LC-MS/MS method for simultaneous quantification of Everolimus and Sirolimus

In order to detect low Sirolimus and Everolimus concentrations, a new liquid chromatography-tandem mass spectrometry was developed. It is a chlorobutane extraction from total EDTA blood samples. It is validated according to the recommendations of the Food and Drug Administration (FDA) in the range of 1 to 50 mu g/L. Limit of detection (LOD) and quantification (LOQ) are 0.5 mu g/L and 1 mu g/L, respectively. Inter-assay accuracy and imprecision respectively range from 98.5 to 119.3% and 2.9 to 18.2% for Sirolimus and from 93.4 to 118.7% and 4.8 to 10.2% for Everolimus. A correlation study performed on 50 patients between this method and immunological methods used in routine shows a negative bias of 1.5 mu g/L for Everolimus and 0.8 mu g/L for Sirolimus. The method described here being a LC-MS/MS method, sensitive, specific, fast and precise may replace the current immunological methods used in our laboratory. (C) 2012 Elsevier Masson SAS. All rights reserved.