Stability of sirolimus (Rapamycin) in whole blood

The effects of storage time (0 - 8 days), temperature (4 degrees C and 30 d egrees C in dark and light), and freeze-thaw cycles on the stability of sir olimus in blood were examined. Sirolimus quantification was undertaken usin g HPLC-electrospray-tandem mass spectrometry. Whole blood samples supplemen ted with sirolimus (5.0, 15.0, and 30.0 mu g/L) and pooled renal and heart transplant samples were found to be stable during the 8 days under all cond itions (<10% decrease in concentration). No significant difference was obse rved in sirolimus concentration between freshly collected patient samples a nd sirolimus-supplemented samples (5.0, 15.0, and 30.0 mu g/L) after three freeze-thaw cycles (p > 0.198). In conclusion, blood samples can be transpo rted with or without cooling for up to 8 days without sirolimus results bei ng compromised. The reanalysis of sirolimus samples, which may entail freez e-thaw cycles, can be undertaken if the number of cycles is three or less.