Flupirtine Determination in Human Blood Plasma by HPLC with Mass-Spectrometric Detection and its Application to Pharmacokinetic Studies

A validated method for quantitative determination of flupirtine in human blood plasma using liquid chromatography combined with tandem mass spectrometry (HPLC-MS/MS) was proposed. Biological samples were prepared by precipitating proteins using MeOH. The chromatographic separation used a Zorbax Eclipse Plus C18 column with gradient elution. A Shimadzu 8040 triple quadrupole mass spectrometer in multiple-reaction-monitoring mode (+MRM) with chemical ionization at atmospheric pressure (APCI) was used to determine the molecular ion of flupirtine with m/z 305.2. Acalibration curve for flupirtine was linear (R = 0.994) in the concentration range 25 – 2,500 ng/mL with a lower detection limit of 25 ng/mL. Validation of the method indicated that it was highly sensitive, specific, accurate, and precise and that the analyte was stable. The method was successfully applied to comparative pharmacokinetic studies of drugs containing flupirtine.