Validated LC-MS/MS method for quantitative determination of rasagiline in human plasma and its application to a pharmacokinetic study.

A highly sensitive liquid chromatography-tandem mass spectrometric (LC-MS/MS) method has been developed to determine rasagiline in human plasma. The analytical method utilized liquid-liquid extraction of plasma with n-hexane-dichloromethane-isopropanol (20:10:1, v/v/v). Separation of analyte and the internal standard (IS) pseudoephedrine was performed on a Zorbax Extend C(18) column (150 mm x 4.6 mm, 5 microm) with a mobile phase consisting of acetonitrile-5 mM ammonium acetate-acetic acid (40:60:0.05, v/v/v) at a flow rate of 0.5 mL/min. The API 4000 triple quadrupole mass spectrometer was operated in multiple reaction monitoring mode via positive electrospray ionization interface using the transitions m/z 172.1-->m/z (117.1+115.1) for rasagiline, and m/z 166.0-->m/z 148.1 for the internal standard. The method was linear over the concentration range of 0.020-50.0 ng/mL. The intra- and inter-day precisions were less than 11.2% in terms of relative standard deviation (R.S.D.), and the accuracy was within +/-6.4% in terms of relative error (RE). The lower limit of quantification (LLOQ) was identifiable and reproducible at 0.020 ng/mL with acceptable precision and accuracy. The mean extraction-efficiency at three concentrations was 95.6+/-7.0%, 97.9+/-3.0% and 95.3+/-8.3%. The validated method offered increased sensitivity (10 times higher than those reported) and wide linear concentration range. This method was successfully applied for the evaluation of pharmacokinetics of rasagiline after single oral doses of 1, 2 and 5mg rasagiline to 12 Chinese healthy volunteers.