a Coulochem III coulometric detector to determine OLZ and DMO simultaneously in OLZ-treated patients. The correlation between the concentration of OLZ or DMO and the metabolic parameters was analyzed by the Spearman rank order correlation method (r s).
  
  
  RESULTS
  The established analytical method met proper standards for accuracy and reliability and the lower limitation of quantification for each injection of DMO or OLZ was 0.02 ng. The method was successfully used for the analysis of samples from nonsmoking patients (n = 48) treated with OLZ in the dosage range of 5-20 mg per day. There was no correlation between OLZ concentrations and tested metabolic parameters. DMO concentrations were negatively correlated with glucose (r s = -0.45) and DMO concentrations normalized by doses were also negatively correlated with insulin levels (r s = -0.39); however, there was a marginally positive correlation between DMO and homocysteine levels (r s = +0.38).
  
  
  CONCLUSIONS
  The observed negative correlations between levels of DMO and glucose or insulin suggest a metabolic normalization role for DMO regardless of its positive correlation with a known cardiovascular risk factor, homocysteine. Additional studies of the mechanisms underlying DMO's metabolic effects are warranted.
authors.affiliation: Department of Psychiatry, Taipei Medical University-Wan Fang Medical Center, Taipei, Taiwan.
authors.forename: Mong-Liang
authors.initials: ML
authors.lastname: Lu
authors.forename: Chia-Hui
authors.initials: CH
authors.lastname: Lin
authors.forename: Yi-Chuan
authors.initials: YC
authors.lastname: Chen
authors.forename: Huai-Chih
authors.initials: HC
authors.lastname: Yang
authors.forename: Tzu-Hua
authors.initials: TH
authors.lastname: Wu
mesh_terms: D000328:Adult; D014150:Antipsychotic Agents / Q000097:blood* / Q000493:pharmacokinetics; D001569:Benzodiazepines / Q000097:blood* / Q000493:pharmacokinetics; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D000077152:Olanzapine; D010890:Pirenzepine / Q000031:analogs & derivatives* / Q000097:blood / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012559:Schizophrenia / Q000188:drug therapy / Q000378:metabolism; D055815:Young Adult
chemical_list: D014150:Antipsychotic Agents; D001569:Benzodiazepines; D010890:Pirenzepine; C425329:desmethylolanzapine; D000077152:Olanzapine