SOLID-PHASE EXTRACTION AND HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY OF TAMOXIFEN AND ITS DEMETHYLATED METABOLITES IN PLASMA

A reversed-phase high performance liquid chromatography method (HPLC) has been developed for the identification and the quantitation of tamo xifen, desmethyltamoxifen and didesmethyltamoxifen in plasma using a s olid phase extraction. A Waters Symmetry C8 3.5 mu m column (4.6 x 100 nun) was used, with a mobile phase of 50% acetonitrile in 100 mM ammo niutn acetate buffer at pH 5.2. Analysis of the plasma samples was car ried out at concentrations ranging from 30 to 500 ng/ml. The solutes w ere detected at 238 nm with a detection limit for tamoxifen and its de methylated metabolites as low as 5 ng/ml. Such procedures can be routi nely applied to the determination of tamoxifen and its two demethylate d metabolites in plasma from patients undergoing tamoxifen therapy.