Development and validation of an UPLC–MS/MS method for the quantification of tamoxifen and its main metabolites in human scalp hair

• Published in: Journal of pharmaceutical and biomedical analysis Vol. 114; pp. 416 - 425
• Main Authors: Drooger, Jan C., Jager, Agnes, Lam, Mei-Ho, den Boer, Mathilda D., Sleijfer, Stefan, Mathijssen, Ron H.J., de Bruijn, Peter
• Format: Journal Article
• Language: English
• Published: England Elsevier B.V 10-10-2015
• Subjects: 4-Hydroxy-tamoxifen; Adult; Aged; Calibration; Chromatography, High Pressure Liquid - methods; Endoxifen; Female; Hair - chemistry; Hair - drug effects; Humans; Hydrogen-Ion Concentration; Light; Limit of Detection; Middle Aged; N-Desmethyl-tamoxifen; Quality Control; Reproducibility of Results; Scalp - chemistry; Scalp - drug effects; Scalp hair; Tamoxifen; Tamoxifen - analogs & derivatives; Tamoxifen - analysis; Tandem Mass Spectrometry - methods; Ultraviolet Rays; UPLC–MS/MS; 4-Hydroxy-tamoxifen; Scalp hair; Endoxifen; N-Desmethyl-tamoxifen; Tamoxifen; UPLC–MS/MS
• ISSN: 0731-7085; 1873-264X
• DOI: 10.1016/j.jpba.2015.06.018

•Analysis of hair segments is a non-invasive method for measuring drug levels over time.•Adequate managing of hair samples before performing the analyses is important.•UPLC–MS/MS method for quantification of tamoxifen and its metabolites in scalp hair.•Degradation of tamoxifen and its metabolites in hair by irradiation with UV light.
The aim of this study was to validate an earlier developed high-performance highly sensitive ultra performance liquid chromatography/tandem mass spectrometry (UPLC–MS/MS) method for quantification of tamoxifen and its three main metabolites (N-desmethyl-tamoxifen, 4-hydroxy-tamoxifen and 4-hydroxy-N-desmethyl-tamoxifen) in scalp hair. This non-invasive method might, by segmental analysis of hair, be useful in the determination of the concentration of drugs and its metabolites over time, which can be used to study a wide variety of clinical relevant questions. Hair samples (150–300 hair strands, cut as close to the scalp as possible from the posterior vertex region of the head) were collected from female patients taking tamoxifen 20mg daily (n=19). The analytes were extracted using a liquid–liquid extraction procedure with carbonate buffer at pH 8.8 and a mixture of n-hexane/isopropranol method, followed by UPLC–MS/MS chromatography, based on an earlier validated method. The calibration curves were linear in the range of 1.00–200pmol for tamoxifen and N-desmethyl-tamoxifen, with lower limit of quantitation of 1.00pmol and 0.100–20.0pmol with lower limit of quantitation of 0.100pmol for endoxifen and 4-hydroxy-tamoxifen. Assay performance was fair with a within-run and between-run variability less than 9.24 at the three quality control samples and less than 15.7 for the lower limit of quantitation. Importantly, a steep linear decline was observed from distal to proximal hair segments. Probably, this is due to UV exposure as we showed degradation of tamoxifen and its metabolites after exposure to UV-light. Furthermore, higher concentrations of tamoxifen were found in black hair samples compared to blond and brown hair samples. We conclude that measurement of the concentration of tamoxifen and its main metabolites in hair is possible, with the selective, sensitive, accurate and precise UPLC–MS/MS method. However, for tamoxifen, it seems not possible to determine exposure over time with segmental analysis of hair, probably largely due to the effect of UV irradiation. Further research should therefore focus on quantification of other anticancer drugs, in segmented scalp hair, that are less sensitive to UV irradiation.