Development and validation of a liquid chromatography-tandem mass spectrometry assay for determination of raloxifene and its metabolites in human plasma.

This paper describes the development and validation of a method for the detection of raloxifene (Ral) and its two glucuronide metabolites, raloxifene-6-glucuronide (M1) and raloxifene-4'-glucuronide (M2), in human plasma samples. Both glucuronides were synthesized enzymatically, purified and used as authentic standards. The assay involves a simple solid phase extraction (SPE) procedure of 0.5 mL of human plasma and subsequent analysis by LC-MS-MS. The recoveries were higher than 71% and chromatographic separation of all the analytes was accomplished in less than 7 min. Linear ranges (r(2)>0.99) were found from 0.200 to 340 microg/L, from 1.600 to 2720 microg/L and from 0.088 to 60.00 microg/L, for M1, M2 and Ral, respectively. The limits of detection achieved were 8, 11 and 6 ng/L for M1, M2 and Ral, respectively. The method presented was successfully applied to a genetic polymorphism study of 47 plasma samples from women taking Evista (raloxifene hydrochloride).