A Simple and Robust LC–MS/MS Method for Measuring Sirolimus and Everolimus in Whole Blood

Therapeutic drug monitoring of immunosuppressants sirolimus and everolimus is mandatory and liquid chromatography tandem mass spectrometry (LC–MS/MS) is the preferred technology for the measurement. Due to the high hydrophobicity these analytes bind to reverse-phase columns tightly and need column heating to elute. Column heating not only requires extra instrument preparation but also causes permanent column damage if the heater is left on while elution pumps stop by the end of the run. The primary improvement in the current method was to elute the analytes at room temperature using special buffers. This new LC–MS/MS method has been validated for clinical use and offers improved simplicity and robustness by eliminating column heating yet with high sensitivity, precision and accuracy.