Abstract

Background: Sirolimus is an immunosuppressant used in solid organ transplantation. Due to variable individual pharmacokinetics and narrow therapeutic ranges, therapeutic drug monitoring (TDM) is critical to the success of post-transplantation patient care. We developed a rapid method quantifying whole blood sirolimus using liquid chromatography-tandem mass spectrometry (LC-MS/MS) with an automated online extraction technology.

Methods: Whole blood (100 μL) was mixed with a precipitation solution containing internal standard (32-desmethoxyrapamycin) and centrifuged at 15,634×g for 10 min. The supernatant (50 μL) was injected onto a turbulent flow preparatory column and then a C18 analytical column. The mass spectrometer was set for positive electrospray to monitor the ammonium adducts.

Results: Analytical time was 4 min/injection. Inter- and intra-assay variation coefficients across three concentration levels ranged from 2.3% to 7.4%. The method was linear from 1.0 to 100.0 ng/mL with an accuracy of 93.3%–100.0%. No carryover was detected from samples at 313.6 ng/mL. There was no obvious ion suppression from patient samples or interference from other commonly used immunosuppressants. Good correlation with an in-house commercial LC-MS was observed.

Conclusions: The LC-MS/MS method coupled with turbulent flow technology is rapid and efficient in TDM of whole blood sirolimus.

Clin Chem Lab Med 2008;46:1631–4.