Bioanalytical Methods
Plasma concentrations of paclitaxel were measured using a validated liquid chromatography/mass spectrometry/ mass spectrometry assay with a lower limit of quantification of 2.5 ng/mL. The calibration curve was prepared by spiking the drug free plasma with known concentrations of paclitaxel (2.5-2560.0 ng/ml) consisting of a blank sample (matrix sample processed without analyte or internal standard), a zero sample (matrix sample processed without analyte but with internal standard) and twelve non-zero plasma samples, including the LLOQ. Weighted linear regression (1/Y2) was used for the determination of paclitaxel. The back calculated concentrations of the calibration standards should be within ±15% of the nominal value except for the LLOQ for which it should be within ±20%. The coefficient of determination (R2) of calibration curve exceeded 0.99 (r > 0.99).
The ability to dilute sample originally above the upper limit of the standard curve has been demonstrated by accuracy and precision parameters during paclitaxel method validation. For those samples above highest standard should be diluted half with drug free plasma and analysed duplicating (reanalysis). Samples below the LLOQ (2.5 ng/ml) were not included in the data results.