Investigational study of tamoxifen phase I metabolites using chromatographic and spectroscopic analytical techniques.

A comprehensive overview is presented of currently known phase I metabolites of tamoxifen consisting of their systematic name and molecular structure. Reference standards are utilized to elucidate the MS(n) fragmentation patterns of these metabolites using a linear ion trap mass spectrometer. UV-absorption spectra are recorded and absorption maxima are defined. Serum extracts from ten breast cancer patients receiving 40mg tamoxifen once daily were qualitatively analyzed for tamoxifen phase I metabolites using a liquid chromatography-tandem mass spectrometry set-up. In total, 19 metabolites have been identified in these serum samples. Additionally a synthetic method for the preparation of the putative metabolite 3',4'-dihydroxytamoxifen is described.