Measurement of rapamycin in whole blood using reverse-phase high-performance liquid chromatography

Rapamycin (RAPA) is an immunosuppressant with a potency similar to FK 506 and up to 100-fold greater than cyclosporine. To date, no data have been reported on the pharmacokinetics and disposition of the drug, primarily due to a lack of suitable methods for its analysis. We describe here an evaluation of a reverse-phase high-performance liquid chromatographic (HPLC) method for analysis of the drug in whole blood. The method showed excellent analytical recovery of the drug, close to 100%. The sensitivity method was found to be 1.0 micrograms/L with between-run coefficients of variation of 14.4% and 9.8% at 10 and 50 mg/L. The stability of RAPA was investigated with this method in whole-blood specimens. It was found that the drug was stable for 30 days at 4 degrees C and for 55 days at -40 degrees C.