A Novel LC–MS-MS Method With an Effective Antioxidant for the Determination of Edaravone, a Free-Radical Scavenger in Dog Plasma and its Application to a Pharmacokinetic Study

The objective of this study was to investigate the stability of edaravone in dog plasma by using an added antioxidant stabilizer, with an ultimate goal of developing and validating a sensitive, reliable and robust LC-MS-MS method for determination of edaravone in plasma samples. Edaravone was unstable in plasma, but it presented a good stability performance in the plasma with sodium metabisulfite (SMB), an effective antioxidant. The blood sample was collected in the heparinized eppendorf tube containing SMB and plasma sample was deproteinized using acetonitrile containing 20 ng/mL of phenacetin (Internal standard). The chromatographic separation was performed on a Zorbax Extend-C18 analytical column (2.1 mm × 150 mm I.D., particle size 3.5 µm, Agilent Technologies, USA). The mobile phase consisted of 0.1% formic acid in water (v/v) and methanol, and gradient elution was used. The analyte detection was performed on a triple quadrupole tandem mass spectrometer equipped with positive-ion electrospray ionization by multiple reaction ion monitoring mode of the transitions at m/z [M + H]+ 175.1 → 77.1 for edaravone, and m/z [M + H]+ 180.2 → 110.0 for phenacetin. The linearity of this method was within the concentration range of 10-1000 ng/mL for edaravone in dog plasma. The lower limit of quantification was 10 ng/mL. The relative standard deviations of intra- and inter-precision were <10%. This method was successfully employed in the pharmacokinetics evaluation of edaravone in beagle dogs after intravenous administration.