Stability of sirolimus (rapamycin) in whole blood

The effects of storage time (0-8 days), temperature (4 degrees C and 30 degrees C in dark and light), and freeze-thaw cycles on the stability of sirolimus in blood were examined. Sirolimus quantification was undertaken using HPLC-electrospray-tandem mass spectrometry. Whole blood samples supplemented with sirolimus (5.0, 15.0, and 30.0 microg/L) and pooled renal and heart transplant samples were found to be stable during the 8 days under all conditions (<10% decrease in concentration). No significant difference was observed in sirolimus concentration between freshly collected patient samples and sirolimus-supplemented samples (5.0, 15.0, and 30.0 microg/L) after three freeze-thaw cycles (p > 0.198). In conclusion, blood samples can be transported with or without cooling for up to 8 days without sirolimus results being compromised. The reanalysis of sirolimus samples, which may entail freeze-thaw cycles, can be undertaken if the number of cycles is three or less.