title: Development, validation and clinical application of a HPLC-FL method for CYP2D6 phenotyping in South Brazilian breast cancer patients.
abstract: OBJECTIVE
  To develop and validate a method for determination of dextromethorphan (DMT) and dextrorphan (DTP) in plasma samples using HPLC-FL and to apply it to CYP2D6 phenotyping of a population from the South of Brazil.
  
  
  METHODS
  Samples were prepared by hydrolysis and liquid-liquid extraction. Analysis was conducted in a reversed phase column, with isocratic elution and fluorescence detection. One hundred and forty patients being treated with tamoxifen were given 30 mg of dextromethorphan and their CYP2D6 phenotypes were determined on the basis of [DMT]/[DTP] metabolic ratios in plasma samples collected after 3h.
  
  
  RESULTS
  Total chromatography running time was 12 min. Precision (CV%) was below 9.7% and accuracy was between 92.1 and 106.9%. The lower limits of quantification were 1 ng mL(-1) for DMT and 10 ng mL(-1) for DTP. Mean extraction yield of analytes was 86.6%. Mean age of patients was 55.7 years. Phenotype frequencies were as follows: 7.1% poor metabolizers, 13.6% intermediate metabolizers, 77.1% extensive metabolizers and 2.1 ultra-rapid metabolizers. Metabolic ratios for patients on strong (n=11) and weak (n=16) CYP2D6 activity inhibitors were different from each other and also different from ratios for patients not taking enzyme inhibitors (n=113).
  
  
  CONCLUSIONS
  A sensitive method for determination of dextromethorphan and its metabolite in plasma samples was developed and successfully applied, providing evidence of the impact that CYP2D6 inhibitors have on the enzyme's metabolic capacity.
authors.affiliation: Pós-graduação em Ciências Médicas, Faculdade de Medicina, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil; Instituto de Ciências da Saúde, Universidade Feevale, Novo Hamburgo, RS, Brazil. Electronic address: marinaantunes@feevale.br.
authors.forename: Marina Venzon
authors.initials: MV
authors.lastname: Antunes
authors.affiliation: Instituto de Ciências da Saúde, Universidade Feevale, Novo Hamburgo, RS, Brazil.
authors.forename: Dilana Elisabeth
authors.initials: DE
authors.lastname: Staudt
authors.affiliation: Instituto de Ciências da Saúde, Universidade Feevale, Novo Hamburgo, RS, Brazil.
authors.forename: Suziane
authors.initials: S
authors.lastname: Raymundo
authors.affiliation: Instituto de Ciências da Saúde, Universidade Feevale, Novo Hamburgo, RS, Brazil.
authors.forename: Vanessa
authors.initials: V
authors.lastname: de Oliveira
authors.affiliation: Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil.
authors.forename: Gustavo
authors.initials: G
authors.lastname: Gössling
authors.affiliation: Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil.
authors.forename: Rafaela
authors.initials: R
authors.lastname: Pirolli
authors.affiliation: Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil.
authors.forename: Jorge Villanova
authors.initials: JV
authors.lastname: Biazús
authors.affiliation: Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil.
authors.forename: José Antônio
authors.initials: JA
authors.lastname: Cavalheiro
authors.affiliation: Hospital Moinhos de Vento, Porto Alegre, RS, Brazil.
authors.forename: Daniela Dornelles
authors.initials: DD
authors.lastname: Rosa
authors.affiliation: Pós-graduação em Ciências Médicas, Faculdade de Medicina, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil; Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil.
authors.forename: Gilberto
authors.initials: G
authors.lastname: Schwartsmann
authors.affiliation: Instituto de Ciências da Saúde, Universidade Feevale, Novo Hamburgo, RS, Brazil.
authors.forename: Rafael
authors.initials: R
authors.lastname: Linden
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000627:therapeutic use; D001938:Brazil; D001943:Breast Neoplasms / Q000188:drug therapy / Q000201:enzymology*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D019389:Cytochrome P-450 CYP2D6 / Q000378:metabolism*; D005260:Female; D006801:Humans; D013629:Tamoxifen / Q000627:therapeutic use
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D013629:Tamoxifen; D019389:Cytochrome P-450 CYP2D6
keywords: CYP2D6; Dextromethorphan; Dextrorphan; HPLC-FL; Phenotyping; Tamoxifen