title: Determination of tamoxifen and endoxifen in dried blood spots using LC-MS/MS and the effect of coated DBS cards on recovery and matrix effects.
abstract: BACKGROUND
  We developed an HPLC-MS/MS method to quantify tamoxifen (2.5-250 ng/ml) and its metabolite (Z)-endoxifen (0.5-50 ng/ml) in dried blood spots.
  
  
  RESULTS
  Extraction recovery of both analytes from Whatman DMPK-A cards was 100% and consistent over time, however, recovery of (Z)-endoxifen from Whatman 903 cards was incomplete and increased upon storage. When SDS, a constituent of the DMPK-A coating, was present during the extraction, recovery improved. The method using DMPK-A cards was validated using bioanalytical guidelines. Additionally, influence of haematocrit (0.29-0.48 L/L), spot volume (20-50 µl) and homogeneity was within limits and both analytes were stable in DBS for at least 4 months.
  
  
  CONCLUSIONS
  The method for the quantification of tamoxifen and (Z)-endoxifen in DBS collected on DMPK-A cards was successfully validated.
authors.affiliation: Department of Pharmacy & Pharmacology, Slotervaart Hospital/The Netherlands Cancer Institute, Louwesweg 6, 1066 EC Amsterdam, The Netherlands.
authors.forename: Nynke Gl
authors.initials: NG
authors.lastname: Jager
authors.forename: Hilde
authors.initials: H
authors.lastname: Rosing
authors.forename: Jan Hm
authors.initials: JH
authors.lastname: Schellens
authors.forename: Jos H
authors.initials: JH
authors.lastname: Beijnen
mesh_terms: D018931:Antineoplastic Agents, Hormonal / Q000097:blood*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D006801:Humans; D011786:Quality Control; D012015:Reference Standards; D013629:Tamoxifen / Q000031:analogs & derivatives* / Q000097:blood*; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D018931:Antineoplastic Agents, Hormonal; D013629:Tamoxifen; C055492:4-hydroxy-N-desmethyltamoxifen