@article {Poon1119, author = {G K Poon and Y C Chui and R McCague and P E L{\l}nning and R Feng and M G Rowlands and M Jarman}, title = {Analysis of phase I and phase II metabolites of tamoxifen in breast cancer patients.}, volume = {21}, number = {6}, pages = {1119--1124}, year = {1993}, publisher = {American Society for Pharmacology and Experimental Therapeutics}, abstract = {This study describes the application of LC/MS/MS to the determination of phase I and phase II metabolites of tamoxifen in urine and plasma samples of breast cancer patients. In the plasma extracts, in addition to the parent drug and N-desmethyltamoxifen, a minor metabolite tamoxifen N-oxide was identified for the first time in human. Four intact glucuronides of tamoxifen metabolites were isolated in the 24-hr posttreatment urine sample. They were the glucuronides of 4-hydroxytamoxifen, 4-hydroxy-N-desmethyltamoxifen, dihydroxytamoxifen, and a monohydroxy-N-desmethyltamoxifen. Hydroxylation followed by glucuronidation is a well-established metabolic route of tamoxifen, and this study describes for the first time direct analyses of these metabolites in human urine samples using on-line LC tandem MS.}, issn = {0090-9556}, URL = {https://dmd.aspetjournals.org/content/21/6/1119}, eprint = {https://dmd.aspetjournals.org/content/21/6/1119.full.pdf}, journal = {Drug Metabolism and Disposition} }